Mwl Marco

COORDINATION
Coordination means is the linking together of the function of different organs so that they work at the time and the rate required by the body.

- The linking together in time and space of the organs and their activities

In the organism there are many organs. Each organ has a special function (e.g. ear, eye, heart, stomach, brain, hand, etc.) as if they are independent of each other. All there organs need to be connected with each other by the exchange of substances.

Therefore, coordination is the reception and assembling of sensory information in a central location and subsequent response of organism.

Importance of coordination

Without proper coordination the bodily activities would be thrown in chaos and disorder. 

Therefore coordination is important in the following ways

i  It enables an organism to detect changes in the environments

ii  It enable the organism to protect themselves from danger or enemies through the use of sense or organs eg lion using eyes

iii Helps communication for effective functioning of particular cells, tissue, organs or the whole organism and survival of the organism.

iv. It helps in controlling growth and development of the organisms

v.helps the organism to work in harmony, e.g. increase of breathing rate and heart beat during exercise or work, alternation between swallowing food and inhaling air

HOW COORDINATION IS BROUGHT ABOUT.

-In animals Co-ordination is brought about by the nervous system and the endocrine (hormonal) system.

-In plants it is under the control of hormone, e.g. in the meristem a chemical called auxin effects the growth of the plant.

NERVOUS SYSTEM IN HUMAN
The nervous system involves five main components.

Fig. Human nervous system

1. STIMULUS (nerve impulses).Is the changes in the external or internal environment of the body .eg. liht, touch, sound

2. RECEPTORS.is the part of animal’s body which detects the changes in the environment eyes ears, nose, skin and tongue.

3. Coordinator. Is the organ which receives messages as sensory nerves impulses from receptors

4. Effectors. Is an organ which receives motor nerve impulses from the central nervous systems and bring about the appropriate responses

5. Responses is the physiological muscular or behavioural activity that is done by an organisms under the influences of stimulus (is the body activities that provoked by the stimulus).

       NEURONES

Neurone is an elongated branched cell that is the fundament unit of the nervous system being specialized for conduction of the impulses. Is  units that make up the nervous system. The system runs through out the body. Through irritability the organism detect and respond to stimuli from the internal and external environment

External environment

Examples are heat, light, sound, pressure, gravity, chemicals, water, food, and other living organisms.

Internal environment

   Eg are Water, glucose, minerals and temperature.

Types of stimuli (1) physical e.g touch (2) chemical e.g. chemical substances (3) biological.eg predators

 BASIC PROPERIES OF NEURONES

• Excitability-It is highly capable of responding to stimulus
• Conductivity- It is highly of conductivity messages(nerves impulse) along i

STRUCTURE NEURONES

Neurones like other animal cells consist s the following structures

i.Cell body-cell body in which the most cells content are confined to one region.

                   -It is nucleated part of the nerve cells

ii.Dendrites-These are short numerous fibres which receives impulses and conduct them   towards the cell body.

iii.Dendron-Is single long fibre.

                    -When present it receives nerve impulse from the dendrites and conduct them

                       toward the cell body                      

iv.cytoplasm- contains the nucleus and other organelles

v. Axon-is the single long fibre

              -It insulated by the tissue called Myelin Sheath

               -The myelin sheath insulating tissue is secreted bySchwan cells which surrounding   the fibre

               - carry nerve impulse away from cell body

vi. Node of Ranvier-These are contrictions which interrupt the myelin sheath at th

                                  millimetre interval It help to propagate the nerve impulse and speed up the transmission of the nerve impulse

                                -            

- Many projections arise from the cell body. The longer projection is called AXON   and shorter projection is called DENDRITES.

Axon- and Dendrites- Conduct impulse toward the cell body.

FUNCTION OF NEURONES

1.Convert stimulus into the environment into electrical,chemical messege called impulse

2. Transmit impulse to otherspecilazed cells called effectors, which produce the appropriate responses.

 TYPES OF NUERONES(Nerve cells)

There are three types of neurones

i.  Sensory neurones

ii.    Motor neurones

iii.  Relay neurones.

1.SENSORY NEURONES (AFFERENT)

These involves the transmit impulse toward the brain and from receptor. It link the sensory cells to the central nervous system.

-They have cell body located at the middle with th axon pojcting from either side.

           

Fig.The structure of sensory(afferent) neurone

 2.RELAY NEURONES

These are the nerves that connect the sensory nerves and motor nerves with other  and with other nerves cellsthrough small gaps or neurojunction called Synapse.

-They found in the brain and spinl cord.

-The terminal part of the  dendron of a relay neurones receives impulse from the terminal part of the axon of a sensory neurones

             

 

3.      M0TOR NEURONES

These are responsible to carries impulse from brain or from the spinal cord to an effectors organ causing a change to take it

-Its cell body is located at one end of the axon

-Terminal part of its axon is situated in an effect orgab such as muscles



The synapse (neural function)
Is a junction between dendrites of two adjacent neurones through which nerve impulse is passed from one neurone to another.

Neurone, muscular junction, ie. contact between muscle fibre & dendrites of motor neurones.

Nerve impulse: slight  electric charge which travel along the neurone. It can not be reversed. It can travel at a speed of 30m/s or 180 km/hr.

Importance of synapse

1.      Enable single neurone to have connection with many other neurones from different parts of the body.   eg. Touching hot thing= i. Remove hand quickly, ii. Jumping up, iii. Crying or loud sound.

2.      Ensure transmission of  impulse in one direction

3.      play important role in learning & memory

Fig.Direction of nerve impulse

Types of nervous system.
-Central nervous system (CNS)

-Peripheral nervous system (PNS)

-Autonomic nervous system (ANS).

1.Central nervous system (CNS)

Is a concentrated mass of nerves which make up 

(1) brain 

(2) spinal cord.

All impulses from or to the body pass through the CNS. So it is the centre of cross connection and linkages

.

(I). The brain.

Is the enlarged front end of the spinal cord in vertebrates. The brain is housed in a system of membranes called meninges and it is encased in a bony structure called skull or cranium. The nerves arising from the brain are called cranial nerves.

Parts of the brain.

a) FORE BRAIN(Cerebrum.)

This is the anterior portion of the brain. It is composed the Olfactory lobes and Cerebrum. The outer portion is grey hence called grey matter, like inner part is whitish hence called white matter.

The cerebrum interlinks impulses and coordinates response. Nerve impulses from the eye, ears and tongues are interpreted in the cerebrum.

Also cerebrum is responsible for speech, reasoning, memory, decision making, behavior and imagination.

Also controls activities are under the control of such as running, walking, eating, and playing. Since such activities are under the control of the will of the animal, they said to be voluntary or consciously done. In human the cerebrum is extremely active, compared with other animals. That is why we can reason and recall past experience.

The olfactory lobes receive impulses of smell via olfactory nerves from the organ that sense smell (nose).

Functions of the cerebrum
i.It is involved in learning imagination and creativity
ii.It is responsible for reasoning and intelligence
iii.It is responsible for personality or character
iv.It controls voluntary body movements such as walking and dancing
v.It involves for sight, hearing. taste and smell and speech
vi.It is the memory centre

b). MID BRAIN
Mid brain is smaller compared to other regions. This part of the brain is called the OPTIC LOBES. It lies between the fore brain and the hind brain. It is composed of thalamus and hypothalamus together with pituitary gland.
Functions

• To relay information between fore brain and hind brain.                    
• Also to relay information between fore brain and the eyes. It is in this region that optic nerve linking the brain and eyes originates.

c) HIND BRAIN

Hind brain is composed of the cerebellum and medulla Oblongata           

  1. Cerebellum
  - The cerebellum regulates and coordinates body, posture, movements which are concerned with equilibrium

    - Receive impulses from skeletal muscles, tendons and the inner ear, then relayed to fore brain                                                                                      

i.In the fore brain the impulses are analyzed and the animal is made aware of its posture. 

ii Also cerebellum relays impulses from the inner ear to the appropriate muscles. These muscles act in such a way that the body position is changed to maintain balance.

 The medulla Oblongata: Is the most posterior part of the brain which merges with the spinal cord 

iii. It controls all unconscious activities of the body e.g. Breathing, heartbeat, digestion, dilation and contraction of blood vessels, secretion of juices from glands and temperature regulation 

ordination centre. 

It controls learned movement like walking, posture, speech and balance.

