THE NERVOUS SYSTEM IS THE BODY’S internal, electrochemical, communications network. Its main parts are the brain, spinal cord, and nerves. The brain and spinal cord form the central nervous system (CNS), the body’s chief controlling and coordinating centers. Billions of long neurons, many grouped as nerves, make up the peripheral nervous system, transmitting nerve impulses between the CNS and other regions of the body. Each neuron has three parts: a cell body, branching dendrites that
receive chemical signals from other neurons, and a tubelike axon that conveys these signals as electrical impulses.
