FIGURE 2-1 Cross section of the spinal cord.

SOURCE: Reprinted with permission, from Taber and Thomas, 1997. Copyright 2003 by F. A. Davis Company.

SPINAL CORD, NERVES, MUSCLES, AND THE SENSORY SYSTEM

The spinal cord is the elongated portion of the central nervous system (CNS) that connects the brain to all muscles of the body and most sensory nerves to the brain.1 It is surrounded and protected by vertebrae, or the spinal column. The outer edge of the spinal cord is the white matter (Figure 2-1), which contains the branching portions of nerve cells known as axons. Wrapping around the axons is a fatty whitish substance called myelin, which speeds up the nerve impulses from the brain to the rest of the body. In addition to an axon, each nerve cell (or neuron) has a cell body, which is its control center housing the nerve cell genes and other parts needed to

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Except for the cranial nerves to the head and neck.



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