The hypothalamus;

Is part of vertebral fore brain which concerned with regulating physiological state of the body like, body temperatures, chemical composition of the body, osmoregulation, metabolic functions and some involuntary activities like appetite, sleep, water excretion. It also influence the release of hormones by the pituitary gland.

-Olfactory lobes deals with smell, and optic lobes deals with sight

Functions of the brain

-Receives impulse from all the sensory organs of the body.

-Sends off motor nerve impulse to the effectors (glands & muscles) causing them to function accordingly.

-Correlates the various stimuli from different sense organs.

-Co-ordinate body activities so that the mechanism and chemical reactions of the body work efficiently together.

-It stores information so that behaviour can be modified according to the past experienced.

  

2. THE SPINAL CORD

The spinal cord is the extension of the central nervous system (CNS) from the brain to the tail. The spinal cord is incased in meninges and protected by the vertebral column. The spinal cord is made up of 2 halves fused together called spinal canal, the canal is filled with cerebrospinal fluid.

The spinal cord gives rise to 31 parts of spinal nerves which exist between the bones of the vertebral column and connect to all parts of the body.

 The spinal cord serves as nerve impulse conduction path way. Nerve impulses transmitted by the spinal nerves are relayed to the brain. Then from the brain to the spinal cord, then transmitted to the effector organs

•  The spinal cord serves as nerve impulse conduction path way. Nerve impulses transmitted by the spinal nerves are relayed to the brain. Then from the brain to the spinal cord, then transmitted to the effector organs .
•  Spinal cord act as a coordinating centre. It controls actions called involuntary actions, these are actions which are fast and automatic. They cannot be controlled by the will power and need not to be learnt. Such responses are called reflex actions e.g. sneezing, coughing. 

STRUCTURE OF SPINAL CORD 

 

     

GREY MATTER

•  Is central part of spinal cold 
•  It consists the central canal filled with cerebrospinal fluid 
•  It consists of relay neurons which connect information between the afferent and efferent.
•  The cell body is found inside the grey matter

WHITE MATTER

Is the outer part of the spinal cord, consist of axon of sensory and motor neurons

 

VENTRAL ROOT

This is a part of the spinal which carries motor nerve fibres

 DORSAL ROOT

This is a part of the spinal which carries sensory nerve fibres

 

Function of the spinal cord

a. Conducts sensory nerve impulses from the receptors of the sense organs to the brain.

 b.Conduct motor nerve impulses from the brain to the effectors. 

c Enables animals to  attain an upright position through the maintenance of muscles tone.

 Functions of spinal cord:

-Conducts sensory nerve impulse from receptors to the brain.

-Conducts motor nerve impulse from the brain to the receptors.

-Enables animals to attain an upright posture through the maintenance of muscle tone

Protection of nervous system

The nervous system is very delicate and vital to the well being of the animals, it is therefore highly protected from damage

•  The brain is protected from mechanical damage by the bones which make up cranium /skull. 
• The meninges are tough membrane that protect the brain from shock. 
•  The cerebrospinal fluid provides a floating environment. 
•  The fluid also helps to protect the brain from blows on the skull and from abrupt head movement. 
•  The spinal cord is protected by the vertebrae from mechanical damage. 
•  The nerves are sheathed by membrane. 

PERIPHERAL NERVOUS SYSTEM

The peripheral nervous system is made up of sensory and motor nerves. These nerves run to and from the central nervous system and the rest of the body.

REFLEX ACTION

A reflex action is a sudden, automatic and uncontrolled response of parts of the body or the whole body to external stimuli. E.g. - when a hot object is accidentally touched, the hand is quickly withdrawn

OR

Is rapid automatic involuntary response to a stimuli by an organ or a group of organs, e.g. withdrawal of hand from a hot object, sneezing in case of a foreign body in the nose, blinking of the eye in case an object passes close to it, secretion of tears when the onion is cut, swallowing, enlargement of pupil in different light intensity
Reflection action involves the nervous system.The stimulus initiates nerve impulse in sensory neurones.The impulses pass via a relay neurone in the spinal cord and motor neurone to the effector,a muscle or gland, which brings about the response.The neural pathway linking a receptor and an effector organ is known as reflex arc.

Reflex arc of a hand being withdraw from a hot water

Reflex arc

Is the rout /path followed by the nerve impulse during a reflex action. The arc composed of

1.      Receptor cells

2.      Sensory neurone

3.      Relay neurone

4.      Motor neurone

5.      Effectors, i.e. muscles in glands
Usualy there are neurones connecting the reflex arc with the brain.These connections make it possible for brain to be aware of the reflex action and sometimes override them.For example, when a cook picks up of a very hot pot from stove, the natural things to do is to drop it (reflex action). However, knowing the valuable contents in the pot, the brain, through its neutral connection via the spinal cord, will prevent the cook from dropping the pot

Types of reflex actioni.      Simple reflex action (instinctive Reflex action).
Is a rapid automatic in voluntary response to a stimulus, by an organ or system of organs.Which does not involve the brain directly for its initiation, e.g  dilation / contraction of iris in changing light without being aware, sneezing, withdrawal of hand from hot object, tears when onion is cut.

-Nothing can be done to prevent it or modify it.

ii.   Conditioned reflex action:

Is an automatic response which can be evoked from an animal by a related stimulus substituted for the one which usually initiates the response eg. Dog salivate normally when it sees food (related stimuli); but repeated bell(unrelated stimuli) before food can condition dog to salivate.

Condition reflex action is formed from the past experience and invokes modification of

behaviour throw learning .

Pavlov experiment( Ivan Pavlov – Russian  physiologist) did on 1902.

Usually dog salivates in the sight, smell & test of food. In experiment Pavlov rang bell immediately before giving food to the dog. The dog leant to associate the sound of the bell with food, (associative learning). He continued for several weeks. Later on he  rang the bell but did not present the food, and found that the sound of the bell initiated salivation in the dog.

In human beings conditional reflexes are used in riding a bicycle, driving, swimming, walking, writing, etc.

Differences;

Simple reflex action	Conditional reflex action
Inborn response to external stimuli	Learned / modified patterns of behaviours gained through experience
Same in all members of the species	Different in members of the species
Initiated by a related stimuli	Initiated by unrelated stimuli substituted for the one which usually initiates the response.
Single stimuli brings about response	Combined ( related & unrelated ) stimuli, when the pattern is repeated brings  about response
Does not involve the brain directly	Involves brain directly

Function of reflex action
Protect the body against the injury
QN. Explain briefly what happen in the body of magogwa when the hand touch the hot 
object.
Answer.
On touching a very hot object, the temperature and pain receptors in the skin, of hand stimulated.Nerve impulses are initiated in the nerve ending in the receptors.The impulse are relayed to the spinal cord through a sensory neurones. Within the spinal cord, the nerve impulses are passed on a relay neurones across a synapse, then the nerve impulses are passed on to a motor neurone. Once the nerve impulse are in the motor neurone they are transmitted to the biceps muscles.on reaching the biceps muscles the nerve impulses initiate a contraction of these muscles.When the muscles contract they pull the hand away from the hot object.

AUTONOMIC NERVOUS SYSTEM

They control involuntary activities of the body, e.g. gut movements, heart beat, secretion of glands.

The nerves which comprise the autonomic nervous system arise from the brain or from the spinal cord and innervate which the body has a little or no voluntary control.

They are two types (i)sympathetic and (ii)parasympathetic system.

The two systems normally oppose each other in their functions on the same organ.

Parasympathetic	sympathetic
Slow heart beat	Accelerate heart beat.
Dilates arterioles	Contracts arterioles.
Contracts bronchioles	Dilates bronchioles
Contracts iris	Dilates iris.
Speed up gut movement	Slow gut movement (peristalsis)
Relax bladder & anal sphincter	Contracts bladder & anal sphincter
Relax erector pili muscles	Contract erector pili muscles
Decreases sweat secretion.	Increases sweat secretion

SENSE ORGANS

A sense organ is a mass of specialised sensory receptor cells compacted together, eg. Eye, ear, skin, tongue, nose, and hypothalamus that detect blood sugar level.

The sensory receptors are composed of specialised cells that detect stimuli acting on the animal’s environment. Usually a sense organ or cell can respond to only one kind of stimulus, eg. Cell sensitive to touch will not be affected by stimulus of heat.

Strong stimulus produces more sensation than weak stimulus because,

i.      It stimulate greater number of sense organs or cells.

ii.    Some sensory cells respond only when stimuli is strong or intense.

