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.