TOPIC 1: CLASSIFICATION
OF LIVING THINGS
Kingdom Plantae, Division
Coniferophyta (Conifers )
General and
Distinctive Features of the Division Coniferophyta
Explain general and
distinctive features of the division coniferophyta
Division
Coniferophyta or the conifers belong to Kingdom Plantae. These plants
are gymnosperms meaning non-flowering. They are non-flowering but seed
bearing plants. They have vascular tissues. They are woody plants
majority being evergreen trees. Few varieties are shrubs
What are the general
and distinctive features of the Division Coniferophyta?
General characteristics
1. They
have secondary growth whose thickening can be observed in cross section
of a stem revealing annual rings. Secondary Growth is the result of
growth Lateral Meristems (Vascular Cambium & Cork Cambium).
2. Most of the members of Coniferophyta live in
cool climates where they form evergreen forests. They keep their leaves
year-round.
3. They have a large amount of internodal
elongation which allows them to grow faster than the other higher plants.
4. They
are Xeromorphic, a characteristic that help to protect them from
excessive loss of water and therefore adapt survival in extreme
habitats.
5. Most are large trees while a few are shrubs
and other small plants.
6. Most of them have hard barks which protect
inner softwood.
Distinctive characteristics
1. Conifers are non-flowering but seed producing
plants.
2. They have seeds born in cones shaped
structures rather than in fruits.
3. They are gymnosperms which mean naked-seed
plants because they produce seeds in cones rather than inside an embryo.
4. The leaves are needle-shaped and have a thick
cuticle for protection and to decrease water loss.
The Structure of Pinus
Describe the structure
of pinus
Pines
are evergreen, coniferous resinous trees growing 3–80 m tall. The
bark of most pines is thick and scaly. They have needle like leaves.
Pines
are among the most well- known coniferous trees in the world. They
thrive in temperate mountainous regions, but can also survive in
tropical spots in the northern hemisphere. Pines live relatively long
time than other coniferous plants. They may live between 100 and 1,000
years
· The Stem:The
bark of most pines is thick and scaly, but some species have thin,
flaking bark. The branches are produced in regular whorls appearing like
a ring of branches arising from the same point.
· Leaves:A
cross-section of pine stem has several concentric rings with distinct
borders between each ring. The center of the stem is called pith. These
rings are called annual rings because they grow seasonally and they help
a plant to undergo secondary thickening. Generally adult pines have
needle-shaped leaves which are green and photosynthetic. The leaves are
in bundles or clusters. The leaves (cotyledons) on seedlings are borne
in a whorl of 4–24. Juvenile leaves, which follow immediately after
seedlings, have single, green leaves arranged spirally on the shoot.
They also have non- photosynthetic scale leaves, similar to bud scales.
They are arranged spirally like the juvenile leaves.
· Cones:A
cone is an organ of pines that contains the reproductive structures.
The woody cone is the female cone, which produces seeds. The male cones,
which produce pollen, are usually herbaceous and much less conspicuous.
Explain the advantages and disadvantages of the Division Coniferophyta
The advantages and disadvantages of the Division Coniferophyta
The Advantages and
Disadvantages of the Division Coniferophyta
Explain the advantages
and disadvantages of the division coniferophyta
Advantages of Conifers
1. Conifers
are very important for our economy because of their softwood, which is
used for paper and timber, as well as cedar which many people use for
their homes because of its beauty and resistance to insects. They have a
large economic use as softwood in furniture. In temperate and tropical
regions, they are fast-growing softwoods that will allow harvesting in
close succession.
2. Decoration and ceremony Many pine species make
attractive ornamentals. They are planted in parks and larger gardens.
Some varieties are suitable for smaller spaces. Pines are also
commercially grown and harvested for Christmas trees.
3. As
medicine, Pines and cypress are rich in vitamin; their branches cones
and oils can be extracted and used as nutrient supplements.
4. Due to its soft texture conifers are widely
used to manufacture Play wood.
5. As other higher plants conifers are source of
heat energy, used as firewood and charcoal.
6. Thick forests of conifers form green belts
that modify the climate.
7. Conifers form a large arena for Biological research
Ecological studies.
8. Food
uses: Some species have large seeds, called pine nuts that are
harvested and sold for cooking and baking. The soft, moist, white inner
bark (cambium) found clinging to the woody outer bark is edible and very
high in vitamins A and C. It can be eaten raw in slices as a snack or
dried and ground up into a powder for use as bread flour. Also White
Pines are rich in Vitamin A and C; flour can be made from the Pine
tree’s inner bark. By chewing bark of pine you can eliminate bad breath.
Pines can reduce the pain of skin infections by applying warm pine sap.
Division Angiospermophyta
( Flowering Plants )
General and
Distinctive Features of the Division Angiospermophyta
Explain general and
distinctive features of the division angiospermophyta
Angiosperms
are flowering plants under kingdom Plantae and division
Angiospermophyta. This group of plants is sometimes called
Magnoliophyta. Angiosperms are the most abundant land plants. Like
gymnosperms, angiosperms are seed-producing plants but they are
distinguished from gymnosperms by their characteristic of producing
flowers. These plants produce fruits that contain seeds instead of cones
like it is in gymnosperms. The term angiosperm means a plant that
produces seeds within fruits.
Angiosperms life cycle:The
ovary has ovules that contain mega-sporocyte. Mega-sporophyte has four
haploid megaspores; three megaspores disintegrate and the remaining one
divides by mitotic divisions to produce eight nuclei in an embryo sac.
The three nuclei are organized into the egg whereby one cell is the egg
cell; the two others are egg helpers. Although these three cells look
are similar, only the egg cell continues to develop to an embryo sac.
The embryo sac at this stage is the female gametophyte or
mega-gametophyte.
Pollination and fertilization:The
pollen from the anther is transported to the stigma of a flower. In the
stigma pollen tube emerges. The mature male gametophyte therefore is a
germinated pollen grain, pollen tube and three sperm nuclei. The pollen
tube grows downward toward the ovary through the style and penetrates
the embryo sac. After discharging its contents one of the sperm nuclei
fuses with the egg nucleus and form a zygote, the other sperm fuses with
the polar cell of the ovary, forming the endosperm nucleus. This is
what is known as double fertilization. Fertilization in angiosperms
begins very soon after pollination.
Note: In gymnosperms,
fertilization can occur up to a year after pollination.
Double fertilization:Double
fertilization is a distinctive characteristic of the angiosperms and
results in a polyploid endosperm tissue. In double fertilization each
ovule receives a pollen tube that delivers two sperm cells to the embryo
sac. One sperm fertilizes the egg cell to form the diploid zygote,
while the other sperm fertilizes the central polar cell to form triploid
endosperm. After double fertilization, the ovule develops into a seed
and the ovary into a fruit.
General features of angiosperms
They
bear flowers which are reproductive structures. Fertilization takes
place between male and female flower by pollination that includes insect
pollination, wind pollination and animal pollination.
1. Angiosperms have underground root as well as
aerial shoot system.
2. Angiosperms
have very well-developed conducting tissues. These tissues include the
xylem and the phloem arranged in form of vascular bundles.
3. They have root that helps absorption of water
and minerals from the soil.
4. Most of them have leaves that carry out
photosynthesis, so they are autotrophs.
5. They
have alternation of generation, Sporophyte generation alternate with
gametophyte generation. The sporophyte is the dominant, diploid stage
and is the more visible form of the plant, with the leaves, stems,
roots, and flowers. Gametophyte generation is reduced and it is found
within the ovary and anther.
Distinctive features of angiosperms
1. The most obvious distinguishing feature of
angiosperms is the possession of reproductive structures called flowers.
2. They bear seeds enclosed in a carpel (the fruit).
The seeds are the fertilized ovules.
3. They
have endosperm produced after fertilization and before the zygote
undergo its first division. Endosperm has nourishing function, it
nourishes the embryo.
4. They have double fertilization whereby
each ovule receives a pollen tube that delivers two sperm cells to the
embryo sac. One sperm fertilizes the egg cell to form the diploid
zygote, while the other sperm fertilizes the central polar cell to form
triploid endosperm.
5. Their haploid gametophyte is confined inside
the ovary (female) or anther (male) of the flower, unlike the free-
living gametophytes of most other plants.
6. They have conducting tissues phloem and xylem.
Unlike gymnosperms which have xylem tracheid angiosperms has xylem vessels.
The Classes of the Division
Angiospermophyta and their Distinctive Features
Outline the classes of
the division angiospermophyta and their distinctive features
Division
Angiosperms is divided into two classes which are Monocotyledonae and
Dicotyledonae. These two classes are distinguished from each other by
their morphology and anatomy.
Features of Class
Monocotyledonae
1. Monocots have one cotyledon (or one seed leaf)
2. Monocots have broad leaves with parallel
venation.
3. Monocots have fibrous root systems.
4. The floral parts in monocots occur in threes,
or multiple of three. PMonocots lack cambium secondary growth.
5. Monocots have scattered vascular bundles in
their stems.Typical example of monocot is a maize plant.
Features of Class Dicotyledonae
1. Dicots have two cotyledons (or two seed leaves).
2. Dicots have net venation.
3. Dicots have tap root system
4. Dicots floral parts occur in fours and fives
and multiple of four or five.
5. Dicots have cambium secondary growth.
6. Dicots have vascular bundles arranged into a
ring. A Typical example of dicot is a bean plant.
The Structure of
Representative Plants Under Each Class (Monocotyledonae and Dicotyledonae)
Describe the structure
of representative plants under each class (Monocotyledonae and Dicotyledonae)
Structure
ofMonocotyledonae and Dicotyledonae plants
Advantages and
Disadvantages of Division Angiospermophyta
Explain advantages and
disadvantages of division dngiospermophyta
Advantages of Angiosperms
1. Agriculture.
Agriculture depends on angiosperms. Angiosperms provide human food.
Example; plants belonging to grass family (grains), are the most
important food stocks. They include rice, maize, wheat, barley, millet,
sugar cane and sorghum. Legume provides beans, several varieties of nuts
and soy. Also of potatoes, tomatoes, and peppers, pumpkins, melons and
varieties of vegetables to include cabbage and lettuce. Many fruits
oranges, lemons and grapefruits are angiosperms.
2. Livestock.
Plants belonging to grass family are the world number one feeds of
livestock. Many types of grassland in Africa are either grazed by cattle
or wild animals. Also almost all feeds consumed by human are also used
by domestic animals as food.
3. Wood. Angiosperms
provide different varieties of wood for furniture, paper and building
materials. Carpentry and masonry depends largely on angiosperms for both
soft and hard wood.
4. Textile. Different
varieties of fibers including cotton, flax, and hemp are important raw
materials for textile industry. Cotton is the word first class material
for clothes.
5. Medicine. Many organic drugs are
coming from angiosperm herbs. They are either industrial made or can be
utilized in its raw form. Today it is believed that herbs form the best
medicine when used in their fresh form than when industrial made.
6. Floriculture.
Flowers from angiosperms have great social significance as they are
used in different kinds of ceremony. Roses for instance are the most
sold flowers and they are highly purchased and used in wedding and
burial ceremonies.
7. Forestry. Forestry is the
field of study whose base depends on both angiosperms and gymnosperms.
Many forests form green belts that habit different varieties of plants.
8. Ecology.
Angiosperms provide a wide range of habitats for different species of
organisms. They also serve as primary producers of energy.
9. Climate. Angiosperms are used to modify climate.
Green belts are established in order to absorb carbon and reduce global
warming.
10. Tourism.
Many sites of tourism are plants oriented. Ecotourism for instance
depends largely on different plant species that host different kinds of
land animals.
Disadvantages of Angiosperms
1. Toxins.
Some plants are poisonous when eaten by human and other animals. They
cause death to human and other living organisms. Some cassava varieties
are a good example. They have cyanide acid that inhibits cellular
respiration.
2. Drugs. Some angiosperm varieties
are drugs that can be abused when taken. Examples are marijuana,
cocaine, tobacco and some caffeine varieties.
3. Weeds.
Some angiosperm varieties are bad weeds; they reduce crop yields. Some
weeds are parasites. Example, Cuscuta kilimanjari is parasitic to coffee
plantations.
TOPIC 2: MOVEMENT
Concept of Movement
and Locomotion
The Concept of
Movement and Locomotion
Explain the concept of
movement and locomotion
Movement
refers to change of position and posture. Therefore the change of
position of body parts such as limbs and other body parts.
Locomotion is the
movement or change of position of the whole organism from one place to another.
But normally organisms
have different kinds of movement. Plants show movement but do not show
locomotion.
Since
locomotion involves coordination between nervous muscular and skeletal
system and all these system enable the organism to locomote.
The Importance of
Movement in Animals and Plants
Explain the importance
of movement in animals and plants
Animals and plants
move about to:
1. Find a mate and to reproduce
2. Escape danger
3. Seek and capture food
4. To seek shelter, a suitable habitat/climate
5. To avoid competition for food/water, living
space etc
6. Find water/soil nutrients, and hold leaves to
get maximum sunlight
7. Seek and capture food
8. Obtain support
9. Protect themselves from damage from:
touch/pressure, pain or sudden temperature change
10. Disperse seeds
Movement and
Locomotion Actions
Demonstrate movement
and locomotion actions
Demonstration of
movement and locomotion
Movement action
Locomotion action
Movement of the Human
Body, the Human Skeletal System
The Structures of
Human Skeleton
Describe the
structures of human skeleton
The
contraction and relaxation of muscles cause muscular movement in
vertebrate organisms such as man. The muscles work together with
skeletal system to support or allow movement to occur.BONES, CARTILAGE,
JOINTS AND MUSCLES
The Functions of the
Major Components of the Human Skeleton and their Adaptations
Explain the functions
of the major components of the human skeleton and their adaptations
Major Components of
the Human Skeleton includeBones, Cartilage, Joints and Muscles
Bones
Bones
consist of living cells embedded in a hard substance made mainly: The
bones are attached together at the joints by tough flexible fibers known
as ligaments
Bones are classified
in to long, short, irregular bones and flat.
· Short bones these are short bones, which support
weight allowing for many smaller movements. Example bones on the human feet.
· Long bones
these are strong, hollow and light containing spongy bone at the end.
And spongy bone has open space and holes, which contain red marrow,
which is where red cells are made. Example bones on the legs and arms.
· Flat bones these are bones, which support and
protect body organs, these comprises ribs, breastbone, shoulder bones etc.
· Irregular bones these bones are for support and such
bones are vertebrae also human ear has three tiny irregular bones, which
conduct sound.
Cartilage
Besides
bones, the skeletal system has tissue called cartilage. It’s the strong
flexible tissue that gives shape to some parts of the body
The cartilage keeps
bones from grinding against each other, between vertebrae cartilage disks act
as shock absorbers
Before birth bones are
made mostly of cartilage whose cells absorb calcium after birth to produce
bones
Joints
The human skeleton has
about seventy movable joints.
Pivot Joint:This
is the type of joint, which allows one bone to twist against another
NB. Joint is the point
where two or more bones meet
Pivot joint allows
movement in several directions
Hinge joint is the
joint which allows movement in one direction Example elbow
Functions of Skeleton
include:
1. The human skeleton provides mechanical support
for the body
2. Protection for internal organs e.g. skeleton
of head protects the brain while chest bones protect soft organs such as the
heart
3. Skeleton functions as framework for anchoring
the muscles
4. Skeleton, together with muscles, function to
bring about movement in an organism
Muscles and Movement
The Concept of Muscles
Explain the concept of
muscles
A
muscle is a tissue consisting of cells that have the capacity to
contract and exert a pull. Muscles are made up of specialized tissues,
which are known as contractile tissues. When these tissues contract they
become shorter and tighter, as a result they cause movement. All
muscles are made up of elongated cells called muscle fibers.
Types of Muscles
Mention types of
muscles
There
are three kinds of muscles in the body of a mammal. These muscles are
skeletal muscles (voluntary), smooth (involuntary) muscles and cardiac
muscles.
How Muscles Facilitate
Movement
Demonstrate how
muscles facilitate movement
Muscles are attached
to bones at two points:
· At one point a muscle is usually attached to
an immovable bone and other end to a movable bone.
· Muscles
may be attached directly or indirectly by means of tendons. Tendons are
tough whitish cords of fibrous materials which connect a bone and a
muscle
· Muscles can contract and relax, but not expand
when
muscle contracts it becomes shorter and thicker and hence, exerts a
pulling force on bone to which it is attached at a point of insertion.
· When a muscle relaxes, it lengthens and
becomes thinner
· Most
muscles act in pairs in such a manner that when one member of the pair
contracts the other member relaxes. This means that they never contract
or relax at the same time
· Muscles acting in pairs in this manner
are known as antagonistic muscles. One member of the pair is called
extensor while the other member is the flexor
The
figure below shows how the two muscles of the upper arms that is the
biceps and triceps muscles bringing about the bending and straightening
of the limb.
When
the triceps (extensor) muscle contracts the limb is straightened. The
contraction of the triceps is accompanied by the relaxation of the
biceps (flexor). When the biceps muscle contracts the arm bends.
The Structure of
Muscles
Describe the structure
of muscles
Structure of mucles
Adaptations of
Different Types of Muscles to their Roles
Explain adaptations of
different types of muscles to their roles
Skeletal Muscles
· These are the muscles, which are attached to
bones of the skeleton
· The skeletal muscles contract powerfully and
fatigue quickly
· Their contractions are controlled by the brain
for this reason they are called voluntary muscles
Function of Skeletal Muscles
· Skeletal muscles are concerned with the
movement of the limbs and parts of the skeleton
Smooth Muscles
Smooth (involuntary)
muscles are found on the walls of internal organs such as alimentary canal,
blood vessels and bladder.
· These muscles are made up of cells which taper
at both ends (spindle shaped)
· Smooth muscles contract slowly
· The contraction of the smooth muscle is
involuntary (it is not controlled by the brain)
Function of Smooth Muscles
The
smooth muscles, which are formed in different organs contract and relax
to cause movements of materials through them. Example: peristalsis in
alimentary canal causes movements of the materials through the canal
with the help of smooth muscles.
Cardiac Muscles
This
is the type of muscle, which is found only in the heart. These muscles
are made up of muscle fibers which branch and connect to each other like
a network.
Function
· Contraction of cardiac muscles causes the
heart to keep on pumping (i.e. heart beat)
Causes, Effects and
Preventive Measures of Muscles Cramps
Explain causes effects
and preventive measures of m cramps
A
muscle cramp is an involuntary and forcibly contracted muscle that does
not relax. The cramp may involve a part of muscle, the entire muscle or
several muscles that usually act together. Any of the muscles that are
not at our voluntary control can cramp.
Sometimes
it occurs when the body lacks salt especially for those people who work
hard in hot weather they sweat a lot and get painful cramps in their
legs, arms or stomach.
Causes Muscle Cramps
There are basically
two major causes of muscle cramps that are:
· Lack of water or salt in the body
· Lack of oxygen in the muscles (inadequate
oxygenation of muscles)
Prevention of Muscle
Crampa
· Cramps from poor breathing (lack of oxygen)
can be improved by rapid breathing as well as stretching the muscles
· A
muscle cramp from lack of water or salt can be treated by stretching
the muscles and drinking many glasses of water, which contain salt so as
to replace the amount of salt lost in the body
Treatment of Muscle
Cramps
Applying
a soft massage on the cramped muscle, stretching the muscle and
applying oil ointment on the affected area, can treat a muscle cramp.
Movement in Plants
The Concept of
Movement in Plants (Movement of Curvature)
Explain the concept of
movement in plants (movement of curvature)
Generally
plants do not show locomotion (movement of the entire organism).
However, movement of individual plant organs is possible and modified by
sensitivity of the plant to external stimuli.
Plant movements in
response to internal stimuli are known as spontaneous movement.
Examples of these movements are metabolic conditions, disease
conditions, vex ages and parental influence Those movements shown by
plants in response to external stimuli are known as induced or irritablemovements.
Types of Movement
Exhibited by Plants
Mention types of
movement exhibited by plants
Normally there are two
types of plant movements, which are:
1. Spontaneous movement
2. Induced (irritable) movement
Spontaneous Movement
is plant movement in response to internal stimuli. Example of these
movements are metabolic conditions, disease conditions, vex ages and
parental influences
Induced or Irritable Movement
is the type of plant movement shown by plants in response to external
stimuli. Light, temperature, gravity, touch, water and chemical
substances are examples of induced movement.
Induced movements
include nastic movement, tactic movement and tropic movement.
A summary of the types
of movements shown by plants in response to stimuli.
STIMULI
· Light
· Chemicals
· Water
· Temperature
· Contact
· Gravity
· Gravitactic or Gravitaxis
Tropic Movements in Plants
Tropic
movements are the growth movements shown by a fixed part of a
stationary plant towards or away from a stimulus coming from one
direction. Tropic movements are also known as tropism movements.
Tropic
(tropism) is growth movements, which take place at a very slow pace.
The growth movement is caused by an increased or decreased rate of
growth on the side of the organ, which is under the influence of the
stimulus, with respect to the opposite side. This results in growth in
curvature.
There are various
types of tropic movements, these types are:
· Phototropism or phototropic which is a growth
movement shown by part of a fixed plant in response to light
· Hydrotropism (Hydrotropic) which is growth
movement in a response to water
· Thigmotropism (Thigmotropic) which is the
growth movement in response to touch
· Chemotropism (Chemotropic) which is a growth
movement made by plants towards chemicals
· Thermotropism (Thermotropic), a growth
movement shown in plants in response to heat.
Experiments to
Investigate Movement in Plants
Carry out experiments
to investigate movement in plants
An experiment to
investigate movement in plants
TOPIC 3: COORDINATION
In
this topic you will learn about concept of coordination, nervous
coordination inhumans, sense organs, drugs and drug abuse in relation to
nervous coordination, andcoordination in plants.