Types of receptors.
Interoreceptors: Are located within the body and respond to stimuli from within the body, Example, osmoreceptors, ie. Hypothalamus.

Exterorecptors: Are located near the body surface and respond to stimuli from the external environment, eg. Photo receptors.

Kinds of receptor cells.

-Photoreceptors, are sensitive to light.

-Mechanoreceptors, are sensitive to pressure and vibration.

-Thermoreceptors, are sensitive to temperature.

-Chemoreceptors, are sensitive to chemical substances.

-Osmoreceptors, are sensitive to osmotic pressure and changes of body fluids.

-Painreceptors, are sensitive to pain  on the surface and in the body.

SENSORY ADAPTATION

When the sensory nerve in the receptor is stimulated for the fact first time, transmission of nerve impulses is very fast, continued stimulation soon leads to a slowing down of impulse transmission and finally it cease all together.

The sensory adaptation is useful for the comfortable life of an organism

E.g. when a person is cut or bruised, they feel sharp pains to begin with. These pains have not healed yet.

Sensation

Sensation arise in the brain. Sensory organ or cell receive the stimulus and sends the impulse to the brain. The brain record the message and we recognise it as sensation. The impulse is responded to by a reflex or it is transferred to the sensory region of the brain.

1.THE SKIN
The mammalian skin consists of two main layers, the epidermis and the dermis 

 The dermis carries several types of sensory receptor cells and nerve endings. Certain parts of the body have more sense cells than others., eg. The finger tips have more touch receptors than other skin parts, the skin of the lower arm has many heat and cold receptor cells.

A particular sense cell responds only to one kind of stimulus, this gives the name to the sense cell, ie. Pain receptor.

Skin receptors are more complex consisting of nerve endings surrounded by a connective tissue called encapsulated nerve endings. These protect the nerve endings form mechanical damage and also help in generation of nerve impulse.

The receptor cells and their encapsulated nerve endings.

1.      Pressure receptors (Pacinian corpuscles), that detect pressure and respond to pressure. It also enables us to use tools skilfully.

2.      Pain receptors (Ruffini’s end organ), that detect and respond to pain. It is very important in the survival of animals, ie. Avoid destruction from whatever is causing pain.

3.      Touch receptors (Meissner’s Corpuscles), that detect and respond to touch. Is found in non-hairy skin, eg. Finger tip and tongue; also is connected to the hair erector muscles.

4.      Thermoreceptors, that detect temperature change, there two kinds

i.        Heat receptors (End bulls corpuscles), that respond to heat.

ii.      Cold receptors (Krausser’s end organs), that respond to cold.

The thermoreceptors detect change of up to 0. 5 ⁰C.

.

Fig. type of receptors

2.TONGUE
The sensation of taste is detected by group of cells called Taste Buds. In mammals taste buds are found in Lingual papillae, that is upper surface of the tongue. In other vertebrates taste buds are distributed on the walls of buccal cavity. Taste buds are also called Gustatory cells.

The combined activity of taste buds and smell receptors gives the sensation of flavour. The sensation of taste helps the animal to distinguish between suitable and unsuitable substances for ingestion. Also stimulate salivary glands and stomach walls to secrete enzymes.

Fig.Human tongue

Types of  Taste Sensation

1.      Sweet: at the tip of the tongue

2.      Sour: at the sides of the tongue

3.      Bitter: at the back of the tongue

4.      Salt: all over the tongue.

Mechanism of tasting

A chemical dissolves on the moisture of the tongue and stimulate sense cell which transmit impulse to the brain. The brain identifies the particular sensation (Taste).

3.THE NOSE
Smell detectors or receptors are located in the nasal cavity (nose). Smell cells are grouped together to form Olfactory epithelium. The cells are stimulated only by chemical substances which have dissolved in moisture (mucus) on the olfactory region. Impulse from sensory cells is transmitted via Olfactory nerve to the Olfactory lobe of the brain. Here the impulse is interpreted as smell.

QUESTION 

Why hot food often has more taste than cold food? 

-  This is because they vaporize more, the vapour passes from the mouth up into the nasal passages where it stimulates smell receptors. 

Why we cannot taste foods small when suffering from cold? 

- This is because the nasal passages are inflamed and coated with mucus. The smell receptors are essentially non- functional. 

  

4.THE EAR

The Ear has two functions

-Hearing: detection of sound waves and vibrations in the air.

-Balance: provides information on the animal’s position in space, ie. Is the animal upright or at an angle and hence make necessary adjustment.

Parts of the Ear.

Fig. Structure of the mammalian ear

The ear has three parts, Outer ear, Middle ear and Inner ear.

1.      The Outer Ear

The outer ear is the air filled part of the ear which consists of:-

i.           Pinna: is a funnel shaped made of skin and cartilage. It trap sound waves and directs to the ear tube. Some animals like cattle are able to rotate their pinna to locate direction of sound waves.

ii.         Ear tube (External auditory canal): is a tube through which sound waves travel. The canal  have lots of hairs and secretes wax which traps dusts and other dirty particles and micro organisms from entering the ear. It directs sound waves into the ear drum.

iii.       Ear drum (Tympanum): is a thin membrane that forms boundary between the outer and the middle ear. It vibrates when hit by sound waves and transmit it to the ear ossicles.

2.      The middle ear.

Is an air filled cavity in the skull. It is composed of three tiny bones called ear ossicles, which link the ear drum with the oval window of the inner ear.

i. The three ossicles are:      a. Malleus or Hammer

b. Incus or Anvil

c. Stapes or Stirrup

The three ossicles transmit sound vibrations from the ear drum to the oval window. When the ear drum vibrates it causes the ossicles to move forward and back wards. The Malleus transfer vibration from ear drum to Incus which pass it to Stapes which then transmits the vibration to oval window

ii. The middle ear is connected to the pharynx (The mouth and nose cavity) by a tube called Eustachian tube. The tube is normally closed but opens in case of swallowing or yawning. It opens to let air enter or leave the middle ear, this equilizes the pressure between inside and outside of the ear drum and by that it prevent the ear drum from bursting.

iii. Oval window: is a membrane which passes on vibrations in the fluids of Cochlea.

3.      The Inner Ear.

The inner part consist of series of fluid filled chambers, like:-

a.       Cochlea: is a coiled tube filled with a liquid called Endolymph. Cochlea contain sensory cells connected to the brain by Auditory nerve. The part that respond to sound is called the Organ of Corti. Cochlea detect sound vibration..

b.      Semi circular canals: are three canals which stand at right angle to each other. At one end of each canal a welling called ampulla contain sensory cells to detect motion. The movement of the fluid in the canals (by rotating, nodding or moving our head) stimulate sensory cells of the ampullae. The impulse sent to the brain is interpreted and the response by which we automatically keep our balance.

c.       Utriculus and Sacculus (Utricle and Saccule): are special structures at the base of semi circular canals which have the sensory hair cells to detect gravity.

.

Mechanism of hearing

The pinna collects sound waves and directs them to the eardrum through the ear canal. When sound waves hit the eardrum it vibrates. These vibrations are transmitted trhough the ear ossicles and amplified. The vibration of the stape causes the membrane at the oval

window to vibrate. The vibrations of the oval window are transmitted to the perilymph  and then spread to endolymp..The vibration of endolymph on sensory cells is induce the nerve impulse in the sensory fibres.These impulse are transmitted to the brain for interpretation. for interpretation

Qualities of sounds

1.      Loudness: Is the magnitude or intensity of the sound. It is determined by amplitude or strength of the sound waves striking ear drum. Loud sounds will cause a large displacement while soft sounds will cause a small displacement of basilar membrane found in the cochlea.

2.      Pitch: is the tone of the sound. Is determined by the frequency of the sound wave. Sound of low frequencies have long wavelengths, which cause low tones. Sounds of high frequencies have short wave lengths, which cause high tones.

Human ear is sensitive to vibration ranging from those of very low note about 20to 30000 vibration per second

SENSE OF ACCELERETION

The semi- circular canals are concerned with the detection of motion. The ampullae of the semi – circular canals contain sensory cells, attached to sensory nerve endings. The sensory cells have hair which is enclosed in a core of jelly substance called “cupulla”.

Whenever the body or the heart moves the semi – circular canals lags in its motion and apparently moves in the opposite direction.

The moving fluids cause the cupulla to tilt thus pressing the hair of the sensory cells. The pressing of the sensory hair creates nerve impulses in the sensory nerve endings. The nerve impulses are transmitted to the brain. The brain then interprets direction and speed of motion of the body or head

 

SENSE OF EQUILIBRIUM

The utriculus and sacculus are concerned with sense of balance and posture. The inner surface of these structures contains sensory cells. The sensory hair cell, which has protruding hairs embedded in a jelly – like substance containing tiny particles of chalk called “otoliths”.

When the head is titled on one side the otoliths move in the opposite direction pulling or pressing the sensory hairs they initiate nerve impulses which transmitted to the brain. Then the brain directs the angle which tends to return the body to its normal.

 

HEARING DEFECTS

Loss of hearing and deafness can be caused by

1. BLOCKAGE OF THE EAR CANAL: Production of too much wax may harden and block the external auditory canal. 

2. RAPTURE OF THE EARDRUM: The eardrum may be perforated or burst due to load, noise, physical blow and infection.

 3. FUSSION OF THE EAR OSSICLES: Due to abnormal growth of connective tissues in the middle ears which fuses the ear ossicles and prevents them from vibrating.

 4. NERVE DESTRUCTION: This is caused by either the damage of the auditory nerve due to nervous disease

.Ear disorders

Proper hearing depends on the efficient transmission of sound waves from the external ear through middle ear to inner ear and the response of the sensory cells. Any interference with these will result to certain degree of deafness.

Hearing defects.

Loss of hearing and deafness can be caused by:-

a.       Blockage of the Ear tube by too much wax or foreign bodies

b.      Rapture (perforation) of Ear drum, The burst of ear drum due to physical blow, loud noise or infections, ie. When children stick sharp object in the ears.

c.       Fusion of the Ear ossicles: caused by abnormal growth of connective tissues in the middle ear which fuses the ear ossicles together and prevent them from moving.

d.      Nerve destruction: caused by damage of auditory nerve due to nervous diseases, over dose of antibiotics, accidents, or exposure to loud sounds.

Disease of the Ear.

a.  Acute Labyrinthitis: Is an inflammation of the middle ear and cochlea. It may lead to deafness if not treated. Can be treated by using drugs.

b. Tinnitus: caused by accumulation of wax in the ear or use of certain drugs, eg. Quinine. Treatment is by removal of wax and abstaining from causative drugs.

c.   Vertigo: caused by disorientation of body in space. This is due to dilation of endolymph.

5.SENSE OF VISION (EYE)

Receptors which are concerned with the sense of vision are located in the eyes.

Front view of mammalian eye

   From the front view, the eye has three well marked regions

Pupil – These is a small dark central portion which is surrounding by the region called Iris.                                                           

Sclerotic layer – Is the layer which surrounds the iris. This is the largest part of the eyeball.                                                           

Cornea: is a transparent region in front of the eyeball passes over the iris and pupil.

Fig.The cross-section through mammalian eye

  Function and adaptation of the parts of the eye.

The eyeball has a cavity which is divided into two portions:

(i)           Eye lids.

-Two thin folds of the skin in-front of the eye ball. 

-They protect external surface of the eye. By blinking (movement of the eye lids) 

-they keep the surface of the eyes moist. Saline liquid (solution of Sodium Chloride and Hydrogen Carbonate) from the tear gland( below the upper eyelid) contains an enzyme which kills micro organisms. 

-Blinking washes this liquid across the eyeball.

(ii)         Eye lashes:

Many long hair s on the edge of the eye lids. They protect the eye from entries of small particles.

(iii)       Eye brows: the raised potion of the skin above the eyeball, thickly covered with hair. -They prevent the entry of dust particles and sweat in the eye.

(iv)       Sclera: (sclerotic layer). The outer most layer of the eye. Is white in colour and is formed of tough non- elastic connective tissue to protect and maintain the shape of the eye.

(v)         Tear glands: (lachrymal glands): 

-they are under the top eye lid. 

-They secrete tears which keep the surface of the eye ball moist and wipe away the dust and other foreign materials when blinking. 

• -They also contain Lysozyme. An enzyme that kills bacteria. Excess tears drain through the lachrymal duct and released through the nasal cavity.

(vi)       Cornea: is the transparent front part of the eye (is the continuation of the sclera). 

It refracts or bends light rays.

(vii)     Conjunctiva: Is a transparent membrane (epithelium) which cover and protect the cornea.

(viii)   Choroid: Is a heavily pigmented layer beneath the sclera.

- It contains blood vessels to supply the eye with oxygen and nutrients. 

It has black pigment to absorb scattered light. Thus reducing reflection of light within the inner eye. 

Choroid extends to the front of the eye to form ciliary body and iris.

(ix)       Ciliary body: Are the elastic muscles (containing blood vessels) which relax and contract changing the shape of the lens. 

This allows vertebrate to focus both near and distance objects i.e. accommodation.

(x)         Iris: A pigmented circular and radial muscles which regulate the amount of light entering the inner eye by changing the size of the pupil. 

This adaptation help adjust the iris to vision in bright and dim light. The iris determine the colour of the eye.

(xi)       Pupil: Is a hole or opening of the iris which allows light to enter the eye.

(xii)     Lens: Is a transparent biconvex structure filled with jelly like substance.

- It is held in place by suspensory ligament. 

The lens help the eye to focus for the different substances(near or far), a process called accommodation.

(xiii)   Suspensory ligaments: Are fibers which hold the lens in position by attaching it to the ciliary muscles.

(xiv)   Retina: Is the inner most part of the eye that contain light sensitive cells (photoreceptors)

. It has two types of cells: cones and rods.

(a) cones: sensitive to white colour and function in bright light. 

It contains iodopsin, adapted for bright light and colour vision.

(b) rods: sensitive in black colour and function in dim light. It contains rhodopsin, adapted for low illumination and does not perceive colours. Cones are less sensitive than rods.

(xv)     Fovea: special region of the Retina with the highest concentration of cones, where most of the light is focused, and is the point of best seeing. Is also called Yellow Spot.

(xvi)   Blind Spot: A spot in the retina where all sensory neurones enter the optic nerve. Here are no sensory cells (no cones or rods). So image falling on the blind spot can not be perceived by the brain (no image or picture can be made.)

(xvii) Optic nerve: The nerve consists of many sensory neurones transmitting nerve impulse from the retina to the brain.

(xviii)    Anterior chamber: Is the space between cornea and lens. It contains watery fluid called aqueous humour which supply nutrients and oxygen to the lens and the cornea.

(xix)   Posterior chamber: Is the space between the lens and the retina. It contains jelly like transparent material called vitreous humour, which maintain the round shape of the eye. 

(xx)     Eye muscles: Are attached to the sclera and the bony orbit. Their contractions serve to rotate the eye ball in various directions.

Comparison between mammalian eye and camera

Mammalian eye	Camera	Function
Iris	Diaphragm	Regulates amount of light.
Lens	Convex lens	Focuses light.
Retina	Sensitive film	Formation of image.
Lens changes in Thickness	Lens move back and forward	accommodation (adjustment to different for focuses)
Choroid	Black surface	Prevents internal reflection of light.

 

IMAGE FORMATION

Vision depends upon image formation. The formation of an image is dependent upon cone of the proper of light. That is when light passes through from one medium to another its velocity changes. If light goes from air into a denser medium the rays bent. This bending of light is called Refraction.

   The formation of image depends on the law of refraction. Light rays from the object enter the eye through the cornea. Then they pass through the aqueous humour, pupil, lens, vitreous humour and finally reach the retina where the image is recorded as real upside down and smaller than the objects.

 When light rays fall on the retina, they stimulate the photo receptor and impulses are sent to the brain through the optic nerve. The cerebrum then interprets the impulses, making the object visible. The interpretation also means that a person will be able to see the object in its right orientation and correct size 

Mechanism of image formation (Seeing)
When light rays pass from one medium to another of different densities are bent. Light rays from external objects enter the eye; they pass through cornea, aqueous humour, pupil, lens, vitreous humour and finally to the fovea centralis of the retina, where the image is recorded as real, upside down, smaller than the object. All these media have different densities and refract light rays focusing them on the fovea centralis of the retina.

The inverted image (upside down and smaller) on the retina stimulates receptor cells and nerve impulse is transmitted to the right and left eye, the brain receives the impression of different distances. The brain gives a sensation of object’s nature, colour, brightness, distance and direction. In our impression the objects ‘’Seem to be upright’’

    

ACCOMODATION OF THE EYE

Accommodation is the ability of the eye to focus, both near and distant objects or ability of the eye to produce clear images of objects at different by altering the focal length of the eye lens. This is brought about by action of the ciliary muscles, and elastic of the lens.

