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Nerve fibers are wrapped in a fatty sheath that lets a signal jump instead of crawling along.

Biology Facts, sourced to MedlinePlus.

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Myelin is an insulator with regular gaps in it, and the electrical signal leaps from gap to gap rather than propagating smoothly down the whole membrane. That raises conduction speed by more than an order of magnitude and costs far less energy. Diseases that strip the sheath, such as multiple sclerosis, leave the nerve intact and the signal unable to travel properly.

The claim comes from MedlinePlus, and the page it comes from was read on 2026-08-27 to confirm it still says this.

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