NERVOUS COORDINATION

Coordination is the process by which all actions of different parts of the body of organisms are harmonized to achieve definite objectives.

All metabolic processes in the body of an organism do not function individually but are all closely linked and dependent on each other for effective function.

The two communication systems that bring about coordination are:

1. Endocrine system (hormone)
2. Nervous system.

The nervous system of a mammal is made up of two parts.

1. The central nervous system (CNS)
2. The peripheral nervous system (PNS)

CENTRAL NERVOUS SYSTEM

The central nervous system (CNS) consists of the brain which is enclosed in the cranium or brain box and spinal cord which runs down the centre of vertebral column (backbone).

THE BRAIN

The brain is the most specialized organ of human body. it is composed of millions of nerve cells called neurons. It is protected by the skull, cranium or brain box. The brain is divided into three important portions.

1. Fore brain
2. mid brain

iii.        hind brain.

FORE BRAIN:   The fore brain is divided into three parts. The cerebrum, olfactory lobes, thalamus and hypothalamus.

The CEREBUM is the largest part of the brain and it is made up of right and left hemispheres which are separated by a deep furrow called median fissure. The two halves are connected by a band of fibre called CORPUS CALLOSUM. The outer surface of the cerebrum is called cerebral cortex and is deeply folded in irregular pattern or convolution which increases the surface area of the cerebrum. The cortex consists of grey matter outside as a result of the colour of unsheathed nerve cell, while the inner part of the cerebrum is called white matter because the nerves cells are sheathed. Each cerebral hemisphere is divided into four lobes namely the frontal, temporal, parietal and occipital lobes.

FUNCTIONS OF CEREBRUM.

1. It is the seat of consciousness, intelligence, memory, judgment, learning, interpretation of sensation and imagination.
2. It controls all voluntary actions e.g. movement of legs, arm speech etc.

iii.        It collects information from sense organs and store such information (e.g. learning and behavior)for later use

OLFACTORY LOBES– These are two small structures placed anteriorly on the cerebrum.

THALAMUS- These are two ovoid structures attached to the back of the fore brain. It contains masses of grey matter.

FUNCTIONS

1. It is the center for sensation of pains, touch and anger
2. It is the seat of consciousness or awareness

iii.        It receives impulses from mid brain, hind brain and spinal cord

HYPOTHALAMUS

It lies below the thalamus and is connected to the pituitary gland. It contains reflex centre linked to the autonomic system. it plays  important role in homeostasis

FUNCTIONS

1. It controls sleep and alertness
2. it controls appetite or feeling

iii.        it controls temperature

1. it controls osmoregulation.
2. it controls the secretion of hormones from the pituitary gland
3. it is the seat of aggression and anger

THE MID BRAIN

The mid brain is narrow and short with thick walls portion which connects the hind brain and fore brain together. It consists of optic lobes, pineal body and pituitary gland.

FUNCTION

1. The optic lobes are the seat of sight or vision.
2. It connects the fore brain and hind brain thereby assisting transmission of impulses.

HIND BRAIN

The hind brain consists of three parts namely cerebellum, medulla oblongata and Pons varolli.

CEREBULLUM

It is located below the back of the cerebrum, oval in shape and consists of two hemispheres. It is less convoluted than cerebrum. The surface is covered with grey matter while the inner side is composed of white matter. It is connected to the semi-circular canals of the ears.

FUNCTION

1. It controls posture and balance of the body.
2. it controls most of involuntary action.
3. it receives impulses from auditory organs and skin.

PONS VAROLLI

It connects the two halves of the cerebellum and cerebrum to the medulla oblongata. It is made up of thick bundles of nerve FIBRES.

MEDULLA OBLONGATA

The medulla oblongata connects the cerebellum to the spinal cord. In medulla oblongata the white matter surrounds the grey matter. It is in the medulla oblongata that right and left motor fibers from the brain cross over each other, so that the left hemisphere controls the right side and the right hemisphere controls the left side of the body.

Functions

1. it controls many actions or movement of the body especially those concerned with respiration, heart-beat and digestion.
2. it controls the constriction and dilation of the blood vessels thus regulating blood pressure.

Human brain

SPINAL CORD:

It is an extension of medulla oblongata and passes through the neural canal of the back bone which protects it. The spinal cord is protected by the three layers of meninges namely Dura matter (outer layer), arachnoids matter (middle layer) and pia matter (inner layer). The spaces between these layers are occupied by cerebrospinal fluids which act as protective cushions. The outer portion contains white matter consisting of bundle of axon and dendrite. The inner portion contains grey matter is made up of intermediate neurons and cell bodies of motor neurons.

Functions

1. it coordinates simple reflect actions like knee jerk and automatics reflexes such as sweating.
2. it acts as a pathway between the spinal cord and the brain.

PERIPHERAL NERVOUS SYSTEM

The peripheral nervous system (PNS) consists of all nerves outside the brain and spinal cord. These are made up of sensory nerves which arise from all parts of the body to the central nervous system and the motor nerves running from the central to all parts of the body. The peripheral nervous system receives signals changes from the environment registered by the receptors or sense organs and send them to the central nervous system which integrates the information .it receives and send appropriate messages to the effectors accordingly.

The PNS consists of twelve (12) pairs of cranial nerves and thirty one (31) pairs of spinal nerves. The cranial nerves arise from the brain while the spinal nerves arise from the spinal cord. The peripheral nervous system is subdivided into two systems. These are;

(i) Somatic nervous (ii) automatic nervous system.

SOMATIC NERVOUS SYSTEM

The somatic nervous system consists of nerves without synapses lead from the brain through the spinal cord to skeletal muscles. They deal mainly with external stimuli and their responses. The sensory nerves transmit impulses from the external stimuli to the central nervous system and relay responses through the motor neurons or the body causing the body movement. The motor neurons stimulate the effectors i.e. muscle and glands. The somatic nervous system controls activities that are mainly voluntary.

AUTONOMIC NERVOUS SYSTEM (ANS)

The autonomic nervous system is the part of the peripheral nervous system which controls the involuntar7y actions inside the body such as the rate of heart, sweating, and peristaltic contractions of the intestine. The neuronal of the autonomic nervous system are connected to involuntary muscles of the internal organs.

The autonomic nervous system comprises of sensory and motor neurons. It arises from the central nervous system and is connected to different internal organs.

The autonomic nervous system consists of two parts namely

1. Sympathetic nervous system
2. Parasympathetic nervous system.

These two systems help to regulate the vital internal organs such heart, eye, lungs, kidney etc. maintaining a system of check and balances

SYMPATHETIC NERVOUS SYSTEM consists of nervous which connect internal organs to the thoracic and lumber area of the spinal cord. The sympathetic nervous system stimulates many parts of the body for necessary action in time of danger.

PARA- SYMPATHETIC NERVOUS SYSTEM consists of nervous which connect internal organs to the tenth criminal nervous and the sacral region of the same organ as sympathetic nervous system but its action is opposite or antagonistic to sympathetic nervous system.