Nervous system is an important regulator and controls as well regulates the activities of all the other systems of body. It coordinates the reception of external stimuli and responds to them by sensory nerves and motor nerves. This system is divided into three parts: (1) Central nervous system, (2) Peripheral nervous system, and (3) Autonomic nervous system.

Central nervous system essentially consists of brain and spinal cord firmly lodged in the brain case and vertebral column. The brain controls voluntary actions, intelligence, memory, association, imagination and will. Cerebellum regulates the muscular movement of the body coordinating them. Medulla-oblongata controls involuntary action of breathing and hearbeat.

The spiral cord is an elongated cylindrical contravention of medulla and regulates various reflex actions. Peripheral nervous system consists of nerves which arise from the brain and the spinal cord. Autonomic system controls the internal activities of visceral organs, i.e., the circulation, digestion over which we have no voluntary control.