Page "Axon" Paragraph 4

Axons are in effect the primary transmission lines of the nervous system, and as bundles they help make up nerves.

The length of axons is highly dependent on its location within the body.

Some axons can extend up to one meter or more while others stretch to as little as one millimeter ( inhibitory interneurons ).

The longest axons in the human body, for example, are those of the sciatic nerve, which run from the base of the spine to the big toe of each foot.

These single-cell fibers of the sciatic nerve may extend a meter or even longer.

The diameter of axons is also variable.

Individual axons are microscopic in diameter ( typically about 1μm across ), but may be up to several feet in length.

The largest mammalian axons ( PNS ) can reach a diameter of up to 20 μm.

The giant squid has axons that are close to 1 mm in diameter.

Mammalian axonal arborization ( the branching structure at the end of a nerve fiber ) also differs from one nerve fiber to the next.

Axons in the CNS typically model complex trees with several branch points.

In comparison, the cerebellar granule cell axon is characterized by a single T-shaped branch node from which parallel fibers extend.

Elaborate arborization is important for it allows for the simultaneous transmission of messages to a large number of target neurons within a single region of the brain.