myelin sheath – insulation around axons

(Pronounced my-uh-lin sheeth)

To remember the meaning of myelin sheath, use the following mnemonic:

My violin is kept in a sheath (myelin sheath) for insulation from axes falling on (axon insulation) it.

The myelin sheath is a fatty, white substance that wraps around the axons of nerve cells like insulation around an electrical wire. The primary function of it is to increase the speed of nerve impulse transmission along the axon, where the impulse jumps between gaps in the myelin called nodes of ranvier. This allows them to travel much faster than they would along axons without myelin sheaths. 

The myelin sheath also provides protection and support to the nerve fibre, helping to maintain its structural integrity. Damage to the myelin sheath, as occurs in diseases like multiple sclerosis, can significantly slow down or disrupt nerve signal transmissions, leading to various neurological conditions.