mýelínið

Myelín is a fatty insulating sheath that surrounds the axons of many neurons in the vertebrate nervous system. It is primarily composed of lipids and proteins. This myelin sheath is not continuous but is interrupted at regular intervals by gaps called nodes of Ranvier. The formation of myelin is a process called myelination, and it is carried out by specialized glial cells. In the peripheral nervous system, Schwann cells form myelin, while in the central nervous system, oligodendrocytes perform this function.

The presence of myelin significantly increases the speed at which nerve impulses, or action potentials, can travel along an axon. This is achieved through a process known as saltatory conduction, where the electrical signal jumps from one node of Ranvier to the next, bypassing the myelinated segments. This rapid transmission of signals is crucial for many bodily functions, including motor control, sensory perception, and cognitive processes. Damage to the myelin sheath, as seen in diseases like multiple sclerosis, can severely impair nerve function, leading to a range of neurological symptoms.