Concept of
Coordination.
The Concept of
Coordination in Organisms
Explain the concept of
coordination in organisms
Coordination
is the working together of the various organs of an organism in a
systematic manner so as to produce a proper response to the stimuli.
Without coordination the body becomes disorderly and it may fail to
function properly.
The Ways in Which
Coordination is Brought About
Outline the ways in
which coordination is brought about
The
coordination in simple multicellular animals takes place through
nervous systemonly. The control and coordination in higher animals
called vertebrates (including humanbeings) takes place through nervous
system as well as hormonal system called endocrinesystem. Coordination
in plants is under the control of hormones.
All
the living organisms (plants and animals) respond and react to changes
in the environment around them. The changes in the environment to which
the organisms respond and react are called stimuli (singular: stimulus).
The living organisms show response to stimuli such as light, heat,
cold, sound, smell, taste, touch, pressure, pain,water, and force of
gravity, etc. The ability to perceive, interpret and respond to stimuli
is called irritability or sensitivity.
There
are two types of stimuli: external and internal. External stimuli are
associated with the surrounding environment such as wind temperature,
light, pressure, touch, water and gravity. Internal stimuli occur within
the organism, for example, a decrease or an increase in the amount of
water and glucose in the blood.
When
an organism detects a stimulus, it initiates a response. A response is a
behavioural,physiological or muscular activity initiated by a stimulus.
For example, if a man touches a very hot utensil accidentally, he
quickly pulls his hand away from the hot utensil. Here,heat is the
stimulus and the man reacts (responds) by moving his hand away from the
hot utensil. Similarly, when the sun is bright, we close our eyes. In
this case, light is the stimulus and we react by closing our eyes.
Likewise, when the amount of water in the blood drops, the pituitary
gland secretes an anti-diuretic hormone (ADH) which stimulates the
reabsorption of water in the kidneys.
Multicellular
organisms detect stimuli through sense organs called receptors. A
receptor is a sense organ (e.g. eye) or sensory nerve ending (e.g. in
the skin or internal organ) which receives stimuli and sets nervous
impulses. Impulses are electrical transmissions or chemical stimuli that
are sent from the receptor to the coordinating system in the organism.
The organs that respond to the stimuli are called effectors. A
coordinator is an organ (e.g. the brain and spinal cord) that receives
messages from the receptors,translates them and sends the information
back to an effector for action. An effector is a muscle or gland which
receives impulses from nerves, brain or spinal cord and responds to
them. Response is the end-action, such as a muscle contracting to cause
the movement of the arm. The diagram below illustrates the five
components of coordination in mammals.
Nervous Coordination in
Human , Neurons
The Structure of Motor
Sensory and Relay Neurons
Describe the structure
of motor sensory and relay neurons
Neurones
Neurones
are nerve cells. They carry information as tiny electrical signals. A
neuroneconsists of a cell body (with a nucleus and cytoplasm), dendrites
that carry electricalimpulses to the cell, and a long axon that carries
the impulses away from the cell. Theaxon of one neurone and the
dendrites of the next neurone do not actually touch eachother. The gap
between neurones is called the synapse
Structure and
functions of neurones
The
diagram below shows a typical neurone: in this case, a motor neurone.
It has tinybranches at each end (dendrites) and a long fibre (axon) that
carries the signals or nervousimpulses. The axon is surrounded by a
fatty layer known as the myelin sheath. Thishelps to protect the neurone
and allow impulses to travel faster. The sheath is produces bySchawnn
cells. The myelin sheath has nodes (Nodes of Ranvier) that speed
uptransmission of nervous impulses. The cell body consists of cytoplasm
enclosing thenucleus. There are also other organelles in the cytoplasm
such as mitochondria thatsupply energy to for metabolic functions.
Synapses
Where
two neurones meet, there is a tiny gap called a synapse. Signals cross
this gapusing chemicals (neurotransmitters) released by a neurone. When
the chemical diffusesacross the gap it makes the next neurone transmit
an electrical signal. The transmission ofnervous impulses across
synapses occurs thus:
1. An electrical impulse travels along an axon.
2. This triggers the nerve-ending of a neuron to
release chemical messengers calledneurotransmitters.
3. These chemicals diffuse across the synapse
(the gap) and bind with receptormolecules on the membrane of the next neuron.
4. The
receptor molecules on the second neuron bind only to the specific
chemicalsreleased from the first neuron. This stimulates the second
neuron to transmit theelectrical impulse.
Types of neurones
There
are three types of neurones namely motor neurone, sensory neurone and
relay(or intermediate) neurone. Each of these neurones has a different
structure and performsdifferent functions.
Motor neurone
A
motor neurone is a nerve cell that transmits impulses from the central
nervous system(CNS) to the effector organs such as muscles or glands
where response is made. The cellbody of a motor neurone is at one end of
the neurone and lies entirely within the centralnervous system (see the
diagram above).
Sensory neurone
A
sensory neurone is a nerve cell that transmits impulses from the
receptors to the CNS.Sensory neurones have their cell bodies off the
axon and outside the central nervoussystem.
Relay (intermediate or
inter) neurone
A
relay neurone conveys messages between neurones in the CNS. Relay
neurones arelocated in the CNS between the sensory and the motor
neurones.
Central Nervous System
(CNS)
The Meaning of Central
Nervous System
Give the meaning of
central nervous system
The
CNS is the part of the nervous system consisting of the brain and
spinal cord. Itcoordinates all the neural functions. The chart below
shows subdivisions of the nervoussystem.
The brain
The
human brain is a specialized organ that is ultimately responsible for
all thought andmovement that the body produces. This allows humans to
successfully interact with theirenvironment, by communicating with
others and interacting with inanimate objects neartheir surroundings. If
the brain is not functioning properly, the ability to move,
generateaccurate sensory information or speak and understand language
can be damaged as well.
The
brain has many different parts. Each part has a unique function that
allows humansobserve and interact with their environment effectively.
The following are parts of thehuman brain and their functions:
Cerebrum
The
cerebrum is the largest portion of the brain, and contains tools which
are responsiblefor most of the brain’s function. It is divided into four
sections: the temporal lobe, theoccipital lobe, parietal lobe and
frontal lobe.
Parietal
Lobe: Located in the cerebral hemisphere, this lobe focuses on
comprehension.Visual functions, language, reading, internal stimuli,
tactile sensation and sensorycomprehension are monitored here.
Temporal
Lobe: The temporal lobe controls visual and auditory memories. It
includesareas that help manage some speech and hearing capabilities,
behavioural elements, andlanguage. It is located in the cerebral
hemisphere.
Occipital Lobe: the
occipital lobe is located in the cerebral hemisphere in the back of thehead. It
helps to control vision.
Cerebellum
This
is commonly referred to as “the little brain‖. The cerebellum controls
essential bodyfunctions such as balance, posture and coordination,
allowing humans to move properlyand maintain their posture.
Limbic system
The
limbic system contains glands which help relay emotions. Many hormonal
responsesthat the body generates are initiated in this area. The limbic
system includes theamygdala, hippocampus, hypothalamus and thalamus.
Amygdala: The amygdala
helps the body responds to emotions, memories and fear.
Hippocampus:
This portion of the brain is used for learning memory,
specificallyconverting temporary memories into permanent memories which
can be stored within thebrain.
Hypothalamus:
The hypothalamus region of the brain controls mood, thirst, hunger
andtemperature. It also contains glands which control the hormonal
processes throughout thebody.
Thalamus:
The thalamus is located in the centre of the brain. It helps to control
theattention span, sensing pain and monitors input that moves in and
out of the brain to keeptrack of the sensations the body is feeling.
Brain stem
All
basic life functions originate in the brain stem, including heartbeat,
blood pressureand breathing. In humans, this area contains the medulla,
midbrain and pons.
Midbrain: This part of
the brain helps regulate body movement, vision and hearing.
Pons:
The pons interprets information that is used in sensory analysis or
motor control.The pons also creates the level of consciousness necessary
for sleep.
Medulla:
The medulla or medulla oblongata is an essential portion of the brain
stemwhich maintains vital body functions such as the heart rate and
breathing.
The diagram below
shows and summarizes the basic functions of different parts of thebrain.
The Components of the
Central Nervous System and their Functions
Identify the
components of the central nervous system and their functions
The table below
summarizes the structure and functions of the major components of thebrain.
The Structure of the
Spinal Cord and Brain
Describe the structure
of the spinal cord and brain
Spinal cord
The
spinal cord functions primarily in the transmission of neural signals
between thebrain and the rest of the body but also contains neural
circuits that can independentlycontrol numerous reflexes and central
pattern generators. It carries out two mainfunctions:
1. It
connects a large part of the peripheral nervous system to the brain.
Information(nerve impulses) reaching the spinal cord through sensory
neurons is transmitted upinto the brain. Signals arising in the motor
areas of the brain travel back down thecord and leave in the motor
neurones.
2. The spinal cord also acts as a minor
coordinating centre responsible for some simplereflexes like the withdrawal
reflex.
The intermediate
neurones carrying impulses to and from specific receptors and effectorsare grouped
together in spinal tracts.
The diagram shows
various sections of the spinal cord and the functions of each section.
Peripheral Nervous System
(PNS)
The Meaning of
Peripheral Nervous System
Give the meaning of
peripheral Nervous System
The
peripheral nervous system is made up of a network of nerves linking
various parts ofthe body to the brain and spinal cord. It includes the
cranial nerves, spinal nerves andtheir roots and branches, peripheral
nerves, and neuromuscular junctions.
The
peripheral nervous system (PNS) has two components: the somatic nervous
systemand the autonomic nervous system. The PNS consists of all of the
nerves that lie outsidethe brain and spinal cord.
The Components of the
Peripheral Nervous System and Their Functions
Identify the components
of the peripheral nervous system and their functions
The
somatic nervous system is made up of nerves that connect to voluntary
skeletalmuscles and to sensory receptors. It is composed of afferent
nerves that carryinformation to the central nervous system (spinal cord)
and efferent nerves that carryneural impulses away from the central
nervous system. This system is responsible for theinvoluntary control of
the skeletal muscles, bones and sense organs.
The autonomic nervous
system is further subdivided into sympathetic andparasympathetic nervous
system.
1. The
sympathetic nervous system activates the ‗fight or flight’ response
under suddenor stressful circumstances, for instances by raising the
heart rate and dilating thepupils.
2. The parasympathetic nervous
system helps the body return to normal activity afteran emergency, which
conserve energy and replenishes the system.
Together,
these two systems regulate homeostasis within the body – one preparing
thebody for action, and the other repairing the body afterward.
Reflex Action
The Meaning of Reflex
Action
Give the meaning of
reflex action
When
a receptor is stimulated, it sends a signal to the central nervous
system, where thebrain co-ordinates the response. But sometimes a very
quick response is needed, one thatdoes not need the involvement of the
brain. This is a reflex action.
The
reflex action is a rapid, involuntary response to a certain stimulus.
The route that isfollowed by impulses during a reflex action is called a
reflex arc.
Reflex
actions are rapid and happen without us thinking. For example, you
would pullyour hand away from a hot flame without thinking about it. The
diagram below shows asimplified reflex arc.
This is what happens:
1. receptor detects a stimulus – change in the
environment
2. sensory neurone sends signal to relay neurone
3. motor neurone sends signal to effector
4. effector produces a response
The above process
appears to be a long one but, in reality, the process takes a very shorttime.
It happens within seconds.
The
way the iris in our eye adjusts the size of the pupil in response to
bright or dim lightis also a reflex action. It happens without our
thinking and beyond our control.
The Neuronic Path of a
Reflex Action
Describe the neuronic
path of a reflex action
A reflex action can
either be simple or conditioned reflex.
Simple reflex action
An
example of a simple reflex found in humans is the pupil reflex, where
the pupil of theeye gets larger in dim light and smaller in bright
light.The eye needs to control the amount of light entering it in
different light conditions. Indim conditions, more light is allowed to
enter so that a clear image can be formed on theretina. In bright
conditions, less light is allowed to enter so that the retina is not
damaged.
Conditioned reflex
action
A conditioned reflex
is some action or feeling that is learned in response to a specificsituation or
stimulus.
A
Russian scientist called Pavlov trained dogs to expect food whenever he
rang a bell.The dogs eventually produced saliva when they heard the
bell ring. The dog salivatesnaturally when given food. Pavlov rung a
bell every time the dogs were to be given food.After much repetition the
dogs salivated when they heard the bell ringing, even whenthere was no
food. This is an example of a conditioned reflex.
The
dogs were conditioned to salivate when the bell rang. A ringing bell
does notnormally cause salivation in dogs. However, when the ringing
bell becomes a secondarystimulus, it does cause salivation, even though
the dog will not be able to eat the bell asfood.
This
is now called a conditioned reflex. In a conditioned reflex the final
response(salivation) has no direct connection with the stimulus (ringing
bell).
vAnother
example of a conditioned (learned) reflex is when the driver comes
across ahurdle on the road such as a ditch or a pedestrian. In such
circumstances, the first thingthe driver will do is to move his leg
towards the brake pedal to apply the brakes. He haslearned to do this
action for so long that he finds himself applying the brake in any
ofsuch circumstances.
The Difference between
Simple Reflex and Conditioned Reflex Action
Distinguish simple
reflex from conditioned reflex action
Differences between
conditioned reflex action and simple reflex action
|
Conditioned reflex |
Simple reflex |
|
|
1 |
It involves more than one stimuli |
Requires only one stimulus |
|
2 |
Involves the brain |
Mostly involve the spinal cord |
|
3 |
It is an immediate action (no time to learn) |
It is an immediate action (no time to learn) |
|
4 |
It is acquired in one‘s life |
It is inborn |
Modifying a reflex
response
In
some circumstances the brain can modify a reflex response. It does this
by sending animpulse along a motor neuron of the reflex arc. This
enables us, for example, to hold ahot dinner plate when normally we
would drop it.
Sense Organs
The Meaning of a Sense
Organ
Explain the meaning of
a sense organ
Sense organs are
organs of the body that detect and respond to changes in theenvironment
(stimuli) so as to survive.
Types of Sense Organs
and Their Relative Position
Identify types of
Sense organs and their relative position
There
are five sense organs in our body: eyes,ears, nose, tongue and skin. We
receive a variety of information from the environmentaround us through
the sense organs. The sense organs contain receptors. A receptor is
acell (or a group of cells) in a sense organ which is sensitive to a
particular type ofstimulus (or a particular type of change in the
environment) such as light, sound, smell,taste, heat, pressure, etc. The
different sense organs contain receptors for detectingdifferent
stimuli.
The
eyes have light receptors (which can detect light), ears have sound
receptors (whichcan detect sound), nose has smell receptors (which can
detect smell), tongue has tastereceptors (which can detect taste)
whereas skin has receptors for detecting touch,pressure, heat (or cold)
and pain, etc.
The Structure of Each
Sense Organ
Describe the structure
of each sense organ
The human eye
The
eye is the organ for vision. The eye is one of the most complex parts
of the body.The different parts of the eye allow the eye to take in
light and perceive objects around usin the proper colour, detail and
depth. This allows people to make more informeddecisions about their
environment. If a portion of the eye becomes damaged, you may notbe able
to see effectively. You may even lose your vision completely.Parts of
the eye and their functionsThere are several physical and chemical
elements that make up the eye. The table belowshows different parts of
the human eye and their functions.Eye part Description and
function(s)Cornea The cornea is the outer, transparent covering of the
eye. This layerprotects the eye from elements that could cause damage to
the innerparts of the eye. The cornea also helps to focus light on the
retina at theback of the eye.Sclera The sclera is commonly referred to
as the “white” of the eye. It protectsthe eye and maintains the shape of
the eye ball.Pupil The pupil appears as a black dot in the middle of
the eye. This blackarea is actually a hole that takes in light to enable
the eye focus on theobjects in front of it. The pupil, thus, controls
the amount of light thatenters the eye.Iris The iris contains the
pigment which gives the eye its colour. It has radialInternal structure
Parts of the eye and
their functions
There
are several physical and chemical elements that make up the eye. The
table belowshows different parts of the human eye and their functions.
|
Eye part |
Description and function(s) |
|
Cornea |
The |
|
Sclera |
The sclera is commonly referred to as the “white” of the
eye. It protects the eye and maintains the shape of the eye ball. |
|
Pupil |
The |
|
Iris |
The |
|
Conjunctiva |
This |
|
Lacrimal glands |
These |
|
Lens |
This |
|
Retina |
Retina |
|
Ciliary body |
Ciliary body, also called ciliary muscles, |
|
Suspensory ligaments |
The |
|
Choroid |
The |
|
Vitreous humour |
The |
|
Aqueous Humor |
The |
|
Optic nerve |
Optic |
|
Blind spot |
It |
|
Fovea |
The |
Adaptations of the eye to its functions
The eye is adapted to
its functions by possessing the following features:
1. Conjunctiva, cornea and lens are transparent
to allow light to pass through them.
2. Sclerotic layer is made up of (collagen)
fibres; it maintains shape of eyeball/protectsthe eye from mechanical damage.
3. Cornea is transparent and curved thus refracts
light rays and allows light to passthrough.
4. Choroid (a layer of a tissue) has black or
dark pigments that prevent internalreflections of light in the eye.
5. The
eye contains blood vessels in the choroids layer that supply oxygen and
nutrientsto the eye, giving the eye energy to perform its function, and
removes the metabolicwastes from the eye.
6. Retina is made of photoreceptors known as rods
and cones, which trap light rays toenable the eye to do its function of vision.
7. Yellow spot (fovea) has the highest
concentration of cones for accurate and sharp,central vision.
8. Optic nerve has sensory neurones for transmission
of nerve impulses to the brain (forinterpretation).
9. Lens
is biconvex and made up of elastic, transparent material which adjusts
to focusfar or near objects and allows light rays to pass through.
10. Suspensory ligaments are fibrous to hold the
lens in place.
11. .
The ciliary body contains ciliary muscles which are contractile to for
controlling thecurvature and hence focal length of the lens. It also
contains glands that secrete theaqueous and vitreous humours.
12. The iris is opaque and contractile for controlling
the amount of light entering the eye(by adjusting the size of the pupil).
13. Ocular muscles coordinate eye movement so that
both eyes can follow a movingobject together.
14. The eyelid covers an eye and prevents it from
mechanical damage and invasion byforeign bodies.
15. Eye lashes help to prevent dust and small
insects or particles from entering the eyeby trapping them on their hairs.
16. The
presence of aqueous and vitreous humours helps the eye to bend light
raystoward retina to process the signal and send impulse to the brain.
The Functions of Sense
Organs and their Adaptive Features
Explain the functions
of sense organs and their adaptive features
Adaptations of the eye to its functions
The eye is adapted to
its functions by possessing the following features:
1. Conjunctiva, cornea and lens are transparent
to allow light to pass through them.
2. Sclerotic layer is made up of (collagen)
fibres; it maintains shape of eyeball/protectsthe eye from mechanical damage.
3. Cornea is transparent and curved thus refracts
light rays and allows light to passthrough.
4. Choroid (a layer of a tissue) has black or
dark pigments that prevent internalreflections of light in the eye.
5. The
eye contains blood vessels in the choroids layer that supply oxygen and
nutrientsto the eye, giving the eye energy to perform its function, and
removes the metabolicwastes from the eye.
6. Retina is made of photoreceptors known as rods
and cones, which trap light rays toenable the eye to do its function of vision.
7. Yellow spot (fovea) has the highest
concentration of cones for accurate and sharp,central vision.
8. Optic nerve has sensory neurones for
transmission of nerve impulses to the brain (forinterpretation).
9. Lens
is biconvex and made up of elastic, transparent material which adjusts
to focusfar or near objects and allows light rays to pass through.
10. Suspensory ligaments are fibrous to hold the
lens in place.
11. .
The ciliary body contains ciliary muscles which are contractile to for
controlling thecurvature and hence focal length of the lens. It also
contains glands that secrete theaqueous and vitreous humours.
12. The iris is opaque and contractile for
controlling the amount of light entering the eye(by adjusting the size of the
pupil).
13. Ocular muscles coordinate eye movement so that
both eyes can follow a movingobject together.
14. The eyelid covers an eye and prevents it from
mechanical damage and invasion byforeign bodies.
15. Eye lashes help to prevent dust and small
insects or particles from entering the eyeby trapping them on their hairs.
16. The
presence of aqueous and vitreous humours helps the eye to bend light
raystoward retina to process the signal and send impulse to the brain.
The human ear
The
ear is the organ of hearing and maintaining balance and posture. The
outer earprotrudes away from the head and is shaped like a cup to direct
sound waves toward thetympanic membrane, which transmits vibrations to
the inner ear through a series of smallbones (ossicles) in the middle
ear called the malleus, incus and stapes. The inner ear, orcochlea, is a
spiral-shaped chamber covered internally by nerve fibres that react to
thevibrations and transmit impulses to the brain via the auditory nerve.
The brain combinesthe input of our two ears to determine the direction
and distance of sounds.
The
inner ear has a vestibular system formed by three semicircular canals
that areapproximately at right angles to each other and which are
responsible for the sense ofbalance and spatial orientation. The inner
ear has chambers filled with a viscous fluid andsmall particles
(otoliths) containing calcium carbonate. The movement of these
particlesover small hair cells in the inner ear sends signals to the
brain that are interpreted asmotion and acceleration. The figure below
shows the internal structure of themammalian ear.
Adaptations of the
mammalian ear to its functions
The ear is adapted to
its functions by possessing the following features:
1. The outer ear (pinna) is a flap of tissue
which collects sound waves and directs theminto the inner ear via the auditory
canal.
2. The
lining of auditory canal contains wax-secreting cells which produce
wax. Thewax in the canal traps dust particles and other foreign bodies
and hence protects theinner delicate parts of an ear from mechanical
damage or microbial infections.
