The nervous system is a complex, sophisticated system that regulates and coordinates the body's basic functions and activities. It is made up of two major divisions, including the central nervous system (consisting of the brain and spinal cord) and the peripheral nervous system (consisting of all other neural elements). The central nervous system controls thought, behavior, and movement. The peripheral nervous system relays information to the central nervous system for transmitting messages to muscles and glands.

In addition to the brain and spinal cord, principal organs of the nervous system include the following:

The nervous system is vulnerable to various disorders. Because of its complexity and the high technology used in evaluation and treatment of its disorders, the branches of medicine, physician specialists, and clinical services that manage it are as numerous and varied as the disorders and conditions.