When the eye is focusing on a distant object the Ciliary body muscle relaxes, while the suspensory ligaments become tighter and pull on the lens. The lens gets thinner and gives you clear image of the object.

When the eye is focusing on a near object the tension of the suspensory ligament is relaxed or decreased and the lens becomes thick and more convex. This allows light rays to be focused into the retina.

 

THE COMMON EYE DEFECTS 

Defects of the mammalian eye are structure deviations of the eye which alter the focusing mechanism of the eye.

There are two common eye defects

1. HYPERMETROPIA (long sight) 

2. MYOPIA (short sight)

1. HYPERMETROPIA (long sight)

This condition is due to compression of the eyeball, resulting in the shorting of the normal distance between the lens and the retina.

In this condition, light rays from distance object are focused on retina, where light rays from near objects fall behind the retina.

This means;

•  A person cannot see near objects clearly 
•  Images of near objects fall behind the retina.
•  Caused by the eyeball being too short or the lens being too thin, so that it does not converge the light rays enough. 
•  These defects are corrected by using spectacles with convex lens. 
•  Convex lens converge the light rays before they reach the eye.

2. MYOPIA

A short sighted person focus distance objects properly. This individual can only focus near objects clearly. This is because the light rays of distance object converge at a point infront of the retina.
This may be due to eyeball being too large. This may be corrected by a biconcave lens. This help to diverge the light rays from distance objects so that they can be focused on the retina.

COLOUR VISION

There are three kinds of cone in a human retina, all three respond to more than one colour, but each  particular cone is sensitive either to blue, green or yellow. Yellow light stimulates the green and yellow cone but red light affected the yellow sensitive of redness.

When all three types of cones are equally stimulated, we get the sensation white light.

3. A STIGMATION

This is a condition in which the cornea or lens is uneven such that is not focused properly on the retina. The defect can be corrected by using spectacles with special cylindrical lenses.

4. PRESBIOPIA

This condition, the lens cannot change its shape. It is brought about by loss in elasticity of lens and ciliary muscle due to old age can be corrected by the use of convex lenses

5. CATARACT

The lens gradually becomes cloudy so that light cannot pass through easily and the person cannot see properly. It may become gradually worse. The lens may have to be removed by operation and can be replaced by a plastic lens inside the eye.

6. GLAUCOMA

This defect is common in old people, glaucoma is caused by pressure in the eye.

7. COLOUR BLINDNESS

This is the genetic disorder in which a certain colour cannot be distinguished by man. A common type is red green blindness, individual is not in position to determine/distinguish between red and green colour.

8. TRACHOMA

These are a viral disease which affects the lighting of the eyelids. If not treated, trachoma can cause blindness.

DISEASES OF THE NERVOUS SYSTEM.

Most mental diseases arise as a result of malfunctioning of brain cells; May be due to:-

i. Accidents that damage the brain.

ii.  Brain infection.

iii.   A child born with brain defects.

iv. Drug abuse.

Diseases of the nervous system.

1.Meningitis: Is an infection of the Meninges (The membrane that cover the brain and spinal cord). Is caused by bacteria or virus.

2.      Psychosis: Is a disorder that result from self-edification or fear. Person imagines that there are unknown people who want to kill him or her.

-Psychotic must be referred to psychiatrist for treatment.

3.      Epilepsy: Is due to scar or damage of brain. It leads to periodical loss of consciousness accompanied by fits or convulsions, ie. Violent contractions of the skeletal muscles.  The disease is inheritable. Many cases of epilepsy can be controlled by medication, allowing the victims to lead normal lives.

4.      Leprosy: Is a bacterial disease which affects nerves in the limbs, it may also affect the iris. It causes painful white patches to appear on the skin and destroys the nerves.

5.      Tetanus: Is a bacterial disease which damage the nerves. The Tetanus bacillus found in the soil, penetrates through wounds. It causes muscular spasm followed by a generalized convulsion.

-Prevention: by immunization and rest.

6. Poliomyelitis: Is a viral disease, the patient becomes paralyzed in the affected region. Immunisation is necessary.

7.      Stroke: Is a sudden serious illness in the brain that can cause loss of the power to move or to speak clearly. This may be due to damage or blockage or bursting of the brain artery.

8.      Schizophrenia. Is a mental illness in which person is unable to link his or her thoughts to the real life. One suffers from delusion and life or imagination.

9.      Nervous breakdown. A mental problem affecting the brain due to worry or over working. The victim is over whelmed by feeling of despair or depression.

10.  Neurosis: Is a mental problem that cause an abnormal behavior, ie. Strong worry or fear (phobias) which he or she wants to over come. Eg. Obsession of being clean, where one washes hands continuously in fear of contamination.

11.  Cerebral malaria. Is a protozoan disease caused by various types of plasmodium, eg. Plasmodium  malariae/vivax/falciparum/ovale. When these parasites reach central nervous system will cause severe inflammation of meninges covering the brain.

-Signs: high fever, severe headache, vomiting, restless and begins to behave abnormally.

12.  Parkinson’s disease. Is a disorder mostly found in elderly people. It affects the cerebral cortex that controls the activity of skeletal muscles. This result in rigid joints and uncontrollable trembling. It can be controlled by medication.

13.  Alzheimer’s disease. Is a progressive and incurable disease which occurs in some people past the age of 50. It is characterized by forgetfulness and confusion. During the forgetfulness phase, there are annoying problems of learning and memory. The victim easily forgets.

DRUGS AND DRUG ABUSE

   Drugs 

This is any substance natural or synthetic, which has a physiological action on a living body.

It can be used for the treatment of disease on the alleviation of pain. 

are chemical substances used as medicine, narcotic, or stimulant which bring about changes in the functions of the body. Drugs have both psychological and physiological effects in human body.

    Normally drugs are taken to alleviate pains and fight diseases. However drugs are sometimes abused, eg. drugs used for wrong therapy, taken without a need, or wrong dose or use of drugs for non-medical reasons.

Psychoactive Drugs.
  Are drugs that affect central nervous system. 

-They produce false sense of well being and relief of someone from tension, anxiety, stress and pain
.

Types Of Psychoactive Drugs.
1.      Stimulants: stimulate or excite the nervous system. They speed up brain activities and body processes. They facilitate attention (being awake eg miraa), increase motivation, performance and efficiency. Example cocaine, heroin, and nicotine.

-common and less dangerous are caffeine from coffee, tea and cola.

-others are marijuana (bhang), miraa (Khat), cannabis.

2.      Sedatives:  Are sleeping inducing , slow down brain, anaesthetic effect, inducing the feeling of cheerfulness, happiness and pleasure (releasing depression).

-Examples; Valium, mandrax, alcohol.

       Depressants-sedatives.

        Tranquillisers – calming.

        Berbituarates- relaxants.

3.      Pain killers; suppress pain centres in the central nervous system (brain and spinal cord). They may cause brain damage.

4.      Inhalants; are volatile solvents which are used as intoxicating drugs. Eg. compounds of glue, kerosene, toluence and petroleum.

5.      Hallucinogens: they distort the way the brain interprets impulse, disturbance in coordination and movement.

-Illusion: brain altering message about something real.

-Hallucinations: brain may produce image with no basis in reality. Sometimes the users see vivid images and have feeling of well being. They (users) may show signs of mental illness, ie. confusion, violence, fear, and depression.

-Examples are lysergic acid diethylamide, mescaline and phencyclidine.

-          Others are cannabis (marijuana, hashish, bhang, charas and ghanja).

6.      Narcotics: They depress cortex in the brain, hence they dull the senses and relieve pain(they cause one to sleep or feel very relaxed). They bring deep sense of well being, reduction of fear and warm sensation of the stomach because they affect the thalamus ( the body’s mood- regulating centre.).
  Examples of opiates derived from opium.

-Codeine- to relieve pain and suppress cough.

-Morphine- to dull severe pain.

-Heroine –is stronger and more addictive than other opiates, is not used in medicine.

Forms Of Drug Taking.
1.      Intravenous. Is injecting a chemical into the vein.