3. The ear drum is thin and
membranous, a fact that enables it to vibrate when soundwaves hit it
before converting the waves into vibrations and passing them on to
theear ossicles in the middle ear.
4. The ear ossicles (malleus,
incus and stapes) act as a lever system which can moveforward and
backward to amplify and transmit vibrations to the oval window.
5. The
Eustachian tube is hollow, a fact which allows air in and out of the
middle ear toequalize the pressure between the inside and outside of the
ear drum—whichimproves the drum‘s ability to vibrate
6. The
cochlea is coiled to increase the surface area for sound reception. It
also cariesauditory nerves which transmit sound impulses to the brain
for interpretation.pinnaear drumskull bonesemi-circular canalsauditory
canaleustachian tuberound windowcochleaauditory nerveInternal structure
of the human earoval window
7. The presence of fluid-filled
vestibular apparatus (semi-circular canals, sacculus, andutriculus) in
the inner ear facilitates balancing of sound when the fluid is
displaced.
The tongue
The
tongue is an organ responsible for taste. It is the primary organ of
taste (gustation), asmuch of its upper surface is covered in taste buds.
The tongue’s upper surface is alsocovered with numerous lingual
papillae. The tongue is sensitive and kept moist by saliva,and is richly
supplied with nerves and blood vessels.
The
receptors for taste, called taste buds, are situated chiefly in the
tongue, but they arealso located in the roof of the mouth near the
pharynx. They are able to detect four basictastes: salty, sweet, bitter,
and sour.
Generally,
the taste buds close to the tip of the tongue are sensitive to sweet
and saltytastes, whereas those in the back of the tongue are sensitive
to bitter tastes. The taste budsin the sides of the tongue are sensitive
to sour tastes. At the base of each taste bud there isa nerve that
sends the sensations to the brain. The sense of taste functions in
coordinationwith the sense of smell.
The
number of taste buds varies substantially from individual to
individual, but greaternumbers increase sensitivity. Women, in general,
have a greater number of taste budsthan men. As in the case of colour
blindness, some people are insensitive to some tastes.
Adaptation of the
tongue to its functions (as a sense organ)
The tongue is adapted
to its functions by possessing the following features:
1. The tongue has taste buds which help it to
respond the stimuli such as sweet, bitter,sour and salty.
2. At the base of each taste bud there is a nerve
that sends the sensations to the brain.
The human nose
The
nose is the organ responsible for the sense of smell. The cavity of the
nose is linedwith mucous membranes that have smell receptors connected
to the olfactory nerve. Thesmells themselves consist of vapours of
various substances. The smell receptors interactwith the molecules of
these vapours and transmit the sensations to the brain. The
smellreceptors are sensitive to seven types of sensations that can be
characterized as camphor,musk, flower, mint, ether, acrid, or putrid.
The sense of smell is sometimes temporarilylost when a person has a
cold. Dogs have a sense of smell that is many times moresensitive than
man’s.
When
we want to ―smell‖ food we draw air
high up into the nasal cavity where
thechemicals come into contact with hairs on the sensory cells.
Different chemicalsstimulate different sensory cells and nervous
impulses are set up which pass along
theverves to the brain to be
interpreted.
When our nose is
blocked with cold, our food may become ―tasteless‖ because we nolonger smell it.
Adaptations of the
nose to its functions
The nose is adapted to
its functions by possessing the following features:
1. There
are olfactory nerves, which carry impulse from the nose to the
olfactory lobesof the brain for interpretation.The human nose
2. Presence of mucus-secreting cells, which
produce mucus that keep the surface of thenose moist.
3. Presence
of hairs in the nose helps the nose to trap dust particles and other
foreignbodies. When the mucus is blown out from the nose, it carries the
dust and otherforeign bodies with it, thus preventing the olfactory
organs from damage.
The human skin
The
skin is the outer covering of the body. In humans, it is the largest
organ of theintegumentary system. The skin has multiple layers of
ectodermal tissue and guards theunderlying muscles, bones, ligaments and
internal organs. It protects us from microbesand the elements; helps
regulate body temperature; and permits the sensations of touch,heat, and
cold.
The skin has three
layers:
1. The epidermis, the outermost layer of skin, provides a
waterproof barrier andcreates our skin tone
2. The dermis, beneath the epidermis, contains tough
connective tissue, hairfollicles, and sweat glands
3. The deeper subcutaneous layer (hypodermis) is made of fat and connectivetissue.
The
skin‘s colour is produced by special cells called melanocytes, which
produce thepigment melanin. Melanocytes are located in the epidermis.
The
skin contains sensory nerve endings which are receptors. They are
sensitive to pain,pressure, touch, heat and coldness. When the nerve
endings are stimulated they set upnervous impulses which are sent to the
spinal cord or brain to be interpreted.
Functions of skin
1. Regulation:
The skin plays an important role in regulation of body temperature inan
organism thus helping to keep the body temperature constant
(endothermic).
2. The skin manufactures vitamin D through
exposure
to sunlight. Ergosterol in thefatty layer of the skin converts into
vitamin D under the influence of sunlight.
3. The skin produces melanin that protects the
body from ultra violet radiationswhich can cause skin cancer.
4. The skin acts as sensory organ due to the
presence of various nerve endings.
5. Protection: It prevents micro-organism and
other foreign materials from enteringthe body.
6. Excretion: Sweat glands produce sweat, which
gets rid of excess heat, water, salts,some carbon dioxide and urea.
7. Storage: Fat is a food store in the dermis.
Adaptations of the
skin to its functions (as a sense organ)
The human skin is
adapted to its sensory functions by having the following features:
1. It
has the hair erector muscle which controls whether the hair stands
erect or liesdown depending on the temperature of the surrounding.
2. It is supplied with nerves which convey
impulses to the CNS to be interpreted.
3. Presence
of blood vessels (in the dermis) which dilate when the body temperature
ishigh to facilitate heat loss by radiation and constrict when the
temperature is low toreduce heat loss. The blood vessels also supply
nutrients and oxygen to the skin andremove excretory products.
4. The
skin has sweat glands which produce sweat to help cool the body. During
a hotday, the glands produce sweat (through sweat pores). Evaporation
of the sweat usesthe body heat and hence helps to cool down the body.
Drugs and Drug Abuse in
Relation to Nervous Coordination
The Meaning of Drugs
and Drug Abuse, in Relation to Nervous Coordination
Explain the meaning of
drugs and drug abuse, in relation to nervous coordination
Drugs
A
drug is any chemical substance, natural or synthetic, that has known
physiologicaleffects on humans or other animals. Foods are generally
excluded from this definition, inspite of their physiological effects on
animal species.
Most
drugs, both useful and harmful, may affect the body (especially the
brain), byaltering the nerve cells’ natural reaction to these chemicals,
or by mimicking the body’snormal compounds.
Some
drugs slow down the passage of stimuli by affecting nerve cell
membranes, andothers act like neurotransmitters, perhaps passing
stronger or longer-lasting impulses. Assuch they may alter the way
sensory information is processed, or affect the thinkingprocess.
Stimulants
are drugs which speed up the action of the brain e.g. caffeine, found
in tea andcoffee. Sedatives are drugs which slow down the action of the
brain e.g. alcohol. Evenone alcoholic drink will have some effect on the
brain.
Proper Ways of
Handling and Using Drugs
Outline proper ways of
handling and using drugs
Proper use and
handling of drugs
When using and
handling drugs the following precautions must be observed:
1. Avoid taking any drug without diagnosing the
disease and prescription by the doctor.
2. Always stay away from peer pressures and drug
addicts to avoid copying their badhabits.
3. Keep
yourself busy with a number of activities such as sports and games,
readingbooks, etc. Remember ‗an idle mind is the devil‘s workshop‘!
4. Report any case of drug abuse or trafficking
to concerned authorities.
5. Form a counselling club to advise people
especially youths on how to keep off fromdrugs.
6. If one feels addicted, s/he should seek advice
from health officials.
7. Never take a dose more or less that what has
been prescribed by the doctor.
8. Complete
the prescribed dose even after you start feeling well or after the
symptomsof the disease has disappeared.9. Keep all drugs out of reach of
children and drug addicts.
Drug addiction
Drug
addiction refers to the compulsive and repeated use of increasing
amounts of drugswith the appearance of withdrawal symptoms when drug use
ceases. While drug use oftenbegins as a way to seek recreation, the
addictive properties of the drug make an addictcrave for it permanently.
This compulsion is uncontrollable and may interfere with aperson‘s
everyday life. Even when the effects of drugs are damaging to a person‘s
bodyand relationships with friends, family members and co-workers, the
constant need for adrug often overcomes any rational thinking.
The
human body has its own ability to produce some chemicals for its
properfunctioning. The continued use of the drug suppresses the body‘s
ability to produce thesechemicals or diminishes its production because
these chemical are replaced by the drug.The body thus uses the drug as a
substitute for its own natural chemicals. Since thesechemicals are no
longer produced, the body perceives that it needs the drug for
itsfunctioning. Therefore, a person craves for the drug so much that
s/he feels cannot livewithout taking it. At this level the drug abuser
becomes addicted to the drug. This iscalled drug addiction.
Causes and Effects of
Drug Addiction
Explain causes and
effects of drug addiction
Like
many mental health disorders, several causes may contribute to
development of drugaddiction and dependence. Some of the causes of drug
abuse and addiction include thefollowing:
1. Some people take drugs to avoid physical or
emotional pain, discomfort, stress,boredom, anxiety and depression.
2. Some people also take drugs as a way to forget
problems and life hardships theyexperience in life.
3. Recreation: Drug users believe that taking
drugs make them ‗feel better‘ and lively.
4. Peer
pressure leads people to drug so as to create a sense of belonging and
fitting inthe peer group. It‘s often said that teens use drugs when
their friends do. Using drugsallows these young people to fit in with
their peers and blend in with the crowd
5. . Desire for a new
experience and arousal: Some people just take drugs as an‗experiment‘ to
find out the experience the drug users feel, but badly end upbecoming
drug addicts.
6. Lack of life and social skills, for example
drug
resistance skills that would help aperson learn how to say no or avoid
bad influence. People who are easy to copyhabits from others,
irrespective of the outcome of the given habit, can easily get intodrug
use.
Effects of drug abuse
and addiction
Effects of drug abuse
and addiction
Many
illegal chemicals have extreme effects on the function of the brain,
e.g. some drugscause hallucinations – objects around you may change
colour, shape and size, or you maysee and experience things that are not
there at all. Such experiences may cause fear,depression, and mental
disorders. Mostly, these substances alter one’s perception ofreality.
Drugs
produce a variety of short-term effects, but the most common ones
includeincreased heart rate, high blood pressure, dizziness, tremors,
mood changes and paranoia.In high dosages, the risk for more dangerous
effects increases, and the potential for heartattack, stroke,
respiratory failure and coma increases. The various effects of drug
abuseinclude the following:
1. Drugs
confuse the mental faculties so that many drug users die in accidents,
oroverdose on the chemicals. Drugs can also induce them do dangerous
activities suchas unsafe sex or reckless driving.
2. Many drugs induce a feeling of dependency
(addiction) and are linked with criminalactivity.
3. Solvent abuse (sniffing glue, lighter fuel,
etc.) – on which one can easily overdose -can cause death by heart failure.
4. Other
substances can incidentally affect the body’s “thermostat” – located in
thehypothalamus (refer to a topic on homeostasis and osmoregulation)
and cause death,following disruption of the body’s temperature control
and regulation of the body’swater content. Even “legal” chemicals, such
as alcohol (a “social” drug!), haveadverse effects on the body.
5. They can lead to aggressiveness, crime,
violence and divorce.
6. Sharing
of needles used to inject drugs into the bloodstream cause HIV
infections andhepatitis among the addicts. Likewise, because drugs
impair one‘s judgement, it canlead to unprotected sex and hence become
the cause of contracting other sexuallytransmitted diseases like
syphilis, gonorrhoea, chlamydia and herpes.
7. Drugs are very
expensive to purchase. Therefore, the addicts spend much of theirmoney
on drugs at the expense of other family needs.
8. Many drug addicts
are weak and so they cannot participate in in-come
generatingactivities. This leads to poverty, a fact which can lead to
failure to meet one‘s basicneeds.
9. Drug addiction among women can
lead to birth defects which include giving birth tosmall or premature
babies or cause the baby to have withdrawal symptoms, birthdefects or
learning and behavioural problems. Additionally, illicit drugs may
containimpurities that may be harmful to unborn baby
10. Medical
concerns like depression and anxiety can severely interrupt the
addict‘ssocial and professional life, leading to mood swings, chronic
fatigue and a diminishedinterest in former hobbies and important life
events.
Preventive and Control
Measures of Drug Abuse
Suggest preventive and
control measures of drug abuse
Drug
abuse is a serious psycho-sociological problem often difficult to be
cured. The bestway to avoid these tragedies is to never start taking
drugs. However, nowadays specifictreatments are available for different
types of mental illness. A regular, prolonged andsincere treatment is
required .Social therapy or rehabilitation has got a very
significantrole. The following activities can be done for the control of
drug addiction:
1. Early detection, treatment and rehabilitation
of drug addicts can help minimize theproblem.
2. Parents should set a warm and friendly
atmosphere at home so that the drug users canfeel easy to cooperate with.
3. Motivation of the addicts to make up for
detoxification.
4. The youth should be motivated to get involved
in the fight against drug abuse.
5. Educating the community about the problems of
drug addiction.
6. Enforcement of laws, rules and regulation for
the control and supply of drugs.
7. The
school curricula should contain courses about the drug addiction and
drug abusein detail (like the topic you are reading now).
8. Various
effects of drug addiction must be advertised through newspapers,
radio,television, magazine, social media, and many other media so as to
make the problemknown to as many people as possible.
9. The
experience of drug users can be advertised to the people through media
to makethe general public aware of the effects of drugs so as to
discourage those who mightthink of starting taking drugs.
Location of the
Different Endocrine Glands in the Mammalian Body
Identify location of
the different endocrine glands in the mammalian body
THE ENDOCRINE SYSTEM
The
endocrine system is a collection of glands that produce hormones which
regulatemetabolism, growth and development, tissue function, sexual
function, reproduction,sleep, and mood, among other functions. The
glands are located in various parts of thehuman body. The function of
these glands is to release various hormones, and as a whole,they are
most commonly referred to as the endocrine system. These glands are
pituitarygland, hypothalamus, thymus, pineal gland, testes, ovaries,
thyroid, adrenal glands,parathyroid and pancreas. The location of these
glands in the human body is as shown inthe diagrams below.
The role of Hormones
produced by each Endocrine gland
Explain the role of
hormones produced by each endocrine gland
The
hormones released by glands of the endocrine system regulate the
functions of manycells and organs as indicated in the following table.
Disorders of Hormonal
Coordination in Mammals
Outline disorders of
hormonal coordination in mammals
Causes of endocrine
disorders
The causes of
endocrine disorders are typically grouped into two categories:
1. Endocrine disease that results when a gland
produces too much or too little of anendocrine hormone, called a hormone
imbalance.
2. Endocrine
disease due to the development of lesions (such as nodules or tumours)
inthe endocrine system, which may or may not affect hormone levels.
The
endocrine’s feedback system helps control the balance of hormones in
thebloodstream. If your body has too much or too little of a certain
hormone, the feedbacksystem signals the proper gland or glands to
correct the problem. A hormone imbalancemay occur if this feedback
system has trouble keeping the right level of hormones in
thebloodstream, or if your body doesn’t clear them out of the
bloodstream properly.
Increased or decreased
levels of endocrine hormone may be caused by:
1. A problem with the endocrine feedback system.
2. Disease.
3. Failure
of a gland to stimulate another gland to release hormones (for example,
aproblem with the hypothalamus can disrupt hormone production in the
pituitarygland).
4. A genetic disorder, such as multiple endocrine
meoplasia or congenitalhypothyroidism.
5. Infection.
6. Injury to an endocrine gland.
7. Tumour
of an endocrine gland.Most endocrine tumors and nodules (lumps) are
non-cancerous. They usually do notspread to other parts of the body.
However, a tumor or nodule on the gland may interferewith the gland’s
hormone production.
Types of endocrine
disorders
There
are many different types of endocrine disorders. Majority of endocrine
disorderscause the endocrine glands to produce too much (hypersecretion)
or too low(hyposecretion) of a given hormone from a particular gland.
Common problems thatresult from oversecretion (hypersecretion) or
undersecretion (hyposecretion) of givenhormones from given endocrine
glands are explained below.
PITUITARY GLAND
Hypersecretion
of growth hormone: Gigantism in children and acromegaly in adults.If
the pituitary gland produces too much growth hormone, a child’s bones
and body partsmay grow abnormally fast.
Hyposecretion of growth hormone: Pituitary dwarfism – if the condition occurs
duringchildhood, it slows down long bone growth.
Hypersecretion of ADH:
Causes increased reabsorption of water in the kidney tubulesleading to
production of a little urine but which is more concentrated.
Hyposecretion
of ADH: Less water is absorbed from the glomeruli filtrate back to
thebody, leading to production of large volumes of dilute urine. This is
called diuresis and isa symptom of diabetes inspidus.
THYROID GLAND
Hyperthyroidism
1. Grave’s
disease: The most common cause for an overactive thyroid is an
autoimmunedisorder called Grave’s disease. Grave’s disease, considered
an autoimmune disease,shows elevated weight loss, nervousness, excessive
perspiration, nervousness, highmetabolic rate and rapid, irregular
heartbeat.
2. Exophthalmos: protrusion of the eyeballs
caused by oedematous tissue behind theeyes.
Hypothyroidism
1. Cretinism
(infantile hypothyroidism) – shows stunted growth, thickened
facialfeatures, abnormal bone development and mental retardation.
2. Myxedema
– low metabolic rate, lethargy (a condition characterized by
extremefatigue or drowsiness, or prolonged sleep patterns.), weight
gain, increase in bodyfluids.
3. Goitre – abnormal growth of the thyroid gland.
PARATHYROID GLAND
Hyperparathyroidism:
demineralization of bone resulting in possible bone deformityand fracture, and
stones in the urinary tract
Hypoparathyroidism:
decreased plasma calcium levels which can lead to severe muscletetany
(a condition characterized by or resulting from uncontrolled muscle
spasms).
PANCREAS
Hyperinsulinism:
The liver is overstimulated to convert excess glucose to glycogen
andfats for storage. This leads to low glucose concentration in the
blood, a condition calledhypoglycemia. This condition results in lack of
glucose delivery to the brain causingdisorientation, unconsciousness
and even death (usually the result of an overdose ofinsulin).
Hypoinsulinism:
Under-secretion of isulin causes very little glucose to be converted
toglycogen and fats. This results in elevated glucose levels in the
blood and urine. Thecondition is called hyperglycaemia, and is a symptom
of diabetes mellitus. Over time,diabetics experience vascular and
neural problems. Secondarily, poor circulation maylead to gangrene,
blindness, kidney damage and impotence.
ADRENAL GLAND
Hypersecretion
of corticosteroids: Cushing’s syndrome – changes in carbohydrate
andprotein metabolism resulting in a puffy appearance.
Hyposecretion
of glucocorticoids and mineralocorticoids: Addison‘s disease -symptoms
of the disease include fatigue, stomach upset, hypoglycaemia, sodium
andpotassium imbalance, dehydration, hypotension, and rapid weight loss.
Death occurs withlack of treatment.
Hypersecretion
of adrenaline: hypertension, obesity, headache, increased
heartbeat,weak bones, hyperglycaemia, nervousness, sweating and early
onset of sexualdevelopment.
Hyposecretion
of adrenaline: low blood pressure, fatigue, muscular weakness,
musclewasting, inability to withstand stress, and increased dark
pigmentation of the skin.
OVARIES
Hypersecretion of
oestrogen: Causes decreased sexual desire, heavy menstrual flow andincreased
weight in females.
Hyposecretion
of oestrogen: Causes failure of females to develop some secondarysexual
characteristics, poor development of the reproductive organs, liver,
kidney andlungs.
TESTES
Hypersecretion of
testosterone: Causes males to have female features such as enlargedbreasts and
a wide pelvis.
Hyposecretion
of testosterone: Causes failure of males to develop some
secondarysexual characteristics, poor development of the reproductive
organs and weak bones andmuscles.
THYMUS
Not responsible for
any effects of hypo or hyper secretion of thymosin.
PINEAL
Not responsible for
any effects of hypo or hyper secretion of melatonin.
Coordination in Plant,
Concept of Tropic and Nastic Responses
The Concept of Tropic
and Nastic Responses
Explain the concept of
tropic and nastic responses
COORDINATION IN PLANTS
Both,
plants and animals react (or respond) to various stimuli around them.
But themethod of reacting to stimuli is not similar in plants and
animals. They react to stimuli indifferent ways. For example, plants
bend towards light but animals do not bend towardslight. The animal
amoeba reacts to the presence of food by moving towards the
foodparticle.
The
plants do not have a nervous system and sense organs like eyes, ears,
or nose, etc.,like the animals, but they can still sense things. The
plants can sense the presence ofstimuli like light, gravity, chemicals,
water, and touch, etc., and respond to them. Theysense these stimuli by
using hormones in them.
The
stimuli like light, gravity, chemicals, water, and touch, etc., are
called environmentalchanges. So, we can also say that the plants
coordinate their behaviour againstenvironmental changes by using
hormones. The hormones in plants do not act the sameway as in animals.
The
hormones in plants coordinate their behaviour by affecting the growth
of a plant.And the effect on growth of the plant can result in the
movement of a part of the plantlike shoot (stem) or root, etc towards a
certain stimulus.
