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myelin sheath
noun
: the insulating covering that surrounds an axon with multiple spiral layers of myelin, that is discontinuous at the nodes of Ranvier, and that increases the speed at which a nerve impulse can travel along an axon
called also medullary sheath
Examples of myelin sheath in a Sentence
Recent Examples on the Web
Consistently training your brain will help boost your cognitive processes over time, because the myelin sheath—the layer of protein that coats your nerves—thickens.
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Ayana Underwood, SELF, 14 Feb. 2024
That's because, in the vast majority of spinal cord injuries, the cord is not completely severed — rather, the myelin sheath that protects the nerve cells is damaged or destroyed.
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Eliza Strickland, Discover Magazine, 12 Oct. 2010
Sensory receptors in the skin, which lack the speed-boosting insulating layer called a myelin sheath, are among the slowest, at 1 mph.
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Valerie Ross, Discover Magazine, 14 May 2011
In earlier work, Hauser and his colleagues found that the tissue damage in MS is primarily directed by B cells, which attack the myelin sheath protecting nerves.
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Lydia Denworth, Scientific American, 13 Jan. 2022
In this case, your immune system mistakenly attacks your myelin and damages the myelin sheath.
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Sara Gaynes Levy, SELF, 7 Mar. 2022
In the case of MS, the body attacks its myelin sheath, a protective covering for the nerves in the brain and spinal cord.
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Jocelyn Solis-Moreira, Health.com, 21 Jan. 2022
In the disease, inflammation damages the myelin sheath that insulates nerve cells, ultimately disrupting signals to and from the brain and causing a variety of symptoms, from numbness and pain to paralysis.
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Lydia Denworth, Scientific American, 13 Jan. 2022
The mutations may damage the nerves or damage the myelin sheath, the protective coating that surrounds the nerve.
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Korin Miller, Health.com, 28 Sep. 2021
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Word History
First Known Use
1891, in the meaning defined above
Dictionary Entries Near myelin sheath
Cite this Entry
“Myelin sheath.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/myelin%20sheath. Accessed 8 Feb. 2025.
Kids Definition
myelin sheath
noun
: a layer of myelin surrounding the axons of some neurons
Medical Definition
myelin sheath
noun
: the insulating covering that surrounds an axon with multiple spiral layers of myelin, that is discontinuous at the nodes of Ranvier, and that increases the speed at which a nerve impulse can travel along an axon
called also medullary sheath
More from Merriam-Webster on myelin sheath
Britannica.com: Encyclopedia article about myelin sheath
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