Myelinated Axons SEM

The main purpose of a myelin layer (or sheath) is to increase the speed at which impulsespropagate along the myelinated fiber. Along unmyelinated fibers, impulses move continuously as waves, but in myelinated fibers, they hop or “propagate by saltation.” Myelin decreases capacitance across the cell membrane, and increases electrical resistance. Thus, myelination helps prevent the electrical current from leaving the axon. (from wikipedia)
Image from 2012 National Center for Microscopy and Imaging Research. Image by Thomas Deerinck.

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