Experiments to
Investigate the Effects of Tropic and Nastic Responses in Plants
Carry out experiments
to investigate the effects of tropic and nastic responses in plants
Plants
receive and respond to a variety of stimuli that are important to their
survival in theenvironment. These responses allow the plants to
survive, grow, develop and reproduce.The movement of plants in the
direction of stimulus is known as ‘tropism’. Tropisms aregrowth
responses of plants that result in curvatures of plant organs toward or
away fromcertain stimuli. Tropisms can be positive, in which case the
plant will bend toward astimulus, or negative, in which case the plant
will bend away from a stimulus.
The
other movements shown by the plants are associated with the growth of
the plants.For example, the shoot system moves towards sunlight and the
root system towards earth.Thus, the plants also respond to their
environment.
Important tropisms in
plants include phototropism, geotropism, hydrotropism,chemotropism and
thigmotropism.
Phototropism
Phototropism
is the tendency for plant organs to bend in response to a directional
lightsource. For example, light streaming in a window from one direction
will often cause thestems of plants placed nearby to bend toward the
window, a positive phototropism.
Most
plant shoots are positively phototropic because they tend to grow
towards light.Most roots are negatively phototropic because they away
from light.
The Importance of
Tropic and Nastic Responses
Explain the importance
of tropic and nastic responses
Importance of
phototropism
Phototropism
is important to plants because of it enables the plant leaves to be
placedunder direct sunlight to absorb maximum light so as to carry out
photosynthesiseffectively.
Geotropism
Geotropism
is the movement of a part of the plant towards gravity. In most plants,
rootsgrow downward with gravity while shoots grow upward against
gravity. Within hours,the shoot of a plant placed on its side will
usually bend upward and the roots will benddownward as the plant
reorients its direction of growth in response to gravity.
Most
plant roots grow towards gravity and are said to be positively
geotropic. Mostshoots grow away from gravity and are said be negatively
geotropic.
Importance of
geotropism
Geotropisms are
important to plants because of the following reasons:
1. It enables the plants to send roots into the
ground hence anchoring the plant firmlyinto the soil.
2. It enables plant roots to absorb water and
mineral salts from the soil.
3. Negative
geotropism exhibited by the shoot enables the shoot to grow upwards,
andin so doing, exposes the plant leaves to maximum sunlight for
effectivephotosynthesis
Hydrotropism
Hydrotropism
is the movement of a plant or part of a plant towards water. Plant
rootsnormally grow towards moisture. They are therefore positively
hydrotropic. If you plant aplant near a water source such as porous pot
or river, the roots will always grow towardswater.
Importance of
hydrotropism
It enables the plants
to absorb dissolved minerals and water. Water is necessary forvarious functions
such as:
1. Photosynthesis
2. Numerous physiological reactions that take
place within plant cells.
3. Turgor pressure, which aids in plant support.
4. Dissolution of mineral salts.
Chemotropism
An
example of positive and negative chemo-tropism is shown by a plant‘s
roots; the rootsgrow towards useful minerals displaying positive
chemo-tropism, and grow away fromharmful acids displaying negative
chemo-tropism.
Chemotropism
is the movement or growth of an organism or part of an organism
inresponse to a chemical stimulus. During the process of fertilization
the movement ofpollen tube towards ovule due to secretion of a sugary
chemical in the ovary is anexample of chemotropism
Importance of
chemotropism
1. It enables the plant to absorb mineral salts
from the soil when the roots grow towardsbeneficial chemicals such as
fertilizers.
2. Negative
geotropism, such as when plant roots grow away from the toxins,
enablesthe plant to survive by avoiding contact with such harmful
chemicals.
3. . It facilitates the fertilization process in
flowering plants.
Thigmotropism or haptotropism
Thigmotropsim
refers to non-directional movements which take place neither towards
noraway from the stimulus. The best example of nastic movement is
folding and drooping ofleaves of Mimosa pudica plant when its leaves are
touched with fingers or any object.The leaves fold even when swayed
about by wind. Also the specialized touch-sensitivetendrils of many
vining plants, such as pea, will bend toward the side receiving a
touchstimulus. Continual stimulation can lead to the coiling of the
tendril around an object,which enables vining plants to grasp objects on
which they can climb
Importance of
thigmotropism
1. Thigmotropism enables crawling plants to climb
up higher plants and expose theirleaves to sunlight for optimum photosythesis.
2. It enables the insectivorous plants such as
the Venus flytrap to trap insects and digestthem to obtain nutrients.
BIOLOGY
FORM THREE TOPIC 4: EXCRETION
Concept of Excretion
The Concept of
Excretion
Explain the concept of
excretion
Chemical
reactions occur in the cells of living organisms all the time to carry
out the life processes. The sum of these reactions is called metabolism.
Metabolism produces useful products as well as toxic (poisonous)
by-products.
These
toxic substances have to be removed as they are harmful if allowed to
accumulate. The removal of metabolic waste products from the body of an
organism is known as excretion.
The
major excretory products are carbon dioxide, excess water, and
nitrogenous compounds like ammonia, urea, uric acid, etc. Carbon dioxide
and water are produced in the process of tissue respiration.
Nitrogenous compounds are formed from the breakdown of proteins and
amino acids. Water and salts in excess of the body’s needs are also
excreted.
Other
excretory products include chemicals from medicines, toxic substances,
and circulating hormones that have already served their purpose. We will
learn how metabolic wastes get eliminated.
In
concise, excretion is the process by which waste products of metabolism
and other non-useful materials are eliminated from an organism.
Examples of Excretory
Products Eliminated by Organisms
Give examples of
excretory products eliminated by organisms
Living
organisms excrete various excretory products of diverse chemical
nature. The following are examples of excretory products excreted by
living organisms:
· Carbon dioxide:This
is a by-product of respiration of both plants and animals. It is
excreted through the pores of the stomata in plants (some of the carbon
dioxide produced by respiration is used in photosynthesis). In man,
carbon dioxide is eliminated from the body by lungs.
· Water:The
concentration of water in cells must be kept within narrow limits. Too
little or too much water can have a negative effect on the osmotic
condition in and around the cell. Therefore, it has to be regulated.
Plant cells are protected from bursting by their cell walls. Animals do
not have cell walls, and will burst if they have too much water. Excess
water is lost from the surface of gaseous exchange in both plants and
animals. In mammals, water is also lost through sweat and through
osmoregulation controlled by the kidneys.
· Urea:This
is a compound produced in mammals from the breakdown of excess amino
acids. Amino acids cannot be stored because their accumulation is toxic.
They are therefore converted into a less toxic substance. This process
occurs in the liver and is called de-amination.Ammonia is converted to
urea by the liver. Urea is transported by blood to the kidneys where
they are excreted. The kidneys are also used to remove uric acid, water,
excess salts, excess hormones and bile pigments.
· Calcium oxalate:This
is a waste material produced by plants and is stored as an insoluble
crystalline structure in the cells. Calcium oxalate is stored in aging
leaves, stems and roots, flowers or fruits.
· Oxygen:Through
the process of photosynthesis, oxygen is produced as a by-product. Some
of the oxygen is used for respiration, and the remainder is excreted
through the stomata of the leaves.In plants, some waste substances are
stored in parts of the plant that are dead. Examples of this are the
tannin in the bark of trees such as mangroves and the dyes in the
heartwood of trees such as logwood. The purpose of the storage of waste
material ranges from protection to a decreased risk of being consumed.
Excretion in Human
The
main excretory system in humans is the urinary system. The skin also
acts as an organ of excretion by removing water and small amounts of
urea and salts (as sweat). The urinary system includes a pair of
bean-shaped kidneys located in the back of the abdominal cavity.
Excretory Organs in
Human Being
Mention excretory
organs in human being
There
are special organs concerned with removal of excretory products from
the body. Such organs are called excretory organs. The excretory organs
in an animals body are the kidney, the skin the lungs and the liver. The
following table shows the excretory organs and the products they
excrete.
The
table below summarizes excretory products in humans and the organs
concerned with excretion of the product and the mode of excretion.
|
Excretory product |
Organ |
Mode of excretion |
|
Carbon dioxide |
Lungs |
Exhalation |
|
Urea and excess mineral salts |
Kidneys |
Urine |
|
Skin |
Sweat |
|
|
Excess water |
Kidneys |
Urine |
|
Skin |
Sweat |
|
|
Lungs |
Water vapour |
|
|
Bile pigments (from breakdown of haemoglobin) |
Liver |
Faeces |
A
comparison between different excretory products can be made. Following
is the comparison between different types of excretory products:
|
Waste |
Advantages |
Disadvantages |
Habitat |
Excreted by |
|
Ammonia |
Produced with little energy |
Toxic in concentrated solution. Excretion take place in
lot of water |
Water |
Marine and fresh water invertebrates, bony fishes,
amphibians |
|
Urea |
Less toxic than ammonia. Less water is needed to excrete
it |
Requires more energy to produce it |
Land, Sea |
Adult amphibians, turtles, mammals and bony fishes |
|
Uric Acid |
Very little water is used for its excretion |
Requires considerable energy to produce it |
Land |
Reptiles, birds, insects, gastropods (snails and slugs) |
|
Guanine |
Relatively non toxic. Less water is used to excrete it |
More energy is needed |
Arid habitat |
Scorpions, Spiders |
The excretory organs
in humans beings may conventionally be put into two groups namely, primary and
accessory organs:
Primary excretory organs
1. Kidneys:Kidneys
are bean-shaped organs of a reddish brown colour that are found in the
sides of the vertebral column. Once the body has extracted wastes from
food, it sends the wastes to the kidneys. The kidneys filter the wastes,
including urea, salt and excess water, which are flushed out of the
body as urine.
2. Skin:The skin performs
its excretory function via the sweat glands. These are coiled tubules
surrounded by blood capillaries. These glands produce sweat that
contains mineral salts, excess oils, water, and traces of urea and
lactic acid from the surrounding blood vessels which are then excreted
out of the body through sweat pores. The tubules extend into sweat ducts
which open on the surface of the skin as pores. Sweating also helps to
cool the body during evaporation.
3. Lungs:The
lungs are very important excretory organs as they expel carbon dioxide
from the body via exhalation. The lungs use cells known as alveoli to
remove the carbon dioxide from our blood. Otherwise, the carbon dioxide
would accumulate and have a detrimental effect to our body.
Accessory excretory organs
1. Liver:Although
considered a secondary or accessory excretory organ, the liver plays a
vital part in keeping the body clean. Amino acids are the end-product of
proteins. Excess amino acids cannot be stored in the body. They are
taken from the gut into the liver by the hepatic portal vein. The liver
converts them into useful carbohydrates (stored in the form of glycogen)
and ammonia. Ammonia is very poisonous and must be removed from the
body. The liver converts ammonia into a harmless compound called urea.
Urea dissolves in the blood and is transported into the kidney via the
hepatic vein where it is removed as component of urine.Harmful poisons
and chemicals that are either produced in the body or consumed are
broken down and detoxified by the liver.
2. Gall bladder:Although
the gallbladder does not have a highly significant role to play in the
excretory system, it does have a function that assists the overall
process. Bile, a liquid produced by the liver to break down waste, is
first stored in the gall bladder. When needed, it is discharged into the
small intestine whose role is to break down fats, ethanol and other
acidic wastes.
3. Urinary bladder:The
waste fluid that is created in the liver and collected in the kidney is
transferred into the urinary bladder where it is temporarily stored
until the individual urinates. The urinary bladder provides a short term
solution for storing urine in the body until it is ultimately
discharged.
4. Ureters:The ureters tubes
of smooth muscle fibre transfer liquid waste from the kidneys into the
urinary bladder. The urine is moved with peristaltic movements which
force the urine away from the kidneys. The ureters also have
ureterovesical valves which ensure the waste fluid does not travel back
into the kidney.
5. Urethra:The urethra
runs through the penis in males, and serves as a carrier of semen as
well as urine for their ultimate discharge out of the body. The urethra
tube is shorter in females and is just above the vaginal opening.
6. Large intestine:Food
particles are absorbed into the blood stream via the small intestine.
The undigested substances are transferred to the large intestine which
essentially serves as a storage organ for the excretory products. The
descending, ascending and transverse colons also facilitate the
absorption of leftover vitamins, water and salt. The distal straight
section (known as the rectum) is used for the storage of waste products
(faeces) before they are excreted from the body via the anal canal with
the help of internal and external sphincters.
The Urinary System and
its Adaptive Features
Describe the urinary
system and its adaptive features
The
urinary system is a system concerned with production, storage and
removal of urine. In humans, it is made up of the two kidneys, ureters,
blood vessels that join them, urinary bladder and urethra.
The human urinary system
Each
kidney is connected to a urinary bladder by a tube called the ureter.
As urine is formed, it passes through the ureter to the urinary bladder
where it is stored temporarily. Below the bladder is a tube called
urethra which is surrounded by a ring of muscles called sphincter
muscles. The urethra is a canal that carries urine from the bladder and
expels it outside the body. The urethra passes urine when sphincter
muscles relax.
The kidneys:Kidneys
are bean-shaped organs that are deep red in colour located on the
dorsal part of the abdominal cavity. Mammals have one pair of kidneys.
Kidneys are the principle organs of the urinary system.
Functions of the kidneys
1. They filter blood to remove wastes and
reabsorb useful substances such as water and salts.
2. They maintain appropriate water-salt balance
in the blood.
3. They regulate the acid-base balance such that
the pH of blood remains at about 7.4 for proper functioning of the body.
4. They are important in regulation of blood
pressure.
5. They
produce erythropoietin, calcitriol and an enzyme called rennin, which
is involved in the formation of the hormone, angiotensin, which raises
blood pressure. Erythropoietin is a hormone that speeds up the process
of the formation of red blood cells in the bone marrow. Calcitriol is an
active form of vitamin D which increases the rate of calcium
reabsorption for bone formation.
Structure of the kidney
Each
kidney is enclosed in a thin, fibrous covering called the capsule. The
kidney has three distinct regions, namely the cortex, medulla and
pelvis. The cortex is the outermost layer of the kidney. The medulla is
the middle layer of the kidney, normally red in colour. The pelvis is
the space inside the kidney which collects the urine and leads it to the
ureter. The ureter passes urine to the urinary bladder where it is
stored before it is released out through the urethra in the genitals.
Each
kidney is supplied with oxygen-rich blood from the renal artery.
Deoxygenated blood is returned to the circulatory system from the
kidneys via the renal vein. Blood entering the kidneys from the renal
artery are rich in waste materials, and blood exiting the kidneys from
the renal vein is deficient in these waste materials.
Structure of the kidney
The nephron
Each
kidney is made up of numerous, coiled excretory tubules known as
nephrons, and collecting ducts associated with tiny blood vessels.
A
nephron consists of a long, coiled tubule, and the Malpighian
corpuscle. The tubule of the nephron is differentiated into the proximal
convoluted tubule, loop of Henle and the distal convoluted tubule. The
distal tubule opens into the collecting duct.
At
the proximal end of the nephron is the Malpighian corpuscle, which
consists of Bowman’s capsule and the glomerulus. Bowman’s capsule is a
double-walled, cup-like structure which surrounds the dense network of
blood capillaries called the glomerulus.
Structure of the nephron
There is a branch of
the renal artery,the afferent arteriole,
entering the small cup-like space of theBowman’s capsuleas a network of
blood capillaries. This network is known as theglomerulus. Emerging
from this network, the capillaries re-unite to form a small arteriole,
known asthe efferent arteriole. As the efferent
arteriole continues it twines around the proximal and distal convoluted
tubule. The efferent arteriole divides into capillaries at several
points along the length of the tubules, absorbing various substances.
These capillaries eventually reunite to drain into the renal vein. The
efferent arteriole is smaller than the afferent arteriole. This
difference in diameter helps to raise the glomerular pressure and aids
in ultra filtration.
Some
animals do not have a well developed kidney; they may have structures
called nephridia. Animals such as earthworms that are simple tube-like
structures have nephridia that have the same role as the more complex
nephrons in the kidneys.
The Process of Urine
Formation
Explain the process of
urine formation
The
blood from the afferent arteriole, which enters the Bowman’s capsule,
is rich in nutrients such as glucose, fatty acids, amino acids,
vitamins, proteins, urea and excess salts. A nephron is the structural
and functional unit of a kidney which is concerned with excretion and
haemostasis.
The
three (3) distinct stages of urine formation are: (1) glomerular
filtration, (2) tubular reabsorption and secretion, and (3) water
conservation
1. Glomerular filtration:Filtration
occurs in the glomerulus (plural; glomeruli). Because the lumen of the
afferent arteriole is significantly smaller than the efferent arteriole
there is a large amount of pressure in the glomerulus. This pressure
forces forces plasma, the liquid portion of the blood, through the
capillary walls in the glomerulus. The plasma contains water, glucose,
amino acids, urea, salts, uric acid, vitamins, and hormones. Red blood
cells and proteins are retained in the blood capillaries because they
are too large to pass through the wall. This process is called
ultra-filtration and the fluid which passes into the Bowman’s capsule is
known as the glomerular filtrate.The glomerular filtrate collects in
the capsule and enters the renal tubule at the proximal convoluted
tubule which is coiled to increase the surface are for reabsorption of
substances.
2. Reabsorption and
secretion:The
efferent arteriole branches into capillaries which surround the proximal
convoluted tubule. There, glucose, amino acids, vitamins, hormones and
about 80% of sodium chloride and water are reabsorbed into the blood
capillaries. Only the substances that are useful to the body are
reabsorbed. This is referred to as selective reabsorption. Normally 100%
of glucose is reabsorbed. Blood cells are not reabsorbed due to their
large molecular size. Reabsorption involves both diffusion and active
transport (against concentration gradient), which uses energy in the
form of ATP. The waste-containing fluid that remains after reabsorption
is urine. Tubular secretion is the passage of certain substances out of
the capillaries directly into the renal tubules. Tubular secretion is
another way of getting waste materials into the urine. For example,
drugs such as penicillin and phenobarbital are secreted into the renal
tubules from the capillaries. Urea and uric acid that may have been
reabsorbed are secreted. Excess potassium ions are also secreted into
the urine. Tubular secretions also maintain the pH of the blood.
3. Water conservation:In
the distal convoluted tubule, water is reabsorbed into the blood by
osmosis. The tubule is also highly coiled to increase the surface area
for reabsorption. The glomerular filtrate then flows into the collecting
tubules where more water is reabsorbed. The filtrate now called urine
flows into the collecting duct then into the pelvis of the kidney. It
then flows into the ureter and is temporarily stored in the bladder.
When it gets full, impulses are sent to the brain to create an awareness
of the presence of urine in the bladder. A person then fells the need
to urinate and the bladder muscles contract, sphincter muscles relax and
the urine is expelled via the urethra.Urine formation is essential for
maintaining homeostasis, which is the ability of the body to maintain
constant internal environment.
Reabsorption and secretion by the nephron
Adaptations of the urinary system to its functions
1. The
urinary system has a large afferent arteriole, and narrow efferent
arteriole, which allows build up of pressure, thus facilitating
ultra-filtration.
2. The glomerulus capillaries are highly coiled
and semi permeable, causing a build up of pressure in the glomerulus
hence ultrafiltration.
3. The glomerular capillaries are semi
permeable (tubule also semi permeable) to allow selective movement of
materials in and out of the nephron (selective reabsorption).
4. The
tubules’ epithelium is thin (1 cell thick) to reduce diffusion distance
for faster passage and hence reabsorption of materials; and they are
and leakier than normal capillaries.
5. It is connected to a
collecting duct, which channels the filtrate (urine) out of the nephron
to the ureter to allow for continous functioning of the nephron.
6. The
proximal convoluted tubule and the distal convoluted tubule are coiled
so as to increase the nephrons’s length and hence more surface area for
efficient reabsorption to take place.
7. The Bowman’s capsule is cup-shaped to provide
maximum surface area for filtration.
8. The tubule is supplied with a network of blood
capillaries for maximum reabsorption.
9. The nephrons are numerous in number for
efficient excretion of waste products.
Complications and
Disorders of the Excretory System
Common Complications
and Disorders of the Excretory System
Mention common
complications and disorders of the excretory system
A
large number of medical conditions of varying intensity are associated
with the excretory system. If these are not addressed immediately, they
may even prove to be fatal and claim one’s life. We need to be well
acquainted with the most commonly occurring diseases of excretory system
along with their description, symptoms and effective treatment
measures. The table below shows some of the common complications and
disorders of the excretory system, their causes, symptoms, effects and
preventive measures.
