Myelin

Myelin is a fatty substance surrounding the axons of both peripheral and central nervous system neurons as an insulating sheath. Its main function is to increase the conduction velocity of the nerves.

The way in which it accomplishes this function is by acting as a natural biological insulator for the very low potential electrical energy which makes up nerve impulses. In the absence of myelin sheathing, nerve conduction can be impaired or lost altogether by virtue of the fact that the energy of nerve impulses is lost into surrounding tissues rather than being contained within the neural pathways.