Small gaps of exposed cellular membrane that are not covered by the myelin sheath in a myelinated axon. Nodes of Ranvier contain clusters of voltage-gated Na+ ion channels that can regenerate the action potential as it propagates along the axon. 

Brandeis University

Saltatory conduction is the process by which an action potential propagates along a myelinated axon, appearing to 'jump' in a leapfrog fashion between the Nodes of Ranvier. At each node, an influx of sodium ions generates the action potential. These ions then diffuse to the adjacent section of the axon, raising its charge past the threshold of excitation and triggering a new influx of sodium ions at the next node. This mechanism allows the electrical signal to travel rapidly down the axon.

Saltatory Conduction

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

Nodes of Ranvier

A nerve impulse travels significantly faster along an axon wrapped in a myelin sheath compared to an unmyelinated axon of the same diameter. Which statement best analyzes the underlying mechanism for this increased speed?

Consider two neurons of equal length. Neuron X's axon is wrapped in a fatty sheath that is interrupted by small, regularly spaced gaps. Neuron Y's axon lacks this sheath entirely. If both neurons are stimulated at one end with sufficient intensity to generate an electrical signal, which statement best analyzes the resulting signal propagation?

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