The Causes, Symptoms,
Effects and Control Measures of Common Complications and Disorders of the
Excretory System
Explain the causes,
symptoms, effects and control measures of common complications and disorders of
the excretory system
Disorders of the
Excretory System
|
Disease |
Cause(s) |
Symptoms |
Effects |
Prevention/treatment |
|
Kidney (renal) failure – failure of the kidney to function adequately due to
partial or entire destruction of nephrons |
· Damage to the kidney due to accident or complications
during surgery · Low blood volume due to excessive bleeding · Poor intake of fluids · Medication, for example, diuretics (“water pills”) may
cause excessive water loss · Obstruction of renal artery, causing blocking of blood
flow to the kidneys · Kidney stones · Chronic diseases that gradually cause the kidneys to stop
functioning · Dehydration from loss of body fluid (for example,
vomiting, diarrhoea, sweating, fever) · Prostate cancer may block the urethra and prevent the
bladder from emptying |
· Oedema (swelling of the legs, ankles, feet, face or hands
due to excess fluids) · High levels of urea in blood leading to vomiting, nausea,
weight loss, blood in urine or difficulty in urinating · Loss of appetite |
Bone |
· Avoid potassium-rich foods like citrus fruits, bananas,
instant coffee, peanuts and chocolate · May require a kidney transplant. · Medications e.g. phosphorus-lowering medications. · Dialysis |
|
Kidney stones |
· Lack of vitamins · Inadequate intake of water · Certain types of drugs · Decrease in urine volume and/or an excess of stone-forming
substances in the urine. · Dehydration from reduced fluid intake or strenuous
exercise · Obstruction to the flow of urine · Infection in the urinary tract |
· Extreme pain and difficulty in urination · Pain in the low back and/or side, groin, or abdomen · Blood in the urine due to damage of the inside walls of
the kidney, ureter or urethra · Nausea and vomiting · Chills and fever |
· May lead to kidney failure · Toxicity due to urine staying in the body for a long time · Severe back pain · Surgery and medications are expensive |
· Taking a balanced diet that is low in protein, nitrogen
and sodium · Drinking plenty of water · Avoid beverages that contain caffeine like coffee. · Surgical treatment to remove the stones · May require kidney transplant · Medications (painkillers) |
|
Urinary tract infections (UTIs) |
· Bacterial infection in the urinary tract |
· Frequent or intense urge to urinate even though little
comes out when you do · Pain during urination · Pain or pressure in the back or lower abdomen · Cloudy, dark, bloody, or strange-smelling urine · Feeling tired or shaky · Fever or chills (a sign the infection may have reached
your kidneys) |
· Medications are expensive. · Pain and nuisance due to urge to urinate frequently. |
· Drinking a lot of fluids · Maintaining toilet hygiene · Complete urination · Cleanse genital area before sex · Urinate after sex to flush away any bacteria that may have
entered your urethra · Keep genital area dry by wearing cotton underwear and
loose-fitting clothes |
|
Liver cirrhosis: |
· Alcohol and viral hepatitis B and C · Attack by bacterial and viruses · Parasites such as liver flukes and schistosoma · Obstruction of the gall bladder · Exposure to chemical poisons such as silica and asbestos |
· Loss of weight · Poor appetite · Abdominal pain · Blood stained vomit |
· Severe cirrhosis is fatal · Easy bruising, yellowing of the skin (jaundice),itching,
and fatigue. · Oedema, ascites (accumulation of fluid in the abdominal
cavity), and liver cancer |
· Avoiding excess consumption of alcohol · Avoiding fatty foods · Low salt intake · Eating varied, easily digestible food · Plenty of rest · Medical treatment · Liver transplant in case of severe cirrhosis |
|
Hepatitis:Inflammation of the liver |
· It is a viral disease–virus is transmitted through body
fluids such as saliva, blood and semen · There are five main types of hepatitis: A, B, C, D, and E
– plus types X and G |
· Nausea · Fatigue · Abdominal discomfort · Jaundice · Dark brown urine and whitish faeces |
· May lead to liver failure · If not treated early may lead to death |
· Hygienic processing of food · Proper disposal of sewage · Treatment of water · Proper handing of blood · Screening blood before transfusion · Using sterilized needles and syringes |
|
Bladder Cancer |
· Not |
· Blood in urine. · Frequent urinary tract infections, painful urination and
urge to urinate without actual flow. · Weight or appetite loss. · Abdominal or back pain, persistent raised temperature or
anaemia. |
· Expenses on medication. · Pain – reduces the |
Excretion in Plants
Types of Excretory
Products Eliminated by Plants
Mention types of
excretory products eliminated by plants
Excretion
occurs in plants and animals as they both have waste products to be
removed from their bodies. Compared to animals, plants do not have a
well-developed excretory system to throw out nitrogenous waste
materials. This is because of the differences in their physiology.
Therefore, plants use different strategies for excretion.
Plants
eliminate some waste through diffusion. During the day, excess oxygen
gas produced by photosynthesis is released through the stomata. Carbon
dioxide produced by respiration is normally used up during
photosynthesis. At night, however, as photosynthesis slows down, carbon
dioxide is not used up as fast as it is produced, and it is released as a
waste product. Plants also produce oxygen as a by-product of
photosynthesis. The oxygen that is not used for respiration is also
excreted through the stomata.
Excess
water evaporates mostly from stomata and also from the outer surface of
the stem, fruits, etc., throughout the day. This process of getting rid
of excess water is called transpiration.
Many
plants store organic waste products in their permanent tissues that
have dead cells, e.g., in heartwood. Plants also store waste within
their leaves or barks. These wastes are periodically removed as the
leaves and barks fall off.
Some
of the waste products are stored in special cells or cellular vacuoles.
Various waste products such as tannins, essential oils, gums, resins,
etc., are produced during catabolic processes. Tea leaves contain
tannin. Tannins are found also in the barks of trees.
The
leaves of many plants, like Eucalyptus, lemon, etc., contain essential
oils. The coating of oranges and lemons and the petals of flowers like
rose and jasmine also contain oils. Some plant wastes are stored as a
thick, white fluid. You may have seen white fluid ooze out when you
pluck a papaya or a fig or other plants. This white fluid is called
latex.
Gums
are a group of sticky, water- soluble wastes found in the common gum
tree. Resins are another group of wastes found commonly in the stems of
conifers (e.g., pine, fir).
Alkaloids
are a group of toxic waste products. But some of these are useful to
us. Quinine and morphine are medicines derived from alkaloids stored in
Cinchona bark and opium poppy flowers respectively. Caffeine found in
coffee seeds and nicotine in tobacco leaves is also alkaloids.
Plants
also eliminate waste by the accumulation of waste in the vacuoles of
the aging leave cells. These leaves will eventually die and fall off,
removing waste in the process. This process is called abscission.
Organic
acids, which might prove harmful to plants, often combine with excess
cations and precipitate out as insoluble crystals that can be safely
stored in plant cells. Calcium oxalate crystals accumulate in some
tubers like yam.
Aquatic
plants lose most of their metabolic wastes by direct diffusion into the
water surrounding them. Terrestrial plants excrete some waste into the
soil around them.
In
plants, breakdown of substances is much slower than in animals. Plants
do not have specialized excretory organs for the removal of metabolic
wastes.
Plants do not need a
specialized excretory system like in animals because of the following reasons:
a. The rate of producing waste products in plants
is much lower.
b. Most
excretory products from plants are removed by diffusion through the
stomata or lenticels. Lenticels are areas in woody stems where the cells
are loosely packed allowing gaseous exchange and removal of waste
products.
c. The major excretory products of plants are
carbon
dioxide, oxygen and water. These products are recycled. For example, the
oxygen released as a by product during photosynthesis, is used in
respiration by animals and plants. The carbon dioxide released during
respiration is used for photosynthesis by the plants. Water is released
into the atmosphere where it enters the water cycle.
d. Plants produce less poisonous substances
compared to the nitrogenous wastes produced by animals.
e. Plants
have large vacuoles which store waste substances often accumulating at
concentrations that lead to crystal formation in form of oil droplets or
granules.
f.Plants can also store the waste products in
organs
that are destined to fall or die off. So they can be excreted via
abscission. Other waste material such as resins, saps and latexes are
forced out from the interior of some plants by hydrostatic pressure
inside the plant.
The Importance of
Common Excretory Products of Plants
Explain the importance
of common excretory products of plants
Have
you ever noticed sticky, milky or oily substances being oozed from the
bark of trees? These are excretory products and may be resins, gums,
latex and or other excretory products. These products may be poisonous.
However, many have found use in everyday life of humans, such as latex
which is used to produce gloves and clothing. The table below shows
functions of some plant waste products.
|
Product (waste) |
Plant source |
Use and effects |
|
1. Tannins |
Dead tissues of plants such as acacia, conifers, coffee
and mangroves. |
· Treatment/tanning · It is used in the manufacture of inks and dyes. |
|
2. Alkaloids: Are nitrogenous
excretory products in plants and occur in various forms- Common alkaloids
include: |
||
|
(a) Caffeine and theophilinet |
-Coffee fruits and tea leaves |
-Mild stimulants to increase
mental activity and reduce fatigue. |
|
(b)Quinine |
– Bark of cinchona tree. |
-A drug for the treatment of
malaria.-An additive in drinks to act as a stimulant. |
|
(c) Cocaine |
– Leaves of coca plant |
· A very expensive drug for local anaesthetics. · A painkiller and also gives great mental and physical
strength. · Note: Overdose may lead to hallucinations, anxiety and
even death. |
|
(d) Cannabis |
-Fruits, flowers and leaves of
cannabis sativa (bhang or marijuana) |
· Manufacture of drugs such as painkillers. · Results in relation, talkativeness, and greater
appreciation of sound and colour. · Decreased performance in concentration, intellectual and
manual tasks. · Overdose effects are similar to that of cocaine. |
|
(e) Opiates(morphine) |
-Opium poppy |
Manufacture |
|
(f) Nicotine |
-Tobacco leaves. |
· Manufacture · A common cause of respiratory and cardiac diseases, due to
tar from its smoke. |
|
(g) Papain |
-Epicarp of pawpaw fruits
(especially raw). |
-Has proteolytic activity hence
used as a meat tenderizer. |
|
(h) Colchicine |
-Roots of the crocus plant. |
· Interferes with the process of cell division resulting
into mutations; and thus useful in plant breeding. · It is also carcinogenic (cancer–causing). |
|
(i) Pyrethrins |
-Flowers of pyrethrum |
Making of insecticides |
|
(j) Khat (miraa) mirungi) |
-Leaves and twigs of the “khat”
plat |
-Used as a stimulant. |
|
3. Latex |
· -Rubber tree · Sapodila |
· Manufacture of shoe soles, tyres, etc. · Manufacture of chewing gum. |
|
4. Gums |
Different plants such as Arabic
ghath and carob, acacia tree, etc. |
· Most are edible and thus used to thicken foods and creams. · Gum from sapodilla is used to make chewing gum. · Agar extract (a gum) from algae is used as a growth medium
to culture microorganisms. · It is also used to make cough medicine. |
|
5. Anthocyanins |
-Petals and leaves of various
plants, and are mostly red, blue or purple. |
· Extracted for making dyes. · Used in making PH indicators. |
|
6.Digitalis glycosides |
-Foxglove |
Manufacture of drugs used for
treatment of heart diseases such as digitoxin. |
|
7. Rennin |
-Certain tree stems like the
casuarina tree |
-Manufacture of varnish and gum. |
|
8. Oil |
-Flowers or leaves of certain
trees. |
Manufacture of perfume and
ointment for insect bites. |
BIOLOGY FORM
THREE TOPIC 5: REGULATION
Concept of Regulation
The Concept of
Regulation
Explain the concept of
regulation
Living
organisms are subjected to wide variations in temperature, light,
acidity, salinity, wind speeds, availability of water minerals and
nutrients. These environmental factors create a shifting external
setting to which organisms must adjust or die.
The
central problem for a living thing is to maintain a steady state
internally in the force of an often harsh and fluctuating external
environment.
Homeostasis
is the maintaining of a constant condition of the internal environment
of the body by regulatory process. OR It is the maintenance of constant
internal balance despite fluctuation in the external environment.
Regulation
is the process of controlling the internal body environment and needs.
For the body to function properly things need to be regulated in the
body.
Reasons that show importance of regulation
1. Maintaining favorable condition such as pH and
required ionic concentration for the functioning of cells, tissues and organs.
2. Enabling organisms to get rid of body wastes
and useless materials for example excess water and salts
3. Enabling organisms to get rid of excess
materials for example excess water and salts
4. Ensuring survival of the organisms
Various Types of
Regulation
Mention various types
of regulation
The following are the
types of regulation:
1. Temperature regulation (thermoregulation)
2. Blood sugar regulation
3. Osmoregulation
Temperature Regulation in
Animals
The Concept of
Temperature Regulation in Animals
Explain the concept of
temperature regulation in animals
HEAT GAIN BY ANIMALS
There are three ways
of heat gain by animals:
1. Metabolism of food stuffs
2. Shivering
3. Absorption of solar radiation
EAT LOSS BY ANIMALS
Animals lose heat
through:
1. Convection – This is flow of heat from the
interior of an animal’s body to exterior in the surrounding
2. Sweating/Evaporation – This occurs when animal
loose water vapour from their body surface
3. Conduction – This is transfer of heat by
physical contact between two bodies
4. Breathing out
5. Panting
6. Salivation
7. Defecation
8. Urination
Practical Activities
to Determine Temperature Regulation in Mammals
Carry out practical
activities to determine Temperature Regulation in Mammals
Activity 1
Carry out practical
activities to determine Temperature Regulation in Mammals
The Mechanism of
Temperature Regulation in Mammals
Describe the mechanism
of temperature regulation in mammals
Ectothermic animals
gain heat by:
1. Metabolism of food stuff
2. Solar radiation
3. Contractions of body muscles
Each species of
ectothermic animal has its own optimum temperature during which metabolic
activities can take place.
The graph below shows
the relationship between external temperature to internal temperature in
Ectothermic animal
When the environment
is over heated ectotherms:
1. Ectothermic animals example fish migrate to
places with a more suitable temperature for them
2. Use of shade – snakes, frogs, lizards take
shade to avoid being over heated
3. Pant – turtles and tortoise pant during hot
day to loose excess heat
When the environment
is over cooled ectotherms:
1. Burrow – toads burrow during cold conditions
to avoid over cooling
2. Bask – snakes, lizards and chameleons bask in
the sun to raise their body temperature
3. Social behavior – bees cluster together to
raise body temperature
4. Flex their body muscles e.g. python flex its
muscles and coil eggs during cold condition
5. Use of metabolic heat – bees contracts their muscles
using prior flying in cool weather to raise their body temperature.
Endothermic
animals gain heat only through metabolism of food substances. The
temperature ranges of these animals are as follows:
· Mammals 35oC – 40oC
· Birds 40oC – 45oC
Each
species of endothermic animal has their own optimum temperature during
which metabolic activities occur for example homo-sapiens 36.7oC, House fowl 41oC
Temperature
regulation in endothermic animals is a physiological process. It is
controlled by hypothalamus and contains two thermo receptors hot and
cold centers.
When the environment
is OVER HEATED:
· During hot conditions hot center in the
hypothalamus is activated by increase in blood temperature.
· Hypothalamus uses nerve impulses and hormones
as error signals to activate responses that increase heat loss from the body.
Examples
of error signals that activate responses that cause heat loss so that
the core temperature is brought to its set point are:
1. Sweating – Sweat glands secrete sweat and
sweat pores open. Sweat evaporates at the surface of skin with heat.
2. Vasodilation
– Vasodilation is the increase of size of the blood vessels near the
skin surface so that the heat is lost by radiation as a result of direct
contact of vessels with skin.
3. Flattening of body hairs: Hair erector muscles
on the surface of the body reduce insulation so that heat loss is simplified.
4. Panting
– This is a process of opening mouths and hanging out of tongue. Dogs
do this process. Panting causes heat loss by evaporation.
5. Closing
of stunt vessels, a process done by whales closing of stunt vessels
directs most of core blood to reach the skin and increase pressure
gradient between the skin and the environment hence heat is lost easily
to the environment
When the environment
is OVER COOLED:
Examples of corrective
mechanisms, which conserve body heat, are:
1. Shivering is a reflex shaking of muscles. The
process results into generation of heat.
2. Erection
of skin hairs: hair erector muscles erect causing the skin hair to
stand and collect air around them which act as insulation for heat loss.
3. Vasoconstriction
of blood capillaries: Vasoconstriction is a process of narrowing the
blood capillaries leading to the skin. This in turn reduces the
temperature gradient of the body and environment and heat loss
decreases.
4. Opening of shunt vessels, a process done by
whales.
Opening of shunt vessels and back to the internal blood circulation. The
process reduces heat loss to the surrounding
5. Increase in
metabolic activity. An increase in respiration is affected by an
increase in thyroxin secretion. During cold conditions, hypothalamus
stimulating hormone which in turn stimulates the secretion of thyroxin
hormone which influences fast respiration hence an increase in heat
gain.
EFFECT OF OVER HEATING
If the core temperature
rises above 40oC
the thermo-regulating mechanism back down. Positive feedback occurs and
a person goes into a state of hypothermia and suffers heat stroke.
EFFECT OF OVER COOLING
If the core
temperature falls below 32oC the pulse rate weakens. The patient becomes
sluggish. This condition is called hypothermia.
VARIOUS WAYS MAMMALS ARE ADAPTED FOR COLD AND HOT CLIMATIC
CONDITIONS
Adaptation of human
beings in cold environment:
1. Presence
of hair In cold conditions hair erector muscles erect causing the still
hair to stand and collect air around them which acts as insulation for
heat loss
2. Possession of heat under epidermis: fat is a
bad conductor of heat, thus prevents heat loss
3. Ability
of narrowing skin blood capillaries: human beings constrict skin blood
capillaries; this reduces the amount of blood passing close to the skin.
This prevents heat loss by convection.
4. Ability to shiver:
During cold conditions human beings are able to perform involuntary
muscles contractions, shivering generate heat
Behavioural Adaptations
1. Wearing
of heavy black clothes: During cold conditions human being put on heavy
clothes, examples sweaters and coats. Heavy clothes create layer of air
between the body’s surface and the clothes. Trapped air is a bad
conductor of heat.
2. Use f heating systems in houses Human beings
during cold conditions use heating systems of different types to warm
houses so that they can make their living conditions comfortable.
Adaptations of human
beings in hot climate
1. Ability
of flattening of skin hair. During hot conditions human beings relax
hair erector muscles these cause body hair to lie flat on the body
surface and reduce insulation so that heat loss is affected
2. Ability
of widening the size of the skin blood vessels During hot conditions
human beings can enter a state of vasodilation where the skin blood
vessels near the skin surface expand. Vasodilation enables excess heat
to leave the body by radiation as a result of direct contact of vessels
with the skin
3. Possession of sweat glands Sweat glands secrete
sweat on the body’s surface through sweat pores. Excess heat is lost
when sweat evaporates
Behavioural Adaptation
1. Use of Shade: During hot conditions human
beings take cover in shade areas to avoid being over heated
2. Wearing of light-white clothes These reduce
absorption of heat during hot condition
3. Use of air conditioners Air conditioners
reduce excess heat in houses
Adaptations of a blue
whale in cold environment
1. Possession
of air Circular muscles near the body surface (between endothermic and
epidermis) Circular muscles near the body surface shunt the blood away
from the body surface during cold conditions then prevent heat loss by
convection
2. Possession of bladder (fat layer inside the
epidermis). Bladder acts as a thermal insulator. Bladder controls the
flow of heat from the body core to the body surface. The process occurs
during cold condition
Adaptation of blue
whale during warm condition
Possession
of circular muscles near the body surface (i.e. between endothermic and
bladder) where the animal is surrounded by warm sea circular muscles
open blood vessels near the body surface. This allows an animal to get
rid of excess body heat.
Adaptation of small
mammals e.g. squirrels and bats during cold condition
Adaptation of small
mammals e.g. squirrels and bats during cold condition.
During
cold conditions squirrels and some bats spend the winter in a state of
dormant state of hibernation in which they appear to be asleep and
during which no food is eaten
Hibernation
takes place in burrows. The temperature of these animals falls below
normal. The chemical activities in the body go very slow using food
stored as fat and glycogen.
Osmoregulation in Mammals
The Concept of
Osmoregulation
Explain the concept of
osmoregulation
Osmoregulation
is the maintenance of constant internal salt and water concentration in
an organism. OR It is the process by which the osmotic pressure of
blood and tissue fluid is kept constant.
Osmotic
pressure of blood and tissue fluid of an animal is exposed as the
depression of freezing point in relation to the habitat in which the
animal lives.
Factors which Affects
the Contents of Salt and Water in the Body
Mention factors which
affects the contents of salt and water in the body
Factors affecting
content of salt and water in the blood include:
· Amount
of water taken in the body Large intake of water causes blood to have
too much water while fewer intakes causes less water in the blood. It is
advised to take two liters equivalent to eight glasses of water per day
for the body to function properly. People who are very active might
need more than that.
· Climatic condition During hot weather
there is increased sweating which cause loss of water by evaporation
thus reduced amount of water in the blood. The vice versa occurs during
cold weather.
· Amount of salt taken into the body Putting
less salt in food causes reduced salt in the blood while putting too
much salt in food causes increased amounts of salt in the blood.
Moderate amounts of salt should be taken too much salt is not healthy as
it may lead to high blood pressure. Excess salts cause the kidney to
work harder as it is responsible for removing excess salts from the
body.
· Hormonal
Abnormalities: When less ADH is
produced it leads to increased content of water in the blood and vice versa.
· Blood sugar
regulation:
The hormones found in the pancreas in the Langerhans control regulation
of blood sugar in the body. These hormones are insulin and glucagon.
· Insulin hormone:This
is the hormone, which is produced from the B-cell. This hormone is
secreted when there is a large amount of blood sugar in the body.
Insulin promotes conversion of blood sugar into glycogen and stored in
the liver and skeletal muscles. Insulin forces the uptake of glucose by
body cells to produce energy.
· Glucagon hormone:
This is the hormone, which is secreted due to the lower level of
glucose in blood sugar. This Glucagon stimulates liver cells to release
glucose into the blood stream. Glucagon stimulates liver cells to
release glucose into the blood stream.Also Glucagon stimulates
absorption of glucose from the ileum.
Blood Sugar Regulation in
Mammals
The Mechanisms of
Regulating Sugar Level in the Blood
Explain the mechanisms
of regulating sugar level in t he blood
Blood
sugar regulation is the maintenance of a relatively constant blood
glucose level of the body. The end product of digestion of carbohydrate
is mainly simple sugars or glucose.
Glucose
is absorbed from the alimentary canal active transport into the blood
stream. Hence the blood sugar level in the blood rises to the extent
that regulation of it is necessary.
Blood
sugar in mammals is regulated using hormones, which are insulin and
Glucagon. These hormones are secreted by a specialized group of
pancreatic cells called islets of Langerhans. The alpha cells of the
islets of Langerhans secretes Glucagon while the beta cells secretes
Insulin.
When
the blood sugar level rises in the body insulin is secreted. The
insulin accelerates the entry of glucose into the liver and muscles to
be converted into Glycogen.
