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Now look at Anatomy Exercise 2 to see the action of the three types of neuron. The red star indicates the direction of movement of a nerve impulse:

Anatomy Exercise 2

The term nerve fiber should not be confused with the term nerve. A nerve is a group of nerve fibers (axons or dendrites) enclosed in a connective tissue sheath; it may contain the fibers of both sensory and motor neurons.

Note a nerve impulse can pass from one neuron to another across a tiny gap called a synapse. Whether an impulse is transmitted or not depends on chemicals called neurotransmitters. These chemicals play a major role in the normal functioning of the nervous system.