1-3. ORGANIZATION OF THE NERVOUS SYSTEM

The nervous system has two main divisions: the central nervous system (CNS) and the peripheral nervous system (PNS). The central nervous system is composed of the brain and the spinal cord. This system controls behavior. All body sensations are sent by receptors to the central nervous system to be interpreted and acted upon. All nerve impulses that stimulate muscles to contract and glands to secrete substances get the message from the central nervous system. The peripheral nervous system is composed of nerves. This system is a pathway to and from internal organs. PNS serves as a pathway to the brain for the five senses and helps humans adjust to the world around them. Further subdivision of the peripheral nervous system will be discussed later in this lesson.