Glycogen is stored for
future use in the liver and muscles
Role of Glucagon in Blood Sugar Regulation
Glucagon
is secreted in response to a decline in blood sugar level in the blood
stream. Glucagon promotes the conversion of Glycogen to glucose and
inhibits the oxidation of glucose in the liver.
However
if the level of blood glucose is low, glucagon stimulates the
conversion of amino acids into glucose. The glucose formed is released
into the blood stream.
NOTE:Failure of a pancreas
to secrete insulin and glucagon results to a disease called Diabetes Mellitus
The Causes, Symptoms,
and Effects of High and Low Sugar Levels in the Blood
Outline the causes,
symptoms, and effects of high and low sugar levels in the blood
It’s important to
treat symptoms of high blood sugar right away to help prevent complications
Causes
Your blood sugar may
rise if you:
· Skip or forget yourinsulinororal
glucose-lowering medicine
· Eat too many grams of carbohydrates for the
amount ofinsulinyou took, or eat too many carbs in general
· Have an infection
· Are ill
· Are under stress
· Become inactive orexerciseless than usual
· Take part in strenuousphysical activity,
especially when your blood sugar levels are high andinsulinlevels are low
Symptoms
Early signs include:
· Increased thirst
· Headaches
· Trouble concentrating
· Blurredvision
· Frequent peeing
· Fatigue(weak, tired feeling)
· Weight loss
· Blood sugar more than 180 mg/dL
Effects
Ongoing high blood
sugar may cause:
· Vaginal andskininfections
· Slow-healing cuts and sores
· Worsevision
· Nerve damagecausing painful cold or
insensitive feet, loss ofhairon the lower extremities, orerectile dysfunction
· Stomachand intestinal problems such aschronic
constipationordiarrhea
· Damage to youreyes, blood vessels, orkidneys
Low Blood Sugar
Symptoms
Symptoms of low blood
sugar can occur suddenly. They include:
· blurry vision
· rapid heartbeat
· sudden mood changes
· sudden nervousness
· unexplained fatigue
· pale skin
· headache
· hunger
· shaking
· sweating
· difficulty sleeping
· skin tingling
· trouble thinking clearly or concentrating
· loss of consciousness
If
you have hypoglycemic unawareness, a condition in which you do not know
your blood sugar level is dropping, your blood sugar can drop so
quickly you may not even have warning symptoms. When this occurs, you
can faint, experience a seizure, or even go into a coma.
Very
low blood sugar is a medical emergency. If you know that someone is
diabetic and he or she is experiencing these symptoms, help him or her
to eat 15 grams of quickly digesting carbohydrate, such as:
· a half cup of juice or regular soda
· 1 tablespoon of honey
· 4 or 5 saltine crackers
· 3 or 4 pieces of hard candy or glucose tablets
· 1 tablespoon of sugar
Causes
Low blood sugar can
occur for a number of reasons. It is usually a side effect of diabetes
treatment.
Diabetes and Low Blood Sugar:Diabetes
affects your body’s ability to use insulin. Think of insulin as the key
that unlocks your cells, letting glucose in for energy. People with
diabetes use a variety of treatments to help their bodies use the
glucose in their blood. One very important treatment is insulin
injections.
If
you inject too much insulin, your blood sugar may drop too low. People
also sometimes inject insulin when planning to eat a big meal, but then
they do not eat enough.
Excess physical
activity without eating enough can also cause a drop in blood sugar levels.
Other Causes of Low
Blood Sugar
You don’t have to have
diabetes to experience low blood sugar. Some other causes of low blood sugar
include:
· certain medications, such as quinine
· drinking too much alcohol
· some medical conditions, such as hepatitis or
kidney disorders
· a tumor that produces excess insulin
· endocrine disorders, such as adrenal gland
deficiency
Effects
Mildly
low blood sugar levels are somewhat common for people with diabetes;
however, severely low blood sugar levels can be life-threatening. They
may lead to seizures and nervous system damage. Immediate treatment is
critical. It is important to learn to recognize your symptoms and treat
them fast. For people at risk of low blood sugar, having a glucagon kit,
a medication that raises blood sugar levels, is important. Talk to your
healthcare provider for more information.
BIOLOGY FORM
THREE TOPIC 6: REPRODUCTION
Concept of Reproduction
Reproduction
is the ability of living organisms to form new individuals of the same
species from those already in existence. Here, the new organisms replace
those that have died and so life continues. It can also be defined as
the process whereby organisms produce new individuals of the same
species. It is one of the important features of living things.
The Merits and
Demerits of Sexual and Asexual Reproduction
Explain the merits and
demerits of sexual and asexual reproduction
Sexual Reproduction
This
is a type of reproduction in which new organism is produced when a male
gamete fuses with a female gamete. Sexual reproduction involves the
fusion of two gametes. The process of fusion of gametes is called
fertilization.
These
two gametes differ in form and function and each is produced from a
different organ. In animals the gametes producing organs are called
gonads. These include the ovaries and testes. In flowering plant
structures concerned with the production of gametes are the ovaries and
anthers. The testes and anthers produce the male gametes while ovaries
produce the female gametes.
Merits of Sexual Reproduction
1. It ensures genetic stability
2. It ensures perpetuation of life
3. It brings variation
4. Leads to the interaction among organisms
Demerits of Sexual Reproduction
1. Offspring have a great chance of inheriting
diseases from the parent
2. The reproduction takes long time
3. It needs energy
4. The sexual reproduction produces few numbers
of offspring
5. It depends on presences of two parents
6. It leads to great chance of spreading diseases
7. It takes a long time until offspring are
produced
Asexual Reproduction
This
is the type of reproduction whereby production of offspring is from
single organism without the production of gametes. There is no fusion of
gametes.
Examples
of organisms who produce asexually are amoeba and bacteria. Asexual
reproduction involves only one individual organism. That means no change
of genetic material is passed from a parent to an offspring. The
offspring are also identical to their parents.
In this kind of
reproduction, in same organisms, body part such as roots, stems or leaves may
become reproductive body organs.
Depending on the type
of organisms asexual reproduction may be of different forms or ways such as:
· Fission
· Sporulation/Spore formation
· Budding
· Fragmentation
· Vegetative propagation
· Binnary Fission (Splitting)
· Suckers
· Bulbils
Binary Fission
(Splitting)
This is an asexual
reproduction in which an organism divides into two equal parts, which are
identical to each other.
Each part then grows
to attain the original size of the parent cell and hence become a separate and
independent organism.
Fragmentation
This
is a form of asexual reproduction in which organisms (parent) breaks
into two or more parts. Fragments grow and develop into a new organism
with identical features as the parent. Example worms such as Nematodes
and flat worms.
Sporulation/Spore
formation
Sporulation
is asexual reproduction by the use of spores. The spore develops from
single cell as a result of mitosis, forming a structure known as
sporangium. When the sporangium is truly developed, the wall bursts to
release the spores which when placed in suitable area they germinate
into new organisms.
Other organisms, which
reproduce by sporulation, are ferns and mosses.
Budding
Budding
is a type of asexual reproduction in which a new organism arises as an
outgrowth (bud) of the older organism (parent). The bud later separates
from the parent and grows to become an independent organism to attain
the size of the parent. Examples: yeast and hydra
Some
flowering plants reproduce through the formation of structure called
buds. Roots may form such buds, leaves or underground stems and such
buds sprout to form new independent plants.
Vegetative propagation
Vegetative
propagation is a form of asexual reproduction found in plants in which a
bud grows and develops into a new plant. The detached plant, root, stem
or leaves at some stages grows and develops into an independent plant.
Artificial vegetables propagation:
This is vegetative propagation, which occurs through man’s
manipulation. Man can learn from plants’ natural vegetative propagation
and can intervene and make propagation of plants artificially.
Natural vegetative propagation: Vegetative propagation involves different parts of plants as
discussed below. Such as:
Bulb
In this type each bud
grows to form a shoot, which produces a new bulb at the end of the growing
season.
Bulb is a modified underground
shoot having fresh strong leaves
Tubers
These
are short swollen underground storage organs formed from a stem or a
root. New tubers are made at the end of the growing season but do not
arise from old tubers.
Stem tubers
These
are short swollen underground stems, which store food, such as starch.
Normally, yam plants form a number of tubers each of which can rise to a
new plant. Such new plant continues to live after the death of the
parent.
Root tubers
These
are swollen adventitious underground roots. Roots tubers such as sweet
potatoes and cassava store their food in root tubers and do not bear
leaves or bud.
Rhizomes
These
are horizontally growing underground stems, bearing leaves, buds and
adventitious roots. Examples are lilies, ferns and grass.
Stolons
These
are slender stems, creeping horizontally as they grow along the ground
surface. Examples: strawberries, black currant and oxalis.
Suckers
These
are short horizontal branches, arising from the main stem or just below
ground level. Suckers contain food reserves. Examples: Bananas, sisal
and pineapples
Tap root
A taproot is the main
root that arises from a radical. Tap roots may become swollen and act as
storage organs.
Tillers
These
are collection of shoots. Grass plants consist of a number of tillers.
Each tiller has a number of leaves, which arise from the stem of nodes
at the base of the leaves.
Leaves
Some
plants such as cactus propagate vegetative using leaves. When the
leaves fall off from a plant they develop adventitious roots and buds,
which later may grow and develop into mature plants.
Merits of Asexual Reproduction
1. Asexual reproduction results into an
individual with the same genetic constitution as their parent.
2. Its offspring matures faster than sexually
reproduced organisms
3. It does not depend on processes of
pollination, seed or fruit dispersal
Demerits of Asexual Reproduction
1. Asexually reproducing organisms are at a great
risk to perish or get destructed when environmental conditions are unfavorable
2. The
parents may pass undesirable characteristics to the offspring since
only one individual organism is involved in asexual reproduction
3. Competition for resources such as food and
shelter may occur due to large number of organisms being produced
Meiosis and
Reproduction
The Meaning of Meiosis
Give the meaning of
meiosis
Reproduction
involves the transmission of genetic materials from one generation to
the next insuring that species survive. The process of reproduction
involves meiosis.
Meiosis is the type of
cell division, which occurs in the reproductive organs to produce sex cells known
as gametes.
In
this type of cell division the parent cells has diploid number of
chromosomes. However the daughter cell arising from the cell division
has the half number of chromosomes a condition known as haploid state.
Therefore meiosis
reduces the chromosomes number into half means from 2n to n.
The Significance of
Meiosis in Relation to Reproduction
Explain the
significance of meiosis in relation to reproduction
Meiosis
leads to the formation of reproductive cells (Gametes) such as ova and
sperms each with half number of chromosomes of the parent cells in
organisms reproducing through sexual reproduction.
It
involves the possibility of exchange of pieces of genetic information
between the paternal and maternal chromosomes of each pair leading to
new combination of characteristics in the gametes.
It
brings about variation when the members of each pair of chromosomes are
separated from each other independently (Random assortment)
Meiosis
leads to new combination of genes through the process of independent
assortment of chromosomes occurring during meiosis I
Meiosis
involves number of processes from prophase, metaphase, anaphase and
telephase. There are two meiotic divisions, the first and the second
division. All the above named processes occur in both the first meiotic
division and the second meiotic division.
First Meiotic Division
The first division of
meiosis consists of:
1. Prophase I
2. Metaphase I
3. Anaphase I
4. Telophase I
Telophase I
Prophase I
During prophase I the
following events occur.
· The nucleus disappears and the centrioles if
present migrate to the poles
· Chromosomes condenses and the spindle is
formed
· As
prophase proceed homologous chromosomes come to lie side by side and
there after become intertwined by the process called synapsis
Through
synapsis homologous chromosomes is referred to as crossing over. The
point at which homologous chromosomes exchange genetic materials is
known as chiasmata
Early Prophase I
The following events
occur during early prophase:
· Chromosomes contract, thickening, shortening
and become more visible
· Nucleus disintegrate and disappear
Mid Prophase I
· Homologous chromosomes come together
(synapses) forming a bivalent
Late Prophase I
· Chromatids cross over by chiasmata which
results into exchange of genetic materials
Metaphase I
· Bivalent homologous chromosomes moves to the
equator of the spindle
Anaphase I
· The two homologous chromosomes part company
and migrate to opposite poles of the spindle
· The centromeres of the homologous pairs
migrate towards the opposite poles where they are attracted.
Telophase
· The chromosomes reach their destination
· The spindle apparatuses breaks down and
disintegrates
· Then the nucleus membrane reforms around each
set of chromosomes
· The cell constricts across the membrane and
divides into two
Telephase I make the
end of the first meiotic division.
· At the end of this prophase the number of
chromosomes in each cell is half the chromosomes number cell.
· This is the reason why first meiotic division
is referred to as Reduction division
Second meiotic division
Prophase II
Centrioles replicates
and a new spindle apparatuses formed
Metaphase II
Chromosomes migrate to
the equator f the spindle
Anaphase II
· Sister chromatids part company and migrate to
opposite poles of the cell
Telophase II
· The spindle apparatuses disappears
· The nucleus repairs and a new nucleus membrane
is formed around each set of chromatids
· The chromatids uncoil and the cell divides
into two
· Chromosomes
regain their thread like structure and the cell enter interphase.
Meiosis results into the formation of four daughter cells each with
haploid set of chromosomes
· It should be stressed that the four
daughter cells formed has the half number of chromosomes present in the
original parent cell.
Experiments to Show
Stages of Meiosis Process
Carry out experiments
to show stages of meiosis process
Meiosis Vedeo
Reproduction in Flowering
Plants, the structure of the Flower
Some
plants use flowers to reproduce. The flowers contain all the parts
needed for the reproduction process. Sexual reproduction in flowering
plants takes place in the flower. Within a flower, there are usually
structures that produce both male gametes and female gametes.
The Structure of the
Flower
Describe the structure
of the flower
A
flowering plant is an angiosperm, which is any plant that produces a
flower or fruit. The sole purpose of the flower is to allow the plant to
reproduce. Each part of the flower plays a role in the steps of
reproduction. There are male gametes and female gametes. They are both
directly involved with sexual reproduction. Pollen may spread from plant
to plant but can only reproduce with the same species of plants. Let’s
take a look at the different parts of the flower.
Structure of a flower
STERILE PARTS
Let’s
start with the sterile parts of the flower, or those parts that are
neither male nor female. These sterile parts are not directly involved
in the fertilization process. Technically, a flowering plant can
reproduce without them; however, they do play important roles in helping
with reproduction.
· Pedicel:The
pedicel is a small stalk or stalk-like part bearing a single flower in
an inflorescence. The Some flowers have no stalk and are directly
attached to the stem of the plant.
· Receptacle:The
receptacle is the place on the stem where floral organs originate and
attach.It is the axis (stem) to which the floral organs are attached. In
most angiosperms, floral organs are attached in alternating successive
whorls. A whorl is an arrangement of sepals, petals, leaves, stipules or
branches that radiate from a single point and surround or wrap around
the stem.
· Sepals:Sepals are the parts
that look like little leaves that cover the flower before it blooms.
They cup the flower to protect it while it grows. Sepals are mostly
green and in most flowers they resemble leaves. A flower bud is
protected by sepals. Collectively, all of the sepals form the
calyx.Sepals may be hairy, for example in roses, or smooth, for example
in hibiscus.Some flowers have sepal-like structures beneath the calyx
known as epicalyx, for example the hibiscus flower.
· Petals:Petals
are the delicate and usually brightly coloured part that gives the
flower its character. Flowers have more than one petal, and the flower
petals are collectively called the corolla. The colour and scent
attracts the agents of pollination such as birds and insects. Fused
petals form a corolla that can be tubular or funnel-shaped as in the
flowers of sweet potato and pumpkin plants. Some of the petals of
leguminous plants are keel-like and they enclose stamens and
carpels.Sepals and petals are collectively referred to as the perianth.
Reproductive Parts of
the Flower
Identify reproductive
parts of the flower
The
flower is the reproductive unit of some plants (angiosperms). Parts of
the flower include petals, sepals, one or more carpels (the female
reproductive organs), and stamens (the male reproductive organs).
The female reproductive organs
The
pistil is the collective term for the carpel(s). A carpel is actually
three parts fused into one: stigma, style, and ovary. The stigma is at
the top of the flower. It is sticky to catch the pollen. Each carpel
includes an ovary (where the ovules are produced; ovules are the female
reproductive cells, the eggs), a style (a tube on top of the ovary), and
a stigma (which receives the pollen during fertilization).
The
ovary is at the base of the flower. From the ovary, extends a tubular
structure called the style and on the top of the style is a surface
receptive to pollen called the stigma. The stigma can take many
different forms, most of them designed to help trap pollen.
Female parts of a flower
The female parts of
the flower are discussed in detail below:
1. Ovary:The
ovary contains ovules. Ovules are unfertilized female gametes. The
position of the ovary in relation to the receptacle varies from one
flower to another. The ovary could be either superior or inferior in
relation to the position of the receptacle. A superior ovary is one that
is positioned above the receptacle, for example the ovary of a bean
flower. An inferior ovary is one that is positioned below or enclosed
within the receptacle. Examples are the ovaries of a rose and a black
jack flower.
2. Style:The style is a long
tube that attaches the stigma to the ovary. The length of the style
varies from one flower to another. This length determines the position
of the stigma. In the maize plants, the style and the stigma hand
outside the flower.
3. Stigma:The stigma
is a glandular sticky structure at the tip of the carpel. The stigma is
the tissue into which the pollen grains are deposited. The branches of
the stigma correspond to the number of carpels. Five branches of the
stigma indicate the presence of five carpels.
The male reproductive organs
The
male parts of a flower consist of one or more stamens. Stamens are the
male reproductive parts of flowers. A stamen consists of an anther
(which produces pollen) and a filament. The pollen consists of the male
reproductive cells; they fertilize ovules.
Male parts of a flower
The following is a
detailed description of the female parts of the flower.
1. Filament:The
filament is a slender stalk that supports the anther. The filament may
arise from the receptacle or the petals. It supports the anther.
2. Anther:The
anther is attached to the apex of the filament. It produces the pollen
grains that contain the sperm needed for fertilization.
Types of flowers
Flowers are classified
either as complete or incomplete. Complete
flowers have sepals, petals stamens and carpels. A flower with both
stamens and carpel is said to be bisexual. The hibiscus flower is
bisexual.
Incomplete
flowers lack some of the floral parts. Flowers that have carpels only
are referred to as pistillate flowers. Flowers that have stamens only
are referred to as staminate flowers.
Pollination
The Term Pollination
Explain the term
pollination
Pollination
is the transfer of pollen grains from the anthers to the stigma of a
flower. Pollen grains from the anthers are carried to the stigma by
wind, insects or birds. These are referred to as the agents of
pollination.Pollination, an important step in the reproduction of seed
plants, is the transfer of pollen grains (male gametes) from the male
reproductive organ to the female reproductive organ that contains the
ovule (female gamete) or transfers it to the ovule itself.
Pollination
is a very important part of the life cycle of a flowering plant. It is
part of the sexual reproduction process of flowering plants, which
results in seeds that will grow into new plants.
Types of Pollination
Identify types of
pollination
Pollination can either
be self or cross pollination:
1. Self pollination:This is the transfer of pollen grains from the
anthers to the stigma of the same flower.
2. Cross pollination:This is the transfer of pollen grains from the
anthers of the flower to the stigma of another flower of the same species.
Disadvantages of self pollination:A
potential drawback is that both gametes come from the same parent. If
the plant is well adapted to a stable environment, the production of
uniform offspring may be advantageous. However, inbreeding will result
and if there are disadvantageous recessive characteristics in the
parent, they are much more likely to be exposed than if the plant
cross-pollinates.
Advantages of cross pollination:Cross-pollination
is less reliable and more wasteful than self-pollination, but it is
genetically favourable because genes are transferred and variation
increases
Factors that favour cross pollination and hinder self
pollination
· Dioecious plants: Some plants have flowers that are only male
– they have onlystamen. Other plants of the
same species have flowers that are only female – they have only carpels.
· Monoecious plants:
Some flowers on a plant are only male; other flowers on the same plant
are only female. So, self pollination is avoided by a difference in the
timing of their development.
· Protandry: Anthers on some plants mature first.
Pollination of immature stigma on the same plant is therefore not possible.
· Protogyny: The stigmas mature first.
· Self-incompatibility: Pollination can occur but the pollen tube
doesn’t grow well, if at all, so no fertilisation takes place.
Agents of Pollination
Outline agents of
pollination
These
are organisms or physical conditions that facilitate transfer of pollen
grains from the anthers to stigmas. Plants, being immobile, normally
require agents for the transport of pollen, which are commonly wind,
insects, birds, mammals (bats, rodents, primates), and water. Insects
are the most common animals that will pollinate a carpel. The main
agents of pollination are wind, insects and birds.
Wind pollinated flowers
Wind-pollinated
flowers are also those flowers whose pollen is transferred by wind from
anthers to stigmas. Wind picks pollen grains from the anthers and
transfers them to the stigma.
Structure of a wind-pollinated flower:The
anthers and stigma of wind-pollinated flowers are exposed. This makes
sit easy for wind to blow the pollen that can then easily land on the
stigma. Flowers of grasses are a representative of wind pollinated
flowers.
Adaptations of wind-pollinated flowers
Flowers
that depend on wind for pollination are adapted in various ways. Plants
that are pollinated by wind have the following characteristics:
· Small
petals with exposed anthers and stigma. In some plants the petals are
often absent or have dull-coloured petals that do not attract insects or
birds. The petals and sepals are very similar in shape and size.
· Large
anthers which produce large amounts of pollen grains. Very large
quantities of pollen are produced to increase chances of pollination as
much will be lost while blown about.
· Anthers are loosely attached to the filaments
and hang freely to allow the anthers to be easily shaken by the wind.
· The
pollen grains are small, smooth, dry and light in weight and therefore
easily carried in the air by wind. Some pollen grains have bladder-like
structures that contain air, thus, increasing their buoyancy.
