Translation and vector of the File:Propagation of action potential along myelinated nerve fiber.png Image description: Schematic representation of the action potential propagation through myelinated nerve fiber of peripheral nervous system. From axon hillock of neuron body (soma) action potential propagates from one unmyelinated fiber part to the next one. The unmyelinated parts of the nerve fiber are 
nodes of Ranvier. This way of action potential propagation is called saltatory conduction (red arrows in the diagram) Ion channels open, allow sodium ions to enter the cell leading to membrane depolarization and generation of action potential.  Myelination of nerve fibers in the peripheral nervous system is achieved by Schwann cells wrapping around an axon part (cross section). The nucleus and most of the Schwan cell cytoplasm are contained in the outer most layer called neurilemma.  Own work loosely based on Raphael Alya R., Talbot William S. (2011). "New Insights into Signaling During Myelination in Zebrafish". Current topics in developmental biology 97: 1–19. DOI:10.1016/B978-0-12-385975-4.00007-3. ISSN 00702153.Min Y., Kristiansen K., Boggs J. M. at al (2009). "Interaction forces and adhesion of supported myelin lipid bilayers modulated by myelin basic protein". Proceedings of the National Academy of Sciences 106 (9): 3154–3159. DOI:10.1073/pnas.0813110106. ISSN 0027-8424.
Own work
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