Also found in: Thesaurus, Medical, Legal, Encyclopedia, Wikipedia.
The insulating envelope of myelin that surrounds the core of a nerve fiber or axon and facilitates the transmission of nerve impulses. In the peripheral nervous system, the sheath is formed from the membranes of Schwann cells, and in the central nervous system it is formed from oligodendrocytes. Also called medullary sheath.
a discontinuous wrapping of myelin around certain nerve axons, serving to speed nerve impulses to muscles and other effectors.
Switch to new thesaurus
|Noun||1.||myelin sheath - a layer of myelin encasing (and insulating) the axons of medullated nerve fibers|
axolemma - outer membrane covering an axon
oligodendria, oligodendroglia - tissue consisting of glial cells with sheetlike processes that form the myelin sheath of nerve fibers