Myelin sheaths are formed by glial cells called Schwann cells. The Schwann cells wrap around the axon of a nerve cell in a spiral pattern, forming multiple layers of insulation. This insulation significantly increases the speed of electrical impulses travelling along the axon. Myelin sheaths are also found in the central nervous system, where they are formed by oligodendrocytes.
glial cells ,
Schwann cells ,
oligodendrocