The human nervous system is like a network of wires that lead from the brain, establishing contact with every portion of the body The brain is the center of this system. From the brain, orders go forth over the nerve wires and make us move, laugh, eat, and otherwise behave like human beings.

The nerves also serve the brain as messengers. Through a special part of the nervous system, the brain is informed of everything that happens to the body. The main line of communication connecting brain and body is the spinal cord. It is enclosed within the backbone. The spinal cord is really a grouping together of the nerve trunks, similar to the grouping together of wires to form a cable.

Each trunk is composed of two sections called the dorsal (back) and ventral (front) roots. The dorsal roots are the ones that carry messages to the spinal cord, and from there to the brain. The ventral roots transmit the messages from the brain to the various parts of the body. The dorsal roots control sensation; the ventral roots control action. When someone touches use we feel it through the dorsal nerve roots. If we move, the stimulus passes from the brain through the ventral roots.

This nervous system is called the cerebrospinal nervous system. takes care of all our voluntary actions and our responses to external stimuli. Without this nervous system, there would be no thought, action, or sensation.

But as you know, the body also carries on involuntary actions. Vital organs have certain duties to perform which are done without conscious thought on,our part. For example, digestion and breathing are carried on automatically and independently. Heart action is also automatic.

These involuntary actions, and many others, are carried on automatically by another nervous system called the automatic system. It does not require conscious control, though it does respond to stimuli from the cerebrospinal system. It forms a separate network within the body without which life would cease. So we need both systems to live and to function as human beings.