· Feathery stigmas with a large sticky surface
so they are more likely to catch pollen from the air.
· Large
and feathery stigmas, freely hanging out of the flowers, which provide a
large surface area on which the pollen grains can land. The stigma may
be branched or hairy to increase the surface area.
· Long, hairy style to expose the stigma outside
the flower.
· No nectar produced because they is no need to
attract pollinators to the flower.
· Not scented as the flowers do not attract
insects.
· Filaments grow long so stamens hang out of the
flower and shake in the wind to disperse pollen.
Wind-pollinated flower
Insect-pollinated flowers (bees, moths, butterflies)
Insect-pollinated
flowers are also referred to as entomophilous flower. The term
entomophilous is derived from the word entomophily- which means to be
carried by insects. Features of insect pollinated flowers include the
following:
· Large,
brightly-coloured petals which attract insects. Flower structure may be
adapted for one particular of insect, allowing them to land and feed.
· Usually scented; therefore they attract
insects to the flower.
· Nectarines
which contain nectar, for example, mango flowers have nectarines from
which bees collect nectar for making honey, and while doing so transfer
the pollen. The insects are guided to the nectarines by the nectar
guides.
· Sticky stigma that insects come into contact
with and
deposit pollen while collecting nectar. The pollen grains picked by
insects from other flowers stick onto the stigma.
· The stigma and
anthers are held firmly in position within the flower. This ensures
that when an insect lands on a flower, the stigma is not broken. The
stigma and anthers are located inside the flower where pollinators are
more likely to pick up pollen.
· The anthers are small in size and produce few
but large pollen grains.
· The
pollen grains are fairly large, heavy, sticky and with small spines.
This enables them to adhere to bodies of pollinators (insects or birds).
A bee collects pollen on its body as it feeds
Flower pollinated by birds:Birds
pollinate flowers when they search for nectar. Birds such as sunbirds
have long slender and slightly curved beaks that they use to probe into
the flower. Pollen grains stick on the beak. The pollen grains are
deposited on the stigma of another flower of the same species by the
bird as the bird feeds.
A bird feeding on nectar
Fertilization
The Concept of
Fertilization
Explain the concept of
fertilization
Fertilisation
is the union of the male and female gametes to form a zygote. Pollen
must fertilise an ovule to produce a viable seed. Fertilisation starts
when a pollen grain lands on the stigma. Only after pollination, when
pollen has landed on the stigma of a suitable flower of the same
species, can a chain of events happen that ends in the making of seeds.
After
a male’s pollen grains have landed on the stigma during fertilization,
pollen tubes develop within the style, burrowing down to the ovary,
where the sperm fertilizes an ovum (an egg cell), in the ovule. A pollen
tube emerges from the grain, its growth being controlled by the tube
nucleus at the tip of the tube. It may grow downwards in response to
chemicals made by the ovary (a response known as chemotropism).
In
a process called fertilisation, the two gametes join and their
chromosomes combine, so that the fertilised cell contains a normal
complement of chromosomes, with some from each parent flower. The
fertilised ovule goes on to form a seed, which contains a food store and
an embryo that will later grow into a new plant. The ovary develops
into a fruit to protect the seed. Some flowers, such as avocados, only
have one ovule in their ovary, so their fruit only has one seed. Many
flowers have lots of ovules in their ovary, so their fruit contains many
seeds.
There
are 2 types of seeds. Some are endospermic while others are
non-endospermic. In endospermic seeds the food reserve is the endosperm,
which is outside the plant embryo. Examples of this type of seed are
maize and wheat. Non-endospermic seeds have food reserve within the
cotyledon(s) of the plant embryo. This occurs in broad beans.
Process of
Fertilization in Flowering Plants
Explain process of
fertilization in flowering plants
During the growth and
extension of the tube, thegenerative nucleus, behind the tube nucleus, divides by mitosis to produce2 male haploid sperm
nuclei.
The pollen tube enters the ovule through the micropyle and penetrates
the embryo sac wall. Then, the tip of the tube bursts open, the tube
nucleus disintegrates, creating a passage for the male nuclei and what
follows is calleddouble fertilisation
· 1 male gamete fuses with the egg cell to
produce adiploid zygote which undergoes mitosis to form a diploid embryo.
· 1 male gamete fuses with both the polar nuclei
to produce thetriploid primary endosperm nucleus. The triploid nucleus undergoes mitosis to
form the endosperm.
The endosperm stores food materials that the embryo utilizes for growth and
during germination.
The process of fertilisation
Immediately after
fertilization the ovule becomes the seed and the ovary becomes the fruit.
This is what happens:
1. The zygote divides many times by mitosis to produce anembryo. It differentiates to become aplumule(young shoot),radicle(young root) and either 1 or 2cotyledons(seed leaves). It is attached to the wall of
the embryo sac by a suspensor.
2. The primary endosperm nucleus divides many times by mitosis to produceendosperm tissue.
In some seeds this endosperm is a food store for later use by the seed.
In others it may gradually disappear as the cotyledons develop.
3. To
accommodate all this growth the embryo sac expands and the nucellus is
crushed out of existence, giving its nutrients to the embryo and
endosperm.
4. The integuments surrounding the embryo sac
become the tough and protectivetesta (seed coat). The micropyle remains though so that oxygen and
water can be taken in during seed germination.
5. The water content of the seed decreases
drastically so the seed is prepared for dormancy.
6. The ovary wall becomes thepericarp–
the fruit wall, the whole ovary now being the fruit. The function of
the fruit is to protect the seeds and to aid in their dispersal, e.g. by
an animal. That is why they can be brightly coloured and sweet; animals
will eat them and scatter the seeds either at the time of eating or
when they are passed out of the gut in defecation, unharmed.
A detailed account of
what happens after fertilisation is given below:
· Formation of the
testa:The
testa is also referred to as the seed coat. The two integuments of the
embryo sac fuse to form one seed coat. The seed coat thickens and
hardens. Sometimes the outer integument forms the hard thick testa while
the inner integument remains thin and transparent. The thin transparent
inner integument is referred to as the tegmen.The testa protects the
seed against dehydration, physical damage and invasion by
microorganisms. The microphyle permits oxygen and water to enter the
seed during germination. The hilum is a scar on the testa that marks the
point of attachment to the fruit.
· The formation of the
embryo:The
egg cell nucleus fuses with the male nucleus to form a zygote. The
zygote undergoes mitosis to form the embryo. An embryo is a rudimentary
plant comprising the plumule, radicle and cotyledons.
· Formation of the
pericarp:The
ovary wall becomes thick and swells up with food substances. The
pericarp develops from the ovary wall. The pericarp is often the edible
layer in fruits. In mature fruit it may dry up or remain fleshy.
· Disintegration of the
floral parts:The
sepals, petals, stigma and style wither, dry up and fall off. In some
cases, some of the floral parts may become fleshy and form part of the
fruit. The fruit retains scars at the points of attachment to the
pedicel and style.
Reproduction in Mammals
The Male and Female
Reproductive Systems
Describe the male and
female reproductive systems
Female Reproductive
System
In humans, like
animals, female reproductive system is composed of:
1. Ovaries: Ovary is situated near each kidney.
Ovary produces ova, estrogen and progesterone as female sex hormones.
2. Fallopian tube: It is also known as egg tube/oviduct, it
is a funnel shaped opening. Fertilization normally takes place within this
tube.
3. Uterus:The
two fallopian tubes unite to form an expanded tubular organ called
uterus womb. It is there that fertilized ova implant and develop into an
embryo. N.B. Placenta is formed as an embryo develops, so as to allow
penetration of nutrients, gases (oxygen and carbon dioxide) and waste
products of metabolism An embryo receives nutrient and oxygen gases from
maternal blood circulation and give out waste product through placenta
into maternal blood system.
4. Vagina: This is
the posterior part of the female reproductive duct connecting the uterus
with the exterior. It is in this region that sperms are deposited. N.B.
Placenta with an endocrine at the last period of pregnancy, it secretes
progesterone like ovaries, which prevent production of ova and
contractions of the uterine walls.
Male Reproductive
System
The male mammal
reproductive system is composed of:
1. Testicles:
These are situated in a pouch of skin called scrotum. They produce
sperms as endocrine gland it produces secretes male sex hormone called
testosterone. Testosterone influences male secondary characteristics
during puberty in males.
2. Sperm duct: It Is
attached to each testicle, it acts as a temporary store for sperms. Each
epididymis leads into a duct called sperm duct or vas di deferens.
3. Vas deferens: Is the structure, which carries sperms
away from the epididymis to penis
4. Seminal vesicles and
prostate glands:These
are situated just below the urinary bladder and two structures called
seminal vesicles. Each seminal vesicle has a tube which leads to the
sperm duct. Around the junction of urinary bladder and urethra is a
gland called prostate gland
Gamete Formation and
Fertilization
The Process of Gamete
Formation in Mammals
Outline the process of
gamete formation in mammals
Gamete formation: Puberty
On
average, female attain puberty (Sexual Maturity) when they are 14 years
old and male when they are 16 years old. In both sexes, attainment of
puberty is accompanied by certain behavioral changes as well as
development of certain structures.
Those changes are
known as secondary sexual characteristics.
NB:
Puberty can be defined as the period when male/female changes from
childhood to adulthood. These changes are influenced by sex hormones
that are testosterone in males, progesterone and estrogen in females.
Secondary
characteristics in males:
· Hairs on their chins and pubic region
· Shoulders widen
· Voice deepens
· Pay more attention to female sex
Secondary
characteristics in females:
· Enlargement of the mammary gland and hips
· Deposition of fat which gives them more round
appearance
· Development of pubic hair
· Menstruation cycle
· Pay more attention to males (young men)
NB: At puberty sex
organs become fully functional in males and females.
Gamete formation:During
puberty stage is when both males and females are able to produce
fertile cells which united (of male and female) can cause pregnancy.
It
is believed that female gametes are produced before puberty but after
puberty is when they are fully matured and fertile while male gamete at
large are produced during and after puberty that is when can cause
pregnancy when united with female gamete.
The Processes of
Ovulation and Menstruation
Explain the processes
of ovulation and menstruation
Ovulation:
It refers to the release of ova/ovum from ovaries to the uterus. It is
expected to occur at the middle of the menstruation cycle.
Menstruation Cycle: This can be defined as the period between one and next menstrual
cycle (28 days)
Menstruation: This
is the discharge of mucus, epithelial cells and blood through vagina (3-5 days)
NB:
The menstruation and liberation of ova every 28 days alternates between
the two ovaries whereby in humans is called menstrual cycle and in
non-human mammals is called oestrus cycle.
The Process of
Fertilization Pregnancy and Child Birth
Explain the process of
fertilization pregnancy and child birth
The Menstrual Cycle
At the beginning of
the cycle, the menstruation can take place between 3-5 or 7th day from the first day. At this period the secretion of female
sex hormones are very low but increase after menstruation stops.
After
menstruation oestrogen secretion increases, follicle stimulating
hormone secreted to encourage production of ovarian follicle.
Luteinizing
hormone is for maturation and ovulation of follicle while oestrogen
prepares (thickening) the uterine for implantation when fertilization
takes place.
At the 14th
(middle) day is when ovulation can take place and secretion of
progesterone increases so as to thicken the uterine wall ready for
pregnancy.
NB: If no
fertilization occurs, the cycle starts again.
Placenta:This
is the portion of uterus, which is invaded by the villi and the
thickened portion of the chorion. The chorion like amnion is a thin
membrane but it has a thick portion called villi, finger-like
projection.
Umbilical Cord
· It connects the developing embryo to placenta
to the maternal blood system
· It carries two arteries and a vein of blood
circulation of an embryo
· AN
embryo uses umbilical cord for gas exchange, receiving nutrients and
removal of waste products via placenta into maternal blood system
Birth
· It
starts by a sudden fall in the level of oestrogen and progesterone
resulting in periodic contractions of muscular walls of the uterus which
cause pains called labour pains
· Under the influence of hormones a child is
given out through vagina
Copulation
· When
a male is sexually stimulated, the spongy penis is filled with blood
and becomes erect. The erect penis is inserted into the vagina and moved
back and forth, this movement stimulates sense organs in the penis and
ejaculation occurs.
· Ejaculation refers to the release of sperm
into the vagina; it can cause pregnancy when the fertile sperm unites
with fertile ova.
Fertilization:It
can be defined as the process of uniting male and female gametes to
form a zygote. The sperms remain alive for up to 48 hours while ova
remains alive for up to 36 hours.
Pregnancy:It
refers to the situation when a female conceives. That is fertilization
takes place to form zygote. Soon after zygote is formed its cell starts
to divide into many cells called embryo. It takes 3-5 days for the
zygote to reach to uterus for implantation.
Implantation:
· Refers to the process whereby an embryo
attaches itself to the uterine wall
· It takes 3 – 5 days to implant fully
· After implantation envelope is formed, the
outer chorion, inner amnion
· Between
these membranes of envelop there are fluids called chorionic fluids and
amniotic fluids respectively, both fluids act as shock absorbers,
protecting embryo from physical damage
Factors Which May
Hinder Fertilization
Outline factors which
may hinder fertilization
A
normal couple that is trying to start a family will usually be
successful after a few months. However, at least one in ten couples do
not conceive after a year or more of trying.
There are many reasons
why couples can’t produce children, some of them are:
· Ova are not released in normal monthly cycle
· The fallopian tubes may be blocked/twisted
· The women may make antibodies that destroy the
sperm
· The vas deferens may be blocked
· A high proportion of the sperm produced are
abnormal
· Very few sperms are produced in one
ejaculation
Ways of overcoming
these problems
· In – Vitro Fertilization (IVF)
· Fertility Drugs
· Artificial Insemination
The Concept of
Artificial Insemination and its Importance
Explain the concept of
artificial insemination and its importance
Artificial
insemination, also known as AI, is a procedure used to
treatinfertilitythat involves direct insertion of semen into a woman’s
womb. It is a process originally used on livestock that has been adapted
for human use. In human use, the sperm could originate from the woman’s
male partner, unless the male is infertile or there is no male partner
(i.e. single woman or woman in same sex relationship).
The
most commonly used method of artificial insemination, is IUI
(Intrauterine Insemination), as it has the best success rate. Other
types of AI are:
· IUTPI (Intrauterine tuboperitoneal
insemination
· ICI (Intracervical insemination)
· ITI (Intratubal insemination)
Artificial
insemination is beneficial to couples or individuals in many
circumstances. For example a couple may be producing healthy sperm and
eggs but not necessarily be able to have intercourse (maybe due to a
medical condition). Some other scenarios where artificial insemination
could be beneficial are listed below.
· A woman may want to raise a child alone – in this
case she would request a sperm donor to be artificially inseminated.
· The female may be infertile due tocervical factor
infertility–
the cervix is supposed to produce a mucus that helps sperm travel to
the womb. With cervical factor infertility, the cervix is either not
producing enough of this mucus, or it is producing mucus containing
sperm killing substances.
· The woman may be sufferingEndometriosis–
this is when cells from the womb lining start to grow in places they
should not within the woman’s reproductive system e.g. ovaries or
fallopian tubes. One of the possible results of this condition is
infertility. Artificial insemination can be successful in mild to
moderate cases of this.
· The female could have semen allergy –
this is rare but can still happen, due to certain proteins in the sperm
the woman may suffer an allergic reaction when the sperm makes contact.
With IUI most of the proteins would be removed before sperm insertion.
· The male is unable to produce enough sperm for
successful fertilization.
· The man is impotent(erectile dysfunction)– and would therefore be unable to perform
sexual intercourse.
· The
male could be infertile as a result of a medical treatment – some
treatments carry the risk of infertility e.g.radiotherapy. Before the
treatment the male would have been given the chance to freeze some of
his sperm.
· The couple could be in same sex relationship –
two
women who want to raise a child together would use sperm from a donor,
which one of the women would receive via artificial insemination.
· Reason
for infertility cannot be determined – IUI may be recommended to a
couple that cannot conceive even if no underlying reason for the
infertility can be identified.
Multiple Pregnancies
The Meaning of
Multiple Pregnancies
Give the meaning of
multiple pregnancies
Multiple
pregnancy refers to a situation when more than one ovum is released
into the reproductive tract of the female. On this occasion it is
possible for more than one ovum to be fertilized, consequently several
viable embryos may enter the uterus where they are implanted and
developed.
The Causes of Multiple
Pregnancies
Explain the causes of
multiple pregnancies
Multiple
pregnancies may occur naturally or arise as a result of reproductive
technology involving fertility drug or during an IVF program.
Causes of Multiple
Pregnancy Include:
1. More than one ovum released into the
reproductive track
2. One fertilized ovum splitting up into more
than one embryo resulting to twins
Difference between
Identical Twins and Fraternal Twins
Differentiate between
identical twins and fraternal twins
Identical Twins:These
are fully identical since they come from a single fertilized ovum,
which has split to give two or four embryos and developing to give
babies. They have the same sex and appearance.
Fraternal Twins:Resulting
when more than one ovum (ova) are released at a time and are
fertilized. They may have the same sex but not identical at all.
Disorders of Reproductive
System
Types of Disorders of
Human Reproductive System
Mention types of
disorders of human reproductive system
Reproductive
system is the one dealing with the birth of a child. We have two types
of reproductive systems, which are male reproductive system and female
reproductive system. The main function of reproductive system is to fuse
the gamete causing fertilization. Conserving the baby in a mother’s
womb till the day of bearing a child. Also is the one providing
birth/bearing of a child.
There
are many disorders that affect the reproductive system. These problems
may be found in both male and female reproductive systems. Disorders
affecting male reproductive system are Impotence, Premature Ejaculation,
Inflammation and Autoimmunity. Female disorders of the reproductive
system are Damage to the Oviducts (inflammation), Pelvic Inflammatory
Diseases (PID), Congenital Malformation and Functional Disorder.
The Causes and Effects
of the Reproductive System Disorders
Explain the causes and
effects of the reproductive system disorders
Male reproductive system disorders
Impotence
This
is the inability to achieve or maintain an erection of the penis. A
male could not erect the penis even though he will touch the sex organs.
Causes of Impotence
1. Impotence is usually psychological
disturbance. It may occur any time during the life time of a male
2. Strong alcohol consumption and use of drugs
3. Diseases also may cause impotence
Effects of Impotence
1. Impotence causes failure in performing the
social act, thus one cannot have children
2. May cause psychological disturbances to the
person
3. If an impotent person in married, impotence
may lead to the break of that marriage
4. It
may lead to the contamination of diseases such as HIV/AIDS, gonorrhea
when a couple get out of marriage to get sexual satisfaction
Premature Ejaculation
Premature
ejaculation is the situation where a man reaches orgasm before
penetration of the penis into the female track. Before inserting penis
into the female track the male ejaculated long time outside the female
track.
Causes of premature ejaculation
1. Fear, anxiety and sometimes is the first time
to have sexual intercourse
2. Psychological factors may also lead to a
problem
Effects of premature ejaculation
1. The person (male) fails to satisfy a woman
2. May lead to the breakage of marriage when a
woman finds another male for sexual satisfaction
3. May cause psychological disturbances in the
man’s mind
Autoimmunity
This
is a situation in which antibodies are made, which attacks own sperm,
thus reducing the number of sperms. It may lead to have small number of
sperms in the sperm store area.
Causes of Autoimmunity:Antibodies react to one’s own sperm. It is not exactly known
what causes autoimmunity.
Effects of Autoimmunity
1. It causes infertility to a person
2. May cause psychological effects to the person
who suffering from this problem
3. No more production of children
Inflammation
It is the condition in
which the urethra is blocked. It allows no movement of sperm out of the penis
and also the urine.
Causes of inflammation
1. May be caused by swelling of the prostate
gland
2. Also inflammation may cause the problem
Effects of inflammation
1. Inflammation may lead to sterility
(infertility)
2. May cause psychological problems to the person
3. May cause severe pain during sexual intercourse
as one/man wants to ejaculate but sperms fail to pass through urethra
DISORDERS OF THE FEMALE REPRODUCTIVE SYSTEM
DAMAGE OF THE OVIDUCTS (INFLAMMATION)
Oviduct of the female
may be blocked and causes the female organs to do fertilization of an ovum
Causes of damages to the Oviduct (inflammation):It
may be caused by the infections due to different diseases. The
infections may cause scarring, thus leading to partial or complete
blockage of the oviduct.
Effects of damage to the Oviduct (Inflammation):It
causes infertility to the female. A female may not have the ability to
carry/conceive a child due to failure of fertilization of an egg in the
fallopian tube.
PELVIC INFLAMMATORY DISORDER (PID)
This
is the pelvic infection caused by bacteria.This condition causes damage
to the oviducts.It occurs commonly to women with many sexual partners
and women who use the coil contraceptive method
Effects of PID:The condition may lead to infertility. A woman may fail to bear
a child and if she does so the child will not be normal
CONGENITAL MALFORMATION
Some women are born
with blocked oviduct or with no uterus (it mostly happens in very few cases)
Causes of malformation:This is a woman born with disorder caused by problems in the
reproductive system
FUNCTIONAL DISORDERS
This is a condition in
which a woman fails/unable to experience sexual pleasure during the sexual act
Causes of functional disorders
1. The cause may be psychological
2. Also may be biological one
Effects of functional disorders
1. May cause someone to stay away not conducting
sexual intercourse
2. May lead to end in marriage
Possible Remedies of
Reproductive System Disorder
Suggest possible
remedies of reproductive system disorder
Treatment of Impotence
1. If the causes of impotence are psychological,
counseling may help to cure it
2. If the cause is biological, one has to attend
hospital for medical check up
Treatment of premature ejaculation
1. Counseling is the most effective way to be
adopted to treat the problem
2. Medical treatment may be applied to stop the
problem
Treatment of Autoimmunity
This disorder is more
difficult to treat
Treatment of inflammation
One/man should have to
seek medical advice or intervention
Treatment of damage to the Oviduct (Inflammation)
Surgery is the most
effective way of treating this problem.
