|Term: Myelin Sheath|
|Definition (Myers): A layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next|
|Definition (alternative): An insulating layer that forms around nerves, including those in the brain and spinal cord. It is made up of protein and fatty substances. The purpose of the myelin sheath is to allow rapid and efficient transmission of impulses along the nerve cells. If the myelin is damaged, the impulses are disrupted. This can cause diseases like multiple sclerosis. *|
|Contextual explanation: Myelin is the protective sheath around axons in the nervous system, and is often referred to as 'white matter.' It acts as an insulator to the electrical signal that is conducted down the axon as a neuron fires, and can well be compared to the insulation around an electrical wire. The myelin sheath contains a variety of fatty substances (lipids), and contains at least ten distinct chemicals. This insulation acts to increase the rate of transmission of signals.|
From what is known, axons are not fully myelinated at birth, but myelin is formed from birth on into the second decade of life. The way myelination takes place is through glial cells wrapping around the axons in a spiral fashion.
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|Edited by: Patrick|