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Human nervous system, illustration. The nervous system in humans consists of the brain (top) and spinal cord, which make up the central nervous system (CNS). The spinal cord runs down the backbone from the brain, seen here from behind. Branching out from the spinal cord to the rest of the body are the spinal nerves. These, and other nerves, form the peripheral nervous system (PNS). (KEYSTONE/SCIENCE PHOTO LIBRARY/MAURIZIO DE ANGELIS/SCIENCE PHOTO LIBRARY)