2.      Inhalation : is inhaling volatile solvents like petrol, glue or paint.

3.      Oral; taking drug through mouth.

4.      Smoking; taking drug through smoking like marijuana (bhang or ganja).

5.      Sniffing; taking drug by sniffing through the nose, eg. cocaine.

 DRUG ABUSE (Drug Misuse And Addiction.)

Drug abuse 

This is when drugs are used for non – medical reasons with no regain to their side effects. 

or

is the indiscriminate and excessive use of psychoactive drugs for non-medical reasons with no regard to their side effects.

or

is the state of dependence caused by regular use of psychoactive drugs.

Withdrawal; is the painful reaction when drug is discontinued. It may cause severe tremors, sweating, and anxiety. It may also progress to physical illness (ailments) like cramps, muscle pains, nausea vomiting, nausea and convulsion.

Tolerance; is the condition in which large doses of drugs are needed to produce the desired results.

 Drug addiction is to depend up on drug so that life becomes unbearable without it 

-up if there is a sudden cut –off the drug, a person suffers withdrawal system 

Types Of Drug Addiction.
1.      Psychological or mental addiction; person thinks that his/her well being depends on the drugs and is unable to stop taking it ie user has an emotional need.

2.      Physical addiction; the body needs the drug in order to work properly. If there is no drug the person suffer severe pain and withdrawal symptoms.

Addicted people; can not live properly without drug unless they get proper help from educated people in the clinics or institutions. They need proper counselling, mental and physical treatment.

The common drug abuse used are

1. CAFFEINE

This is bitter substance found in, tea, soft drink, chocolate, kola nuts and certain medicine. It has the same effects on the nervous system accelerate the heart rate and increase the amount of sugar in blood. These have negative effect on the well being of the human body.

      2. NICOTINE

Is found in tobacco it has the same effects on the nervous system as that of “Caffeine” smoking linked with cancer of lungs, mouth throat, larynx, gullet bladder and pancreas. Also thinning and weakening of long tissue, smoking delay the healing of stomach ulcers, reduce sense of smell and taste. 

     3. COCAINE

Is found in the leaves of nuts and of the coca plants, have the same effect as nicotine. 

     4. ETHLY ALCOHOL

Is found in alcohol and beer, it enforce with the transmission of nerve impulses at synapse little alcohol have a stimulation effects large among distorts vision and interfere with hearing

The person becomes insensitive to touch, experience difficult is speaking. Ethyl alcohols slow reflexes and interfere with concentration and distance judgment. This is why people are advised not to drink when driving.

 

1. OPIUM,MARPHINE,HEROIN AND METHADONE

These are found in capsules of the poppy plant. These drugs rise to feeling of person and power. They interfere with nerve impulse transmission resulting in a positive affecting the well being of the body. If inhaled in appreciable amounts with either chlorofluocarbon or benzene induces unconsciousness,similar to that produced by alcoholic intoxications.

 

2. VALIUM 

Interfere with impulses transmission other tasted to valium interfere with the function of the medulla

  

3. MARIJUANA & HARSHISH

They produced from a plant called Indian hemp. These drugs disturb the sense of judgment so that a person becomes careless and foolish. 

Measures To Control Drug Abuse.
1.      Avoid taking any drug without doctor’s prescription.

2.      Keep off from peer pressure and addicted people.

3.      Be principled and say no to anyone who offers the drug to you.

4.      Use your leisure time properly, eg. games, sports and hobbies.

5.      Inform community leader or police of any use or trafficking of drugs.

6.      Form counselling club to educate people on how to keep off from drugs (education on proper use of drugs)

7.      Addicts should seek help from health officials.

8.      If medicine (Sleeping pills) does not bring improvement, consult the doctor. Do not overdose.

Reasonable Use of Drugs.
1.      All medicines be taken according to doctor’s prescription.

2.      Complete the dose as prescribed by doctor.

3.      Medicine that cause allergic reactions should not be taken.

4.      Drugs are taken with lots of water but NOT alcohol. Water help to excrete harmful substances in the body.

5.      Pregnant and breast feeding mothers should avoid taking medicine unless absolutely necessary and prescribed by the doctor.

6.      Avoid unnecessary use of some antibiotics(over-dose or under-dose make the drug powerless and pathogens resistant to it).

7.      If medicine does not bring improvement consult the doctor.

8.      Keep all medicine out of reach of children.

Reasons For Taking Drugs;
1.      Medical reasons- cure of diseases.

2.      Desire to satisfy curiosity about the effects of drugs.

3.      Pressure from peer  group (sense of belongingness to certain group)

4.      Desire to have new experience.

5.      To escape from reality of life, ie. hunger, poverty, family quarrels.

6.      To draw attention and resist the feeling of neglect.

7.      To be accepted by the members of peer group.

8.      For recreational and excitements purpose.

9.      To do away from unpleasant feelings and memories.

10.  Used as stimulants.

Effects Of Drug Abuse  (Excessive Use).  
1 Health Hazards:

1. Cigarette smoking can lead to lung cancer and heart diseases.

2. Bhang affects reproductive system by attenuating rate of sperm production.

3. Alcohol cause brain damage.

3.      Some drugs (like miraa) causes ulcers and rotten teeth.

4.      Many drugs affect the brain and give false sense of happiness.

5.      Many drugs lead to addiction (physical and psychological) and withdrawal.

6.      Some drugs (sleeping tablets) may lead to kidney damage.

7.      When overused, most drugs lead to damage of body organs like brain, heart, lungs and kidney.

8.      Pregnant women can affect their unborn baby.

 2.  Socio-Economic Hazards of Drug Abuse:

1. Drug addicts fail to concentrate at work (poor outcome).

2. Drugs weaken our bodies- poor development of the society.

3. Addicts indulge in irresponsible behaviour which can lead to unwanted pregnancies, STD’s and HIV/AIDS.

4. Student addicts mostly drop out of school or absent themselves.

5. May lead to traffic offences and accidents eg alcohol..

6. Economic burden to others as the addicts do not work.

7. Drug addiction can lead to marriage breakdown.

8. Drug addiction lead to more crime.

2.HORMONAL CO-ORDINATION IN MAMMALS

Endocrine system

Is the System that regulates the internal environment of the animal. The system consists of ductless glands which produce hormones. Since they have no ducts or tubes, the hormones are secreted directly into the blood stream. The hormones are transported through the blood to the target organ or tissue or cell.

Endocrine glands control slow and long term activities such as growth and sexual development e.g. sex hormones preparing female for ovulation, pregnancy, birth and lactation. But some are for particular moment e.g. adrenaline.

Feed back and interaction

For effective control, two opposing systems are needed like brakes and accelerator in the car. E.g. Adrenaline promotes the release of sugar into the blood, while insulin removes sugar the blood and stores it.

Feed back is needed so that the glands can adjust their output accordingly.

Fig.Position of endocrine gland in human being

Similarity between Nervous system and Endocrine system

1.      They are both set into action by a stimulus to produce a response.

2.      They both involve chemical transmission.

3.      They both provide means of communication in the body of an organism.

4.      The target organs in hormonal co-ordination are like the effector organs in the nervous co-ordination.

Differences between nervous system and Endocrine system

Activity	Nervous	Endocrine-Hormones
Methods of transmission	Neurone or Nerve impulse	Blood stream
Speed	Rapid	Usually slow
Duration of response	Short lived	Long lasting
Message or stimuli	Impulse	Hormone
Origin of message	Receptor and brain	Endocrine gland
Effector	Muscle or gland	Target organ or muscle

The endocrine glands

Endocrine means internal secretion. 

The endocrine glands Are ductless glands which secretes hormones into the blood stream. 

Hormonal coordination involves organs which secrete chemicals substance. This system is known as endocrine system which is composed glands and secretes chemical substance known as hormones.

These glands have no ducts, their secretions enter directly into the blood stream or body fluid by diffusion. The hormones are then transported through these media to the target tissues  or organs, where they initiate response.

Therefore hormonal coordination refers to the regulation of body functions through release of hormones. 

Hormones are organic compounds which are proteinous in nature. Hormones have either a generalized co-ordinating effect on the body or have localized (specific) co-ordinating effect in a particular target organ.

Some glands like pancreas are compound glands ie. They perform both endocrine and exocrine functions.

The exocrine glands

Are glands which have ducts or tubes through which the secretion move to the part of the body where they produce response. Examples are salivary gland, sweat glands and pancreas.

 Endocrine glands and their functions.

1.      Pituitary Gland

It is also called the master gland because it controls activities of other endocrine glands. 

