Why does myelin make white matter conduct signals so much faster? · Grey Matter

An action potential on a bare axon has to regenerate itself on every patch of membrane, which is slow (around 0.5 to 2 m/s).

Why does myelin make white matter conduct signals so much faster?

An action potential on a bare axon has to regenerate itself on every patch of membrane, which is slow (around 0.5 to 2 m/s). Myelin wraps the axon in many layers of insulating membrane, leaving short gaps, the nodes of Ranvier, where the sodium channels are concentrated; current flows passively under the insulation and the spike is regenerated only at the nodes, so it appears to jump from node to node. Large myelinated axons reach tens of metres per second, up to about 120 m/s, which is what lets distant brain regions exchange signals within milliseconds.