Dictionary.net

nerve fiber

• a threadlike extension of nerve cell Slender processes of neurons, especially the prolonged axons that conduct nerve impulses. One units trunk; it is axis process a neuron and medullated, i. e. white substance Schwann (myelin), medullated; either the medullated non-axis-cylinder or may not be surrounded by primitive sheath neurilemma, so that there are four forms of nerve-fibers.