It is found at the base of the fore brain attached to the Hypothalamus. It secretes several hormones. Examples:-

-Anterior lobe secret Trophic hormone which stimulate other endocrine glands to secrete hormones e.g. adrenocorticotropic hormone, thyroid stimulating hormone and gonadotropic hormone like luteinizing hormones.

-posterior lobe secret antidiuretic hormone.

Pituitary gland secret at least nine hormones which include the following;

i. Growth hormones (somatotrophin)

This influence protein metabolism and growth of bones, normal secretion of the hormones produce normal growth.

•  Over secretion of the hormones resulting in abnormal large size of the body, the condition is called GIGANTISM 
•  Under secretion result in dwarfism which may be resulting of  or .

ii. Follicle stimulating hormone (FSH) 

a.stimulates development of Graffias follicle in ovary. 

b Testis are stimulating hormone cause sperm production in males. 

iii. Anti – diuretic hormones (ADH)

increase the absorption of water from kidneys. 

iv. Luteinizing hormone (L.H)

brings about ovulation 

v. Prolactin hormone 

stimulates milk production in lactating mammals 

vi. Oxytocin brings about contraction of the uterus at birth, cause expulsion of milk from mammary gland. Hypo secretion birth is delayed while hyper secretion results in premature birth.

vii.Thyroid stimulating hormone(TSH): is for thyroid gland stimulation
viii. Prolatin hormone . For stimulates milk production in lactating mammals

 

2. THYROID GLAND

It produces Thyroxine. Is a butterfly shaped gland in the neck in front of the wind pipe below the larynx.

*Functions.

-Produces thyroxine and amino acids containing iodine

-Regulates rate of metabolism and respiration

-Influence mental and physical development and growth.

Complications:

Deficiency

-Cretinism in infants i.e. dwarfness and mental retardation.

Can be cured by administration of thyroxine in the early stage.

-Myxoedema in adults ie. Reduced metabolic rate, overweight, sluggish activity, thick skin, coarse hair and premature ageing

-Colloid Goitre: enlargement of thyroid gland

Excess:

-In adults, thinness, restlessness, over activity/excited and mentally unstable.

-Hyperthyroidism ie. Exopthalmic Goitre: enlargement of thyroid gland

3. PARATHYROID

This is found within the thyroid gland.

 It produces parathormone in response to a lack of calcium in the blood resulting increased absorption.

4. ADRENAL GLAND

These are found above the kidney. Are situated just above the kidney.

*The outer layer (Adrenal cortex) produces two hormones

-Glucocorticoids e.g. cortisol which accelerate glucose formation from non-carbohydrate sources like protein.

-Mineralocorticoid e.g. Aldesterone which stimulate re-absorption of sodium ions in the kidney ie.  controls the salt balance.

The inner zone (medulla) produces Adrenaline when stimulated by nervous system e.g. impulses of danger or other situations which need vigorous actions. Therefore, Adrenaline prepares body for emergency by rising blood pressure, increase heart beat and breathing rates, increasing blood sugar levels, increasing blood supply to the muscles while decreasing supply to the gut (alimentary canal) and skin.

Under secretion: causes Addison disease ie. Anaemia and weakness

Over secretion: Adrenogenital syndrome ie. Bearded lady.

Causes Cushing

-They produce adrenaline hormone which prepares the body for action in an emergence by rising blood pressure increasing heart and breathing rates, increasing

blood sugar levels and increasing supply of blood to the muscles. These actions prepare the individual to run away or to fight the enemy.

Adrenaline is thus referred to as a hormone of flight, or fight.

5. PANCREASE (Islets of langerhans)

Pancreas is a compound gland: Exocrine part produces digestive enzymes while endocrine part produces tow hormones ie. Insulin and Glucagon.

-Insulin which convert glucose into glycogen for storage in the liver and muscles.

-Glucagon which convert glycogen into glucose to be used in the body.

Complications: too little insulin causes Diabetes Mellitus ie. Excess of glucose in the blood.

Functions of Insulin

-promotes the uptake of glucose from blood by muscle cells.

-accelerate conversion of glucose into glycogen in the liver

-increases protein synthesis in some cells.

Produce insulin which lowers the level of glucose in the blood stream by causing the liver to store more glycogen.

6.   Gonads - Sex hormones (Gonadohormornes)

Are produced by ovaries of female and testes of male mammals.

Female sex hormones:

i. Oestrogen  (from the ovary)

, Functions:-

-development of female secondary sexual characteristics.

-prepares uterus to receive a ripe, fertilised ovum.

-maintain the uterus in a state where by it can nourish and protect the developing embryo ie. Prevent the contraction of uterus until the baby is due to be born.

-in some mammals, it brings female to "HEAT"

iiProgesterone

-promotes proliferation of uterine wall (inhibits eggs)

-formation of mammary glands (development of breasts) 

-It is concerned with maintenance of pregnancy. 

-It encourages the development of the uterus lining after ovulation. 

-It inhibits ovulation and prevents the uterus from contracting during pregnancy

iii. Relaxin 

-is also produced by ovaries begins as the time of birth approaches. 

-This hormone causes the ligaments between the pelvic bones to loosen providing a more flexible passage for the baby during bi

Male sex hormone:

i.Androgen or Testosterone from testis;

-development of male secondary sexual characteristics.

-production of sperms.

Complications for both females and males:.

a.Delay or lack of development of secondary sexual characteristics

COORDINATION AND MOVEMENTS IN PLANTS.

Plants can not move from one place to another. However they move by forces of wind. Plants move certain parts in response to the stimuli. Such movement include bending, twisting, and elongation. The movement is continuous and slow, so it can not easily be recognised.

Plants respond to a variety of stimuli in their environment. Unlike animals, plants cannot move from one place to another. However, they can move by forces of wind or water. Movement in plants in response to a stimulus is continuous and very slow. Movement of plants can be grouped into two: 

•  Growth movements 
•  Turgor movement 

1. Growth Movement 
These are the movements that take place in the meristematic regions due to unequal permanent growth. Growth movements can be classified into two categories namely: 

•  Autonomic movements 
•  Paratonic movements.

(a) Autonomic Movements 
These are self-controlled movements for instance growth in the meristematic regions i.e. tips of stems and roots. 
(b) Paratonic Movements 
These are the plant movements induced by external stimuli. These stimuli include: 
i Light           
ii  Moisture 
iii Gravity         
iv Chemicals 
v Touch 
Paratonic movements include tropic and nastic movements 

Tropic Responses 
These are growth movements that are caused by a wide range of stimuli. In this case the plant grows either towards or away from the stimulus. If the response is towards the stimulus it is referred to as positive. 
If the response is away from the stimulus it is referred to as negative. Tropic movements are mediated through plant hormones. 

Tropisms are growth movements by plant organs in response to a unilateral stimulus, in which the direction of the movement is related to the direction of the stimulus. 
Plant Hormones 
The first plant hormones were discovered by a Dutch botanist Fritz Went in the year 1928. Fritz Went called these hormones auxin or more accurately, indoleacetic acid (IAA). This hormone has an extremely powerful effect on growth. Like the animal hormones, plant hormones act in very low concentrations. A solution of 0.001 milligram in a litre of water applied to the side of a shoot is enough to cause bending. 

A part from auxins, plant hormones also include gibberellins and cytokinins. 

Auxins are synthesized from amino acid tryptophan in meristematic tissues such as the shoot tips, buds, young leaves and germinating seeds. 
Auxins increase cellwall elasticity by losing the bond between the cellulose fibres. 
Auxins promote cell division, cell elongation and cell differentiation. 
Effects of Auxins Concentration on Growth 
Experiments have revealed that higher concentrations of auxins stimulate growth in shoots while lower concentrations stimulate growth in roots. Amount of auxins which stimulate shoot growth, normally inhibit root growth 


              
Experiments demonstrating that a hormone regulates growth in shoots and roots 
  
Tropisms 
A tropism is a movement by a plant organ in response to a unilateral stimulus, in which the direction of the movement is related to the direction of the stimulus. Tropisms are named according to the nature of the stimulus. 
Types of Tropisms 
(i) Geotropism 
Geotropism is also known as gravitropism. 
This is the growth movement of plant parts in response to the direction of the force of gravity. The roots grow towards the direction of the force of gravity which means are positively geotropic (gravitropic).

