The nervous system is the master controller of the body. Each thought, each emotion, each action—all result from the activity of this system. Through its many parts, the nervous system monitors conditions both within and outside the body. It then processes that information and decides how the body should respond, if at all. Finally, if a response is needed, the system sends out electrical signals that spur the body into immediate action. Although one of the smallest of the body's systems in terms of weight, the nervous system is the most complex and versatile.

Design: Parts of the Nervous System

The nervous system is a collection of cells, tissues, and organs. It can be split into two separate divisions: the central nervous system and the peripheral nervous system.

The central nervous system (CNS) acts as the command center of the body. It interprets...