Nerves and Nerve Tracts

NERVES AND NERVE TRACTS

A nerve is a group of axons and/or dendrites of many neurons, with blood vessels and connective tissue. Sensory nerves are made only of sensory neurons. The optic nerves for vision and olfactory nerves for smell are examples of nerves with a purely sensory function. Motor nerves are made only of motor neu-rons; autonomic nerves are motor nerves. A mixed nerve contains both sensory and motor neurons. Most of our peripheral nerves, such as the sciatic nerves in the legs, are mixed nerves.

The term nerve tract refers to groups of neurons within the central nervous system. All the neurons in a nerve tract are concerned with either sensory or motor activity. These tracts are often referred to as white matter; the myelin sheaths of the neurons give them a white color.