Merck Manual

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Insulating a Nerve Fiber
Insulating a Nerve Fiber (2)
Insulating a Nerve Fiber

Most nerve fibers inside and outside the brain are wrapped with many layers of tissue composed of a fat (lipoprotein) called myelin. These layers form the myelin sheath. Much like the insulation around an electrical wire, the myelin sheath enables electrical impulses to be conducted along the nerve fiber rapidly.

When the myelin sheath is damaged, nerves do not conduct electrical impulses normally.