Conduction in myelinated axons depends on a similar pattern of circular current flow. However, myelin is an effective insulator, and current flow through it is negligible. Instead, depolarization in myelinated axons jumps from one node of Ranvier to the next, with the current sink at the active node serving to electrotonically depolarize the node ahead of the action potential to the firing leve. This jumping of depolarization from node to node is called saltatory conduction. It is a rapid process that allows myelinated axons to conduct up to 50 times faster than the fastest unmyelinated fibers. Ref: Ganong's Review of Medical Physiology 23rd edition, Chapter 4.