Saltatory conduction

Saltatory conduction is the propagation of an action potential along a myelinated axon, with regenerative depolarization concentrated at gaps called nodes of Ranvier.

Node of Ranvier: A gap between adjacent myelin segments where an axon membrane is exposed and ion channels are concentrated. Action potentials are regenerated at these exposed gaps during saltatory conduction.
Membrane potential: The voltage difference across a biological cell membrane, produced by ion distributions and selective permeability. The local voltage changes that travel between nodes depend on this membrane property.
Multiple sclerosis: An immune-mediated disease in which damage to central nervous system myelin causes neurological dysfunction. Demyelination can disrupt saltatory conduction and slow or block impulses.
Continuous conduction: Propagation of an action potential by sequential activation along an unmyelinated axon membrane. Unlike saltatory conduction, it regenerates the impulse along the membrane rather than mainly at nodes.
Myelin sheath: A multilayered insulating membrane wrapped around axons by glial cells. It limits current leakage from internodes, allowing depolarization to spread farther between nodes.
Resting membrane potential: The stable voltage difference across a cell membrane when the cell is not generating an action potential. The axon membrane must return toward its resting state before it can fire again.
Guillain–Barré syndrome: A group of acute immune-mediated disorders that commonly damage peripheral nerves and cause weakness. Its demyelinating forms impair conduction along myelinated peripheral axons.
Unmyelinated axon: An axon that lacks the insulating myelin sheath around its membrane. Its action potentials propagate continuously rather than jumping between myelin gaps.
Voltage-gated sodium channel: A membrane protein that opens in response to depolarization and permits sodium ions to enter cells. Dense sodium channels at nodes regenerate the action potential.
Depolarization: A change in membrane voltage toward a less negative or more positive value. Depolarizing current arriving at a node can trigger its sodium channels.

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