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myelin sheath

American

noun

Anatomy.

a wrapping of myelin around certain nerve axons, serving as an electrical insulator that speeds nerve impulses to muscles and other effectors.

Etymology

Origin of myelin sheath

First recorded in 1895–1900

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

MS is a disease of the brain and central nervous system, in which the immune system mistakenly attacks the fatty myelin sheath that normally protects the nerves, like insulation around electric wires.

From BBC • May 29, 2026

The myelin sheath is a protective coating that surrounds nerve fibers in the brain and spinal cord.

From Science Daily • Apr. 15, 2026

When the organoids were exposed to ESI1, the treatment extended the myelin sheath of myelinating cells, the study reports.

From Science Daily • May 2, 2024

The thicker this myelin sheath, the faster the transmission.

From Science Daily • Mar. 6, 2024

"There may be a way to intervene so that you can increase the myelin sheath," he said.

From Science Daily • Jan. 14, 2024

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023