Dictionary.com
Thesaurus.com

myelin sheath

American  

noun

Anatomy.

  1. 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.

The research showed that MS first targets the myelin sheath.

From Science Daily • Oct. 21, 2025

In MS, the immune system mistakenly attacks the myelin sheath, a protective layer that insulates nerve fibers.

From Science Daily • Oct. 11, 2025

Her treatment involves an infusion every six weeks to help reduce the amount of damage and scarring to the myelin sheath.

From BBC • Apr. 25, 2023

Some axons are covered with a special structure called a myelin sheath, which acts as an insulator to keep the electrical signal from dissipating as it travels down the axon.

From Textbooks • Apr. 25, 2013

The myelin sheath is produced by glial cells.

From Textbooks • Apr. 25, 2013

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

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.