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Douglas Harper's Etymology Dictionary

"axis of the vertebrate body," 1842, from Greek axon "axis" (see axis).


n. (context cytology English) A nerve fibre which is a long slender projection of a nerve cell, and which conducts nerve impulses away from the body of the cell to a synapse.


n. long nerve fiber that conducts away from the cell body of the neuron [syn: axone]


An axon (from Greek ἄξων áxōn, axis), is a long, slender projection of a nerve cell, or neuron, that typically conducts electrical impulses away from the neuron's cell body. Myelinated axons are known as nerve fibers. The function of the axon is to transmit information to different neurons, muscles and glands. In certain sensory neurons ( pseudounipolar neurons), such as those for touch and warmth, the electrical impulse travels along an axon from the periphery to the cell body, and from the cell body to the spinal cord along another branch of the same axon. Axon dysfunction causes many inherited and acquired neurological disorders which can affect both the peripheral and central neurons.

An axon is one of two types of protoplasmic protrusions that extrude from the cell body of a neuron, the other type being dendrites. Axons are distinguished from dendrites by several features, including shape (dendrites often taper while axons usually maintain a constant radius), length (dendrites are restricted to a small region around the cell body while axons can be much longer), and function (dendrites usually receive signals while axons usually transmit them). All of these rules have exceptions, however.

Some types of neurons have no axon and transmit signals from their dendrites. No neuron ever has more than one axon; however in invertebrates such as insects or leeches the axon sometimes consists of several regions that function more or less independently of each other. Most axons branch, in some cases very profusely.

Axons make contact with other cells—usually other neurons but sometimes muscle or gland cells—at junctions called synapses. At a synapse, the membrane of the axon closely adjoins the membrane of the target cell, and special molecular structures serve to transmit electrical or electrochemical signals across the gap. Some synaptic junctions appear partway along an axon as it extends—these are called en passant ("in passing") synapses. Other synapses appear as terminals at the ends of axonal branches. A single axon, with all its branches taken together, can innervate multiple parts of the brain and generate thousands of synaptic terminals.

Axon (disambiguation)

An axon is part of a neuron.

Axon may also refer to:


  • Axon Automotive, British car manufacturer
  • Axon Group, British management consultants
  • Axon Labs, American health & wellness consumer product manufacturer


  • Axon (surname)
  • Axon Idea Processor, software package
  • Axon Framework, a development framework for Java
  • The Axons, an alien race from the Doctor Who adventure The Claws of Axos
  • Peter Axon, a character in the series Psi Factor: Chronicles of the Paranormal
Axon (surname)

Axon is an English surname. Notable people with this surname include the following:

  • David Axon (1951–2012), British astrophysicist
  • John Axon (1900–1957), English engine driver awarded the George Cross
  • John Axon (actor) (1960–2008), English actor; grandson of John Axon the engine driver

Usage examples of "axon".

It is the axon that is the nerve fiber in the typical nerve, and such a fiber, although microscopically thin, is sometimes several feet long, which is unusual, considering that it is part of a single cell.

However, in the living system it happens that the nerve impulse in the dendrites virtually always travels toward the cell body, whereas in the axon it travels away from the cell body.

For one thing, the rate at which a nerve impulse travels along an axon varies roughly with the width of the axon.

And yet why should invertebrates outpace vertebrates in axon thickness when the vertebrates have the more highly developed nervous system?

The axon is like a thin line running down the axis of the interrupted cylinder formed by the myelin sheath.

The axon stretches so far from the cell body that it seems quite reasonable to assume it can no longer maintain active communication throughout its length with the cell nucleus and the nucleus is vital to cellular activity and integrity.

The acetylcholine liberated at the axon endings of one nerve will affect the dendrites, or even the cell body itself, across the synapse and initiate a new nerve impulse there.

The axon of a neuron may make a junction not only with another neuron but also with some organ to which it carries its impulse, usually a muscle.

Again there is no direct fusion between the axon and the muscle fibers.

An axon which has degenerated through injury or disease can sometimes be regenerated, provided its neurilemma has remained intact.

The axon of this second cell leads outward by way of an appropriate peripheral nerve to the muscle, gland, or other organ that is to give the response.

The diagram shows only the conducting portion of the axon, or axis cylinder.

The axis cylinder, however, is the only part of the axon concerned in the transmission.

A neuron consists of a soma, which is its central cell body, and an axon and dendrites.

The axon and dendrites are thin branching tubes that form tree-like structures coming out of the soma.