Fig geotropism

The shoot grows away from the force of gravity which means are negatively geotropic (gravitropic). 
If a seedling is placed horizontally, the plumule will eventually grow vertically upwards while the radicle will grow vertically downwards. The above observation can be explained as follows: 

•  When the seedling is placed in a horizontal position, more auxin settles on the lower side of the root and shoots due to the pull of gravity. 
•  Shoots respond to a higher concentration of auxin than roots. In this case the lower side of shoot grows faster than the upper side, resulting in a growth curvature that makes the shoot grow vertically. 
•  Root growth is inhibited by high concentrations of auxins. Thus, the lower side of the root grows at a slower rate than the upper side where there is less auxin concentration. Consequently, this results in a growth curvature that makes the root grow vertically downwards                                                                                                   

(ii) Phototropism 
This is the growth movement of plant organs in response to a unilateral source of light. 
In an experiment it was revealed that auxins are directly involved in phototropism. If a shoot is exposed to light from one direction only, the shoot bends towards the source of light. Light causes an unequal distribution of the hormone (auxin). Light causes auxins to migrate to the darker side. In this case the auxins are more concentrated on the darker side than on the side where the light is coming from. The cells on the dark side grow faster and elongate than the ones on the side where the light is coming from. As a result, the shoot bends towards light. Shoots are positively phototropism because they grow toward the light. Some roots grow away from light, which means they are negatively phototropic. However many roots are not sensitive to light.  
              
                             
  
(iii) Hydrotropism 
That is growth movement of plant organs in response to unilateral source of water or moisture. In hydrotropism the root grows toward the source of water means the root are positively hydrotropic. On the other hand the shoot either grow away from the source of water meaning are 
negatively hydrotropic or show no response meaning are neutral. 
               
                                         
  
(iv)Thigmotropism 
The term thigmo comes from a Greek word thigma meaning touch. Thigmotropism is also referred to as haptotropism. In plants such as possiflora and gloriosa with tendrils which curl around and cling to stems, auxins also play a major role. When climbing stems or tendrils come into contact with a hard object, the contact causes them to curve and coil round the hard object. 
This is caused by the migration of the auxins from the point of plant contact and the hard object. In this case the part in contact with the hard object has a lower auxin concentration than the outer part. Higher auxin concentration promotes faster growth in shoots. Therefore, greater auxin concentration in the outer part causes faster growth than the part in contact with the object, hence the shoot continues to round the object.                                                  
                                                            
(v) Chemotropism 
This is the growth movement of plant organs in response to a unilateral source of chemicals. For instance, pollen tubes grow through the style towards the ovary and finally towards the ovules. 
(vi) Thermotropism 
This is the growth movement of plant organs in response to a unilateral source of heat as shown by movement of sunflower orienting itself towards the sun. However, there is an overlap between thermotropism and phototropism and sometimes a combination of both tropisms. 
(vii) Rheotropism 
This is the growth movement of plant organs in response to a unilateral source of air currents. 

Importance of Tropisms 
1. Phototropism: exposes the leaves of the plant to trap maximum sunlight for photosynthesis.
2. Haptotropism: enables plants with weak stems to obtain mechanical support. 
3. Geotropism: enables the roots of the plant to grow deep in the ground to provide anchorage.
4. Chemotropism: enables the growth of the pollen tube in flowering plants to facilitate fertilization. 
5. Hydrotropism: enables roots of the plant to obtain water. 

Nastic Responses 
These are non-directional movements of plant organs in response to diffuse stimuli, such as folding of leaves in warm weather, opening and closing of flowers in response to intensity of light and the closing of leaves when touched. Such movements occur as a result of changes in turgor pressure in certain cells. 




Types of Nastic Responses 
(a)  Nyctinasty 
This is a plant movement in response to temperature changes. This is a thermostatic movement; therefore nyctinasty is referred to as thermonasty. 
(b)  Photonasty 
This is a plant movement in response to a change in light intensity. Some flowers in certain plants open in presence of light and close in its absence. 
(c) Seismonasty 
This is plant movement in response to shock or vibration. 
(d) Hydronasty 
This is plant movement in response to changes in atmospheric humidity 
(e) Haptonasty 
This is plant movement in response to contact. The sensitive plant Mimosa pudica response to touch by folding up its leaves. 
(f) Chemonasty 
This is a plant movement in response to chemical stimuli. 
  
       Tactic Movement 
This is the movement of whole organism in response to an external stimulus. If the movement toward stimulus the tactic is positive, when the movement is away from the stimulus, the tactic is negative. Tactic movement is known as taxis. 
Types of Tactic Movement  
1. Phototaxis – locomotary response to light
2. Chemotaxis – locomotary response to chemical
3. Aerotaxis – locomotion response to variation in oxygen concentration 
4. Rheotaxis – locomotary in response to direction of water current 
5. Magnetotaxis – locomotary in response to magnetic field.
6. Osmotaxis - locomotary response to variations in osmotic pressure. 
7. Thermotaxis - locomotary response to temperature changes. 

Other Effects of Auxins 
(a)  Apical Dominance 
This refers to the inhibition of lateral bud development by the terminal bud. If the terminal bud is removed, lateral buds develop into side branches. This is because when the apical bud is cut and removed, the apical dominance is reduced. However, if the apical bud is cut and then a substance containing auxin is applied to the cut end, lateral buds do not sprout or develop. This experiment clearly indicates that apical dominance is brought by auxins. The principle of apical dominancy is applied in pruning. Removal of the terminal bud encourages the sprouting of side branches causing the plant to grow sideways instead of upwards. 

(b) Development of Adventitious Roots 
Adventitious roots are the roots that develop from a stem cutting. Plant cuttings which do not develop roots readily may be dipped in rooting auxins e.g. Indole Butyric Acid (IBA) and Naphthalene Acetic Acid (NAA). 
(c) Storage 
NAA is used to increase the period of dormancy in tubers and bulbs so that they can be stored for a longer period of time. 
(d) Parthenocarpy 
This is the formation of fruits without fertilization. Parthenocarpy can be inducedby treating unpollinated flowers with auxin. This phenomenon is applied in the development of seedless fruit varieties. 
(e) Falling of Leaves and Fruits 
Falling of leaves and fruits is brought about by a reduction in the concentration of auxins. Premature falling of fruits occurs due to the failure of the plant to produce adequate amount of auxins. This situation can be reversed by application of auxins. 
(f) Weed Killer 
In higher concentrations, auxins interfere with normal plant growth and can cause death. In this case auxins are used as herbicides or selective weed killers. 
(b) Gibberellins 
These are a mixture of chemical compounds which have an effect on plant growth. A common example of gibberellins is Gibberillic acid. Gibberillic acid causes stem elongation in plants. It stimulates rapid growth in dwarf varieties of certain plants by increasing the length of the internodes. Also used in breaking seed dormancy and inducing parthenocarpy. 
(c) Ethylene 
Speeds up ripening of fruits such as citrus 
(c) Abscisic Acid (ABA) 
Regulates fruit drop at the end of the season. 
(d) Cytokinins 
These are active growth substances which promote growth in plants in the presence of auxins. Cytokinins promote cell division by inducing growth of roots, leaves, callus tissue and repair or wounds in plants. 

Phytochromes 
These are pale blue-green compounds consisting of a pigment, which absorbs light energy. Phytochrome exists in two interconvertible forms. One absorbs red light at a wavelength of 665mm while the other one absorbs far red light at a wavelength of 725mm. 
effects: 
1. Elongation of the stem is stimulated by far-red light but inhibited by the red light, 
2. Leaf expansion is stimulated by the red light but inhibited by far-red. 
3. Lateral roots growth is stimulated by far-red and inhibited by the red light.
 4. Seed germination is stimulated by the red light but inhibited by the far-red light. 
  
Photoperiodism 
This is a flowering response in plants relative to lengths of day and night. When a plant is exposed to light, phytochrome absorbs light energy and P725 accumulates. P725 initiates the formation of a flowering hormone known as florigen, which is transported to the stem apices 
Types of Photoperiodism: 
i Short day plants 
ii Long day plants 
iii Day neutral plats 

i.Short-day 
These are the plants that require short-length illumination but shorter night periods to flower. Examples include chrysanthemum and poinsettias. 
ii Long-day Plants 

These are the plants that require longer day-length illumination but shorter night periods in order to flower. Examples include wheat and lettuce. 
iii.Day - neutral plant 

These are the plants that flower irrespective of day - length or right periods. Examples of day neutral plants include cotton and tomatoes.