myelin sheath

the insulating layer around many axons that increases the speed of conduction of nerve impulses. It consists of myelin and is laid down by glia, which wrap themselves around adjacent axons. The myelin sheath is interrupted by small gaps, called nodes of Ranvier, which are spaced about every millimeter along the axon. Also called medullary sheath.

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Psychology term of the day

April 24th 2024

cardiogram

n. a graphic tracing of some aspect of heart activity, usually electrical activity (see electrocardiogram). The tracing is produced by the stylet of a recording instrument called a cardiograph, and the procedure itself is called cardiography.