An axon or nerve fiber's a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma. Anatomy Axons are in effect the primary transmission lines of the nervous system, and as bundles they help make up nerves. Individual axons are microscopic in diameter (typically about 1μm across), but may be up to several feet in length. The longest axons in the human body, for example, are those of the sciatic nerve, which run from… (More on Axon)