Nervous System

Nervous System

Under this system thin thread like nerves are spread throughout the body. After receiving the information of environmental changes from the sensitive organs, it spreads them speedly like electrical impulses and establishes working and coordination among different organs.

Nervous System of human is divided into three parts :
1. Central Nervous System
2. Peripheral Nervous System
3. Autonomic Nervous System

1. Central Nervous System

Part of the nervous system which keeps control on the whole body and on nervous system itself is called Central Nervous System. The Central Nervous System of human is made up of two parts - Brain and Spinal Cord.


Brain is covered by membrane called meninges. It is situated in a bony box called craninum which protect it from external injury.

(A) Fore Brain
» The function of the Cerebrum: This is the most developed part of the brain. This is the centre of wisdom, memory, will power, movements, knowledge and thinking. The analysis and coordination of muscular movement received from sense organs.
» The function of thalamus : It is the centre of the pain, cold and heat.
» The function of hypothalamus : It controls the hormonal secretion of endocrine glands. Hormones secreted from posterior pituitary gland secrete through it. This is the centre of hunger, thirst, temperature control, love, hate etc. Blood pressure, metabolism of water, sweat, anger, joy etc are controlled by it.

(B) Mid brain
The function of Corpora quadrigemina : This is the centre of control on vision and hearing power.

(C) Hind Brain
» Function of cerebellum : It is some what at the back of head and consist of two cerebellar hemisphere like cerebrum. It is large reflex centre for coordination of muscular body movements and maintenance of posture.
» Pons : It act as bridge carrying ascending and descending tracts between brain and spinal cord.
» Medulla : It is posterior most part of brain and continuous into the spinal cord It connect and communicate the brain with spinal cord. It contains the cardiac respiratory and vasomotor centres that control complex activity like heart action, respiration, coughing, sneezing etc.

» The brain of the human is covered in the cranium which protects it from external injury. Brain is covered by membrane called meanings.

Spinal cord

The posterior region of the medulla oblongata forms the spin cord.

Spinal cord main functions are :
» Coordination and control of reflex actions i.e. it works as the centre of the reflex actions.
» It carries the impulses coming out of brain.

2. Peripheral Nervous System

Peripheral Nervous System is made up of the nerves arising from brain and spinal cord. These are called cramal and spina nerves respectively. There are sensory, motor and mixed nerve.
» There are 12 pairs of cranial nerves and 31 pairs of spinal nerve found in a human.
» The unit of nervous tissues is called Neuron or nerve cell.

3. Autonomic Nervous System

Autonomic Nervous System is made up or some brain nerves and some spinal cord nerves. It supplies nerves to all the and blood vessel of the body. Langley, first presented the concept of Autonomic Nervous System in the year 1912.

There are two types of Autonomic Nervous System
(a) Sympathetic Nervous System
(b) Parasympathetic Nervous System

Functions of Sympathetic Nervous System
1. It narrows the blood vessels in the skin.
2. By its action hair gets erected.
3. It reduces the secretion of salivary glands.
4. It increases the heart beat.
5. It increase the secretion of sweat glands.
6. It stretches the pupil of eye ball.
7. It relax the muscles of urinary bladder.
8. It reduces the speed of contraction & relaxation of intestine.
9. The rate of respiration increase.
10. It increases the blood pressure.
11. It increases the sugar level in the blood.
12. It increases the number of Red Blood Corpuscles in the blood.
13. It helps in clotting of blood.
14. Collective impact of this affects fear, pain and anger.

Functions of Parasympathetic Nervous System :
The functions of this system is normally the opposite of Sympathetic Nervous System.
1. It widens the lumen of blood vessels except the coronary blood vessels.
2. It increases the secretion of saliva and other digestive juices.
3. The contraction of pupil is caused by this.
4. It creates contraction in the other muscles of the urinary bladder.
5. It creates contraction and motion in intestinal walls.
6. The effect of this nervous system collectively creates the occasion of rest and joy.