Myelin Sheath

The Myelin Sheath surrounds the core of a nerve fiber axon and facilitates the transmission of nerve impulses.

In peripheral nervous system, the sheath is formed from the cell membrane of the Schwann
cell and, in the central nervous system, from oligodendrocytes.

Myelin is an outgrowth of a type of glial cell. The production of the myelin sheath

Even though there is little myelin in the brain at called myelination. In humans, this production process begins in the fourteenth week of fetal development. The main purpose of the myelin sheath is to increase the speed where impulses propagate along the myelinated fiber. Along unmyelinated fibers, impulses move continuously as waves. The impulses that are in the myelinated fibers, they hop or "propagate by saltation". When there's a peripheral fiber that is severed, the myelin sheath provides a track where regrowth can occur. On the downside, this myelin layer does not always guarantee a perfect regeneration.

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