MedlinePlus Medical Encyclopedia: Myelin

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Myelin

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Illustrations	Definition

Illustrations

Myelin and nerve structure

Definition Return to top

Myelin is an insulating layer that forms around nerves, including those in the brain and spinal cord. It is made up of protein and fatty substances. The purpose of the myelin sheath is to allow rapid and efficient transmission of impulses along the nerve cells. If the myelin is damaged, the impulses are disrupted. This can cause diseases like multiple sclerosis.

Update Date: 5/22/2007

Updated by: Joseph V. Campellone, M.D., Division of Neurology, Cooper University Hospital, Camden, NJ. Review provided by VeriMed Healthcare Network.

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