Node of Ranvier

Node of Ranvier
Diagram of longitudinal sections of medullated nerve fibers.
Medullated nerve fibers stained with silver nitrate.
Identifiers
MeSH	D011901
TH	H2.00.06.2.03015
Anatomical terminology

This article is about Anatomy, for the musical group see Nodes of Ranvier (band)

Nodes of Ranvier are regularly spaced gaps in the myelin sheath around an axon or nerve fiber. About one micrometer in length, these gaps expose the membrane of the axon to the surrounding liquid.

The myelin sheath is the fatty tissue layer coating the axon. The myelin sheath helps speed the neural impulse by making it possible for the impulse to jump from node to node as opposed to traveling down the axon in tiny increments.

An action potential is the sharp electrochemical response of a neuron that has been stimulated, or whose membrane potential has been changed by a nearby cell or an experimentor. In an action potential, the cell membrane potential changes drastically and quickly as ions flow in or out of the cell. The action potential "travels" from one place in the cell to another, but ion flow occurs only at the nodes of Ranvier. Therefore, the action potential signal "jumps" along the axon, from node to node, rather than propagating smoothly, as they do in axons that lack a myelin sheath. This is known as saltatory conduction. This is due to clustering of voltage-gated Na+ and K+ ion channels at the Nodes of Ranvier. Unmyelinated axons do not have Nodes of Ranvier, voltage gated ion channels in these axons are randomly distributed.

The myelin sheath as well as the nodes were discovered by French pathologist and anatomist Louis-Antoine Ranvier (1835-1922)