Axon

What is an axon?

An axon is a long projection from a neuron that carries signals toward other cells. These electrical impulses are called action potentials. The Neuroscience overview of electrical signaling describes how action potentials propagate along axons, allowing communication over distances within the nervous system.

Myelinated and unmyelinated axons

Some axons are surrounded by myelin, while others are unmyelinated. As described in the discussion of neuroglial cells, oligodendrocytes produce myelin in the central nervous system and Schwann cells do so in the peripheral nervous system. Myelin speeds conduction. Gaps in the sheath, called nodes of Ranvier, allow the signal to be regenerated at intervals along a myelinated axon. This is called saltatory conduction.

Axon branches and connections

Axons can branch. An axon collateral is a branch that allows one neuron to connect with additional targets. Rockland’s review of axon collaterals describes how branches from a single neuron can reach different brain structures.

An axon can carry a signal to another neuron or to a muscle fiber. A motor neuron, for example, sends its signal along an axon to a muscle at the neuromuscular junction. At chemical synapses, specialized terminal regions release neurotransmitter; see axon terminal.