In humans, that portion of the nervous system that lies within the brain and spinal cord; it receives impulses from nerve cells throughout the body, regulates bodily functions, and directs behavior.

The central nervous system contains billions of nerve cells, called neurons, and a greater number of support cells, or glia. Until recently, scientists thought that the only function of glial cells—whose name means "glue"—was to hold the neurons together, but current research suggests a more active role in facilitating communication. The neurons, which consist of three elements— dendrites, cell body, and axon—send electrical impulses from cell to cell along pathways which receive, process, store, and retrieve information. The dendrites are the

message-receiving portions of the