Functions of a Nervous System

Functions of a Nervous System in humans include the control of voluntary and involuntary activities that take place in the body and are regulated by different parts of the nervous system.

The nervous system of humans has three main parts. These are - central nervous system, peripheral nervous system and autonomous nervous system.

The central nervous system consists of the brain and the spinal cord. The brain controls the physiolocical functions and behaviour by receiving information from the sense receptors of the body through the spinal cord.

The peripheral nervous system comprises the nerves that connects the central nervous system with the sense organs and body muscles. There are two types of nerves. These are -

(a) Cranial Nerves - These nerves arise from the brain.

(b) Spinal Nerves - These nerves arise from the spinal cord.

These nerves serve the function of controlling the voluntary activities to and from the central nervous system

The autonomous nervous system controls

the activities of viscera that involve the involuntary activities.Hence it is also known as the visceral nervous system.It mainly consists of sympathetic nervous system ,parasympathetic nervous system and enteric nervous system.Some if the textbooks don't mention the enteric nervous system.The sympathetic nervous system helps the body in an emergency by increasing the heart beat. The parasympathetic nervous system plays its role after the emergency. The parasympathetic nervous system is opposite to the sympathetic nervous system. The autonomous nervous system helps in controlling the activities of many organs. For example -

1.Eyes - The sympathetic nervous system dilates the pupil of the eye . It makes the lens thicker for far vision.The parasympathetic nervous system constricts the pupil. It makes the lens thicker for near vision.

2.Salivary Glands - Secretion is inhibited and blood vessels are constricted by the sympathetic nervous system. Secretion is stimulated and the blood vessels are dialated by the parasympathetic nervous system.

3.Lacrimal Gland - Secretion is stimulated by the sympathetic nervous system while secretion is inhibited by the parasympathetic nervous system.

4.Skin - Sympathetic nervous system stimulates the secretion of the sweat glands. It also contracts the hair muscles to make hair stand up. The parasympathetic nervous system inhibits the secretion of sweat glands. It also inhibits the contraction of the hair muscles.

5.Lungs - The sympathetic nervous system dialates the bronchial smooth muscles. It inhibits the secretion of bronchial glands. The parasympathetic nervous system constricts the bronchial smooth muscles. It stimulates the secretion of the bronchial glands.

6.Heart - The sympathetic nervous system dialates the coronary arteries and raises the blood pressure and heart beat. The parasympathetic nervous system constricts the coronary arteries and lowers the blood pressure and decreases the heart beat.

7.Gastro-intestinal tract - The sympathetic nervous system inhibits peristalsis and inhibits the secretion of digestive glands. The parasympathetic nervous system stimulates peristalsis and stimulates the secretion of digestive glands.

8.Blood Vessels - The sympathetic nervous system constricts the peripheral blood vessels. The parasympathetic nervous system dilates the peripheral blood vessels.

9.Period of blood clotting - The sympathetic nervous system decreases the period of blood clotting while the parasympathetic nervous system increases the period of blood clotting.

10.RBC Count - The sympathetic nervous system increases the RBC count. The parasympathetic nervous system decreases the RBC count.

11.Pelvic Organs - The sympathetic nervous system inhibits the contraction of organ walls. It also stimulates the contraction of sphincters and inhibits secretion. The parasympathetic nervous system stimulates the contraction of organs. It relaxes sphincters and stimulates secretion.

12.Liver - The sympathetic nervous system promotes glycogenolysis and inhibits bile secretion. The parasympathetic nervous system promotes glycogenesis and promotes bile secretion.

13.Gall Bladder - The sympathetic nervous system relaxes the gall bladder. The parasympathetic nervous system contracts the gall bladder.

14.Intestinal Glands - The sympathetic nervous system inhibits the secretion . The parasympathetic nervous system promotes secretion.

15.Gastric Glands - The sympathetic nervous system inhibits the secretion. The parasympathetic nervous system stimulates the secretion.

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