Spinal Cord

Together with the brain, the spinal cord constitutes an important part of the central nervous system. It conducts impulses between the brain and the rest of the body and is a center for reflex activity. The spinal cord is present in the vertebral column of all vertebrate animals, running from the brain stem to the tail.

The spinal cord consists of a tube about 1 cm thick with a small central canal. Cerebrospinal fluid flow through this canal and around the spinal cord. The cord is encased in three membranes called meninges; the pia mater, the arachnoid, and the dura mater. In cross section, the spinal cord has centrally positioned butterfly shaped gray matter, consisting of unmyelinated cell bodies of nerve cell (neurons), surrounded by the myellinated axonal fibers, or white matter.

A cell body contains the nucleus of the nerve cell, and it sends out a single axon and numerous fibrous extensions known as dendrites. In the spinal cord, dendrites receive stimuli from the axons of other neurons whose cell bodies are located either elsewhere in the central nervous system or in the peripheral nervous system.

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