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An axon is a neuron process specialized for conveying signals to output contacts. In many neurons, an action potential begins near the axon initial segment and propagates along the axon to axon terminals, where neurotransmitter release can influence other biological cells.

One axon can branch and contact many targets. Its size, membrane ion channels and myelination affect transmission, while the pseudounipolar neuron illustrates that the soma need not lie directly in the main conducting route.^[ref]

Myelination forms layers of myelin around segments of an axon. Oligodendrocytes produce these sheaths in the central nervous system, while Schwann cells do so in the peripheral nervous system. Gaps, each called a node of Ranvier, allow action potentials to be regenerated between insulated segments, supporting saltatory conduction.

The arrangement affects when signals reach their targets, not just whether an axon is present. In mice, altered visual experience shortened segments wrapped in myelin along the optic nerve pathway and was associated with slower conduction along the optic nerve. The observations connected environmental input, myelin sheath geometry and a measured physiological consequence.^[ref] This experimental result does not imply that more myelin always produces a uniformly faster or better-performing nervous system; segment geometry and the timing required by a circuit matter.

White matter is neural tissue rich in long bundles of axons and their supporting cells. Extensive myelination contributes to its pale appearance and affects signal conduction. Damage can disrupt communication among regions without directly destroying the cortical cell bodies that originate or receive those pathways.