Treatment of PID
1. If a woman feels she has PID she should have
to go to the hospital for the right treatment
2. Abstaining from many sexual partners so as to
overcome more infections/problem
Treatmentof functional disorders
1. Counseling is the most effective way that may
be used to help the patient regain their confidence
2. Patients may go to the hospital for further checks
and treatment
Complication of the
Reproductive System
Types of Complications
of the Reproductive Systems
Mention types of
complications of the reproductive systems
Most
women give birth normally and perfectly but some problems can and do
occur in their reproductive system and causes effects to the newly
formed embryo.The problems/complications are abortion/miscarriage,
ectopic pregnancy and still births also breech birth.
1. Miscarriage:This
is the loss of a developing embryo before six months are over.
Medically, miscarriage is considered as the natural abortion. It may
result from foetus not being fully developed, failure of the embryo to
implant properly or due to deformed embryo.
2. Ectopic Pregnancy:Occasionally
the fertilized ovum fails to reach the uterus and instead implants else
where in the reproductive track. For example it can be implanted in the
fallopian tube instead of uterus. This situation is known as ectopic
pregnancy.Only 1 out of 50,000 ectopic pregnancies may be delivered
safely.
3. Abortion:Refers to the premature termination of
pregnancy. Abortion may occur naturally (miscarriage) or be induced.Induced Abortionis the abortion that is deliberately brought
out for medical reasons.Spontaneous Abortiois
the kind of abortion that occurs without humans or medical
intervention. That is not induced in any way. It is also referred to as
miscarriage.
4. Breech Birth:This is the situation
where a baby is born feet or buttocks first. In such cases, duration of
delivery is critical, too fast delivery may result in damage and too
long delivery may cause oxygen deprivation and if left for a longtime
may result to death of the baby.Sometimes it becomes necessary to remove
the baby by other means such as forceps (surgical tongs) or Caesarian
(C) section
5. Caesarian Delivery:This is the
removal of the baby from the uterus using surgical means through making
an incision in the abdominal and uterine wall. Caesarian delivery can be
done when either the baby is too big to pass the female reproductive
structures or the mother’s reproductive structures are too small.
Other
complications that occasionally arise during childbirth and generally
require management by an obstetrician may be described as follows:
· Non-progression
of labour (long-term contractions without adequate cervical dilation)
is generally treated with cervical prostaglandin gel or intravenous
synthetic oxytocin preparations. If this is ineffective Caesarian
section may be necessary.
· Fetal distress is the development of
signs of distress by the child. These may include rising or decreasing
heartbeat (monitored on cardiotocography). Shedding of meconium in the
amniotic fluid and other signs.
· Non-progression of expulsion
(the head or presenting parts are not delivered despite adequate
contractions); this can require interventions such as vacuum extraction
forceps extraction and Caesarian section.In the past a great many women
died during or shortly after childbirth but modern medical techniques
available in industrialized countries have greatly reduced this totally.
· Unanticipated heavy
bleedingduring
or after childbirth is potentially lethal n places without immediate
access to high-level emergency care. Heavy blood loss leads to
hypovolemic shock, insufficient perfusion of vital organs and death if
not rapidly treated by stemming the blood loss and blood transfusion.
Causes of
Complications of the Reproductive System
Outline causes of
complications of the reproductive system
Other
complications that occasionally arise during childbirth and generally
require management by an obstetrician may be described as follows:
· Non-progression
of labour (long-term contractions without adequate cervical dilation)
is generally treated with cervical prostaglandin gel or intravenous
synthetic oxytocin preparations. If this is ineffective Caesarian
section may be necessary.
· Fetal distress is the development of
signs of distress by the child. These may include rising or decreasing
heartbeat (monitored on cardiotocography). Shedding of meconium in the
amniotic fluid and other signs.
· Non-progression of expulsion
(the head or presenting parts are not delivered despite adequate
contractions); this can require interventions such as vacuum extraction
forceps extraction and Caesarian section.In the past a great many women
died during or shortly after childbirth but modern medical techniques
available in industrialized countries have greatly reduced this totally.
· Unanticipated heavy bleedingduring
or after childbirth is potentially lethal n places without immediate
access to high-level emergency care. Heavy blood loss leads to
hypovolemic shock, insufficient perfusion of vital organs and death if
not rapidly treated by stemming the blood loss and blood transfusion.
Ways to Minimize the
Occurrence of Complications and Disorders of the Reproductive System
Suggest ways to
minimize the occurrence of complications and disorders of the reproductive
system
The following are the
way of minimizing occurrence of complications and disorders of the reproductive
system.
1. Stop/minimizing
amount of alcohol that we take/drink may keep us away from impotence
and other infections that may lead to disorders in reproductive systems
2. Practicing
different duties/activities and participating in exercises also sports
and games helps to reduce psychological problems which may lead to
disorders in the reproductive system
3. Medical check up between
the partners who want to get married to know their Rhesus factors, blood
groups, infections and HIV/AIDS in order to minimize the death or
miscarriage during pregnancy
4. Getting early treatment of any
infections like gonorrhea, syphilis, bilharziasis, which may cause
damage to the fallopian tubes and urethra in male and female.
Sexuality and Sexual
Health and Responsible Sexual Behaviour
The Concept of
Sexuality
Explain the concept of
sexuality
Sexuality includes
fondness or readiness for or interest in a sexual activity.
Sexuality is the
function of whole personality begins at birth and end at death it includes:
1. How you feel about yourself as a person
2. How you feel being a man or woman
3. How you get along with member of the same or
opposite sex
4. It also includes genital and reproductive
processes such as intercourse and child bearing
Social Cultural
Factors Influencing Sexual Behaviour in Different Age Groups of People
Mention social
cultural factors influencing sexual behaviour in different age groups of people
Sexual Behaviour in Children
Factors influence
sexual behavior in Children:
1. Start at infantry when children shown their
own bodies
2. Also sexuality is shown at early age (play
age)
3. Children also do and learn from their fellow
children on different sexual matters
4. Education – in school and community
5. Initiation rites
6. Religious beliefs
7. Mass Media
8. Economic status – both poor and rich
Sexual Behaviour in Adolescents
Factors influence
sexual behaviour in adolescents:
1. Early marriage
2. Social pressure (tradition of being
independent)
3. Drug addiction – it can stimulate or depress
the sexual practice
4. Peer pressure
5. Education – school and community
6. Moral decay
7. Marriage breakdown and problems
8. Poverty
9. Mass Media
10. Lack of proper guidance and counseling
Difference Between
Responsible and Irresponsible Sexual Behaviour and Their Impact on Oneself
Family and Community
Differentiate
responsible from irresponsible sexual behaviour and their impact on oneself
family and community
Responsible
sexual behaviours are the behaviours, which are acceptable in the
societies to elicit or trigger sexual activity like marriage.
Irresponsible
sexual behaviors are those behaviours of an individual, which are not
acceptable by family as well as societies, example use of alcohol and
drugs (drug addiction) and prostitution to trigger sexual activities.
Effects of irresponsible Sexual Behaviour
To an individual:
· Becoming pregnant at a tender age, thus losing
the opportunity of being officially married or continuing with studies
· Being in danger of contracting fatal venereal
disease such as syphilis, HIV/AIDS, gonorrhea etc.
· It may lead to death, when an individual tries
to abort an unwanted pregnancy
· Getting a responsibility of caring for a
family at an early age
· It
can degrade the personality of a person. For example prostitutes or
rapists have no place to put their faces in some societies
To family
· Breakage of marriage
· Lead to conflict in the family or marriage
· Loss of particular relative if he/she
contracts disease like HIV/AIDS
Ways of Eradicating
Irresponsible Sexual Behaviours/Practices in the Family and Community
Suggest ways of
eradicating irresponsible sexual behaviours/ practices in the family and
community
There
are several measures that can be taken to eradicate irresponsible
sexual behaviours in the family and community. The measures include the
following:
· Old children should not sleep with young
children on the same bed without strict follow-up by the parents/guardians.
· Keeping
out of all situations culminating to sexual arousal such as watching
pornographic movies, alcoholism, meeting in isolated places, attending
night clubs and accompanying ill groups of people like homosexuals,
harlots, and rapists.
· Adults, guardians, parents, and teachers
should talk openly to children about relationships and sexual-education
matters to make them informed about the aftermath of irresponsible
sexual behaviours.
· Close supervision and guidance of children
· Getting
involved in age-appropriate activities (for example, sports, boys/girls
clubs, after-school activities, and craft activities) to help keep
one’s minds out of sexual mood and desires.
· Protection for
children from scary or traumatic events, including media coverage of
such events as wars, bombings, or shootings; and
· Closely observing what your child watches on
television and in the movies or is exposed to in music and on the Internet.
· Following religious teachings on sexuality.
Appropriate Life
Skills Required to Cope with Adolescent Sexuality and Sexual Behaviour
Mention appropriate
life skills required to cope with adolescent sexuality and sexual behaviour
Life
skills are behaviours that enable individuals to adapt to and deal
effectively with the demands and challenges of life. There are many such
skills, but core life skills include the ability to:
· make decisions, solve problems, and think
critically and creatively;
· clarify and analyze values;
· communicate ( including listen, build empathy,
be assertive, and negotiate);
· cope with emotions and stress; and
· feel empathy (understand and care about other
peoples’ needs, desires and feelings) with others and be self-aware.
Some life skills
required to cope with adolescent sexuality and sexual behaviour include the
following:
· Educating
youth about health-related issues, such as alcohol, tobacco, and other
drug use; nutrition; reproductive health; and preventing HIV/AIDS and
other sexually transmitted infections (STIs). Life skills education can
also be effective in preventing school dropout and violence among young
people.
· Referring young women to age-appropriate
reproductive health services.
· Promoting youth’s livelihood through
vocational training, recreation, etc.
· Mobilizing
and empowering individuals, families, and communities in order to
reach, influence, and involve everyone to become a part of the solution.
· Parents and teachers strictly supervising
teenagers at home and school, respectively.
· Adults and parents inculcating good moral
behaviours to adolescents by serving as good examples for them to follow.
Family Planning and
Contraception
The Concept of Family
Planning and Contraception
Explain the concept of
family planning and contraception
Family planning is a decision made by a person freely on how many children
he or se may want to have and when she or he wants to stop.
Contraception
refers to prevention of conception that is prevention or preventing the
fusion of the male gamete with the female gamete. Birth control is
broad it includes measures taken to prevent birth after fertilization.
There are two methods
used namely Artificial family planning methods and Natural family planning
menthods.
1. Artificial Family
Planning Methodsincludes
sterilization, oral contraceptives, intra-uterine devices, Norplant, diaphragm
and condoms
2. Natural Family
Planning Methodsincludes rhythm, the
basal body temperature and withdrawal (coitus interrupt)
Social Practices which
Enhance Family Planning
State social practices
which enhance family planning
Social cultural
practices, which enhance family planning, include the natural methods of family
planning, which are:
Abstinence
This
refers to the avoidance of sexual intercourse or can be defined as
refusal by sexually active male and female to have sexual intercourse.
Advantage of Abstinence
1. It is the most effective method of preventing
conception
2. The approximated rate of failure of this
method is zero percent
Disadvantages of Abstinence
It is said to be
unrealistic for many to practice this method
Rhythm Method (Calendar Method)
This
is modified from abstinence. N intercourse is done during the fertile
period. These days can be counted or identified by counting the days
between menstrual period and also by observing certain associated
physical changes such as small changes in body temperature. A woman may
also keep a written chart of her menstrual cycle for certain months and
is taught how to determine the number of days each month when sexual
intercourse must be avoided. Total abstinence is about 7 days in a
month.
Advantages of the Rhythm Method
1. The method is said to be natural and widely
acceptable
2. It has no cost
3. It is said to be 77-87% effective
Disadvantages of Rhythm Method
1. The approximate failure rate is 20%
2. It requires good knowledge and good record
keeping
3. It also requires a period of abstinence
4. Irregularity of the menstrual period (cycle)
Temperature Method
This
method is based on the changes of a woman’s body’s temperature due to
her menstrual cycle. The temperature is said to drop during the
menstrual period and remains low until the release of an ovum. A rise in
temperature is noted at ovulation and sexual intercourse should be
avoided at this time if conception is not intended.
Advantages of the Temperature Method
1. The method is said to be 76-80% effective
2. It costs nothing
3. It does not require fitting and regular
checkups
Disadvantages of the Temperature Method
1. The approximate failure is said to be 20-24%
2. Sperms released to a female tract a few day
before ovulation may survive until ovulation
3. Irregularity of the ovulation may cause
fluctuation of temperature
Billing Method (Ovulation Method)
This
method is based on the fact that the secretion from the female tract
changes noticeably during the course of her menstrual cycle. The
appearance of clear thin mucus in female tract secretions at ovulation
is noted and sexual intercourse is avoided during these times.
Advantages of Billing Method
1. It is said to be 76-80% effective
2. It costs nothing (it is cheap)
3. It does not require fitting and regular check
ups
Disadvantages of Billing Method
Regularity of
ovulation may cause fluctuation of temperature
Coitus Interruption (withdrawal)
Coitus
interruption or withdrawal is another natural method of birth control
in which a male withdraws his penis from a female tract before
ejaculation. This method is one of the oldest methods of birth control.
Coitus interruption requires unusual degree of will power.
Advantages of Withdrawal
1. The method is costless
2. It is reliable for 76-80% when practiced
Disadvantages of Withdrawal
1. The method requires some degree of will power
2. It has a high failure rate in case fluid
released from the penis just before ejaculation may contain viable sperms
3. Sperms may leak from penis before is
withdrawal even without ejaculation
Artificial Methods of birth control
Barrier Methods
These methods prevent
sperms from entering the female tract. These methods include:
Condom:This
is a thin rubber sheath, which prevents sperms from entering into the
female tract. Male condom is worn over an erect penis during intercourse
and prevents sperms from being released into the female tract that way
preventing union of sperm and ovum.
Advantages of Condoms
1. Condoms are said to be 85% to 93% reliable
when used properly (handled with care)
2. They may help prevention of sexually
transmitted diseases such as fungal infection
3. They are cheap and easily and obtained
Disadvantages of Condoms
1. Condoms can tear and leak. In such cases they
become useless
2. A condom may slip off the penis after climax
3. Condoms may disrupt the act of love making
(reduce sensation)
Female Condoms
Female condoms are
equivalent to male condoms in that:
· It is a thin rubber tube with a close end
which fits inside the female tract
· Female
condoms are relatively new, so not much is known about them. They give a
woman some control and are said to have the advantages as those f the
male condoms
Diaphragm
This
is another barrier method that prevents entering of sperms into the
female tract.A diaphragm is a flexible rubber, which fits over the
cervix and prevents entry of sperm to uterus. It is applied with
contraceptive jelly (cream) or spermicidal chemicals, which kill sperms.
A doctor must prescribe this method.
Advantages of Diaphragm
1. The method is said to be cheap
2. It can be inserted a few hours before sexual
act
Disadvantages of Diaphragm
1. The diaphragm must be fitted by a doctor and
training is required for the woman to fit it
2. It disrupts spontaneity
3. It occasionally causes pain in the abdomen
4. It needs check up after every six (6) months
5. It should be left in place six hours after
intercourse
Spermicidal
These
are chemicals, which kills sperms. Spermicidal foam, or spermicidal
jelly is placed in an applicator, which is inserted and emptied into the
female tract just before sexual intercourse. These kill sperm and block
cervix.
Advantages of Spermicidal
1. It is cheap
2. It is effective for about an hour
Disadvantages of Spermicidal
1. It is messy
2. It has a high failure rate if used on its own
The pill
This
is one of the most widely used contraceptive methods.The pill is an
oral contraceptive by synthetic oestrogen and progesterone taken daily
by the female.It function by suppressing the normal release of
gonadotropins from the pituitary. These synthetic hormones prevent the
ovulation process, thus hindering fertilization.
Advantages of the pill
1. The pill is said to be very effective i.e. it
is about 98% successful
2. A woman has control over the method
3. It has no interference with sexual intercourse
Disadvantages of the pill
1. It is not suitable for all women. There may be
increased risk of blood clotting in some women
2. It is not recommended for older women or women
who smoke
3. Short term side effects of the pill include
nausea, weight gain, tissue swelling, fluid retention and minor headaches
The Importance of Male
Involvement in Family Planning
Outline the importance
of male involvement in family planning
People go for family
planning or control for a number of reasons. Among these are:
1. To
ensure both partners are healthy and observe medical measures that are
advised, giving enough time for a mother’s full recovery after giving
birth
2. Ability to cater for the needs of many
children
3. Couples decide to practice child spacing so
that they can cater for their needs
4. Helps
to improve the health of a mother by helping women to avoid pregnancy
at early age, unwanted pregnancies and to become pregnant at late age of
35 years
Importance of Family Planning and Contraception
1. Some family planning methods help to prevent
the transmission of HIV and sexually transmitted infections
2. Family planning reduces the need for unsafe
abortion
3. Family planning reinforces people’s rights to
determine the number and spacing of their children
4. Family planning helps to build the health of a
mother
5. Family planning enables the couple to be able
to handle the family by catering to the needs of family
Maternal and Child Care
The Concept of
Maternal and Child Care
Explain the concept of
maternal and child care
A
pregnant mother needs a lot of care and consideration for the best of
her health and that of the child. Basically there are two types of care
given to pregnant mother. These are pre-natal and post-natal care. The
care given before birth is called pre-natal care and the care given
during birth is called natal care. But a pregnant mother also needs a
care and support after birth of the child; this kind of care and support
provided after birth is called post-natal care.
Maternal care during pregnancy (Pre-natal care)
Pre-natal care means
before birth; therefore pre-natal care means a care given to a pregnant woman
before delivery.
Things to be done by a pregnant mother
· Visit ante-natal clinic for counseling
· Maintain general body cleanliness all the time
· Have enough rest
· Wear lose-fitting dresses and low heeled shoes
for comfort
· Eat well balanced diet containing all types of
food
Things to be avoided by a pregnant mother
· Doing tiresome and manual work. Example
lifting heavy loads
· Taking any medicine not prescribed by the
doctor
· Taking drugs such as alcohol, cigarettes which
could be detrimental to the unborn baby
· Tight clothes and high heeled shoes
· Avoid
situations leading to chances of contracting venereal diseases such as
gonorrhea, syphilis and AIDS which might affect the baby
· Avoid stressful situation
Care during natal period
Natal
period is the period when the pregnant mother gives birth to the child
she has been carrying in her womb for about nine months. A number of
things need to be considered during natal period:
· An
expectant mother needs to undergo labor under supervision of a trained
nurse or trained birth attendant whenever this is possible
· If
any complications occur that can not be solved by either a trained nurse
or a trained birth attendant arises, an expectant mother should be
referred to the health center or hospital for medical assistance
· Most
births are perfectly normal but problems can and do occur. When
problems arise, modern delivery facilities or techniques such as
Caesarean section and vacuum extraction are used. Care should be taken
not to damage any organ of the baby or the mother
· In case a
newborn baby is pre-mature appropriate services should be given to it so
as to help it accomplish a normal pattern of growth and development
Post-natal services to the mother and the child
These
are care and services provided to the mother and the newborn child
after birth. After birth a mother has another big responsibility and
role of breast-feeding the child.
Also
a mother should attend post-natal clinic for medical checks and
immunization of the child Balanced diet should be supplied to a
lactating mother so as to ensure that she gets enough nutrition for her
benefit and ultimately that of the child.
Proper
nutrition will help her to restore the tissue worn out during the natal
period. This helps also the newborn baby to have enough milk from its
mother. The health of both the mother and her child should be seriously
taken care of.
Child health care
Mothers should
breast-feed the child whenever possible, mother’s milk is better than any other
food because of the following:
1. It contains antibodies that are much needed to
the child
2. In case the mother has no health problems such
milk is free from contamination
3. Mother’s milk also contains much proteins and
vitamins which are very important for the child’s growth
4. Breast
milk is easily digested than other milk example bottled milk. Therefore
children who take milk from their mother rarely suffer from
constipation
5. Mother’s milk is said to contain some
chemicals which help in development of the nervous system of the child
6. Regular
attendance of post-natal clinic for the child is very important. The
child should also get immunized against different infections and
diseases such as polio, measles and other diseases
7. The mother
should follow medical advice on how to handle the child and in case of
any problems report it to the personnel concerned
Social-Cultural
Factors which Affect Maternal and Child Care in the Family and Community
Mention
social-cultural factors which affect material and child care in the family and
community
These include the
following:
· Female Genital
Mutilation (FGM):This
is the practice of circumcising women. It is said to have effects
during childbirth. It causes women to experience pain, bleeding, and
shock and may lead to infection.
· Local Belief:These
are certain local beliefs and taboos such as banning women to eat
certain types of foods such as protein rich foods, which could help to
build their health and that of the child.
· Working
especially hard work such as cultivation: Hard work may cause several
problems to the pregnant woman such as miscarriage or pain.
· Alcohol Consumption
during pregnancy:In
most cultural practices taking alcohol is considered as a normal
behaviour. But alcohol during pregnancy affects both the health of the
mother and that of the child.
Appropriate Ways of
Providing Maternal and Child Care for People Living with HIV/AIDS (PLWHA
Suggest appropriate
ways of providing maternal and child care for people living with HIV/AIDS
(PLWHA)
These include the
following:
1. To ensure frequent medical check up for both
maternal and child
2. To ensure they get well balanced diet
3. Avoid sharing sharp objects like razor blades
4. Counseling in order to help them deal with
their feelings of loss and grief
5. To avoid discrimination for people living with
HIV/AIDS
6. Ensure the use of polite language when
providing care to them
7. Wearing of gloves when cleaning their bodies
and clothes
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