Nervous System

The nervous system has two main divisions: the central nervous system (CNS) and the peripheral nervous system (PNS) (Figure31). The CNS is the body’s control center, consisting of the brain and spinal cord. The brain is responsible for consciousness; its functions include perception, emotion, memory, thought, and language. The lower parts of the brain are also responsible for some unconscious functions, such as regulation of the endocrine (hormonal) and cardiovascular systems. The spinal cord is responsible for simple reflexes; it also serves as a pathway between the brain and the PNS.

The PNS is the body’s communication network; it includes the nerves and sense organs. Nerves are bundles of fibers that carry signals to and from the CNS. Motor nerves carry commands from the CNS to muscles and glands; sensory nerves carry input from sense organs (receptors) to the CNS. Different kinds of sensory receptors respond to differen..t