Nerve cells are more sensitive to oxygen deficiency than are any other cells of the body and are among the first to die if the blood supply is interrupted. If you could look beneath your skin, the nerves would appear as small, whitish threads running across the surface of your muscles. Each nerve contains hundreds, if not thousands, of axons, each sprouting from its own soma. The somas may be far away inside the brain or spinal cord or they may be in one of the clusters of somas called ganglia which are scattered throughout the body. There are two kinds of nerves, spinal and cranial.
Cranial nerves emerge from the brain and the spinal nerves emerge from the spinal cord.
Cranial nerves V, VII, IX, X, and XI are mixed nerves that contain sensory and motor fibers. Spinal nerves are all mixed. Another way of dividing up fibers depends on the type of organs they serve. Autonomic fibers connect the CNS to the visceral organs and somatic fibers serve the rest of the body. Thus, autonomic sensory fibers carry information about the state of the visceral organs and somatic sensory fibers conduct information from the receptors in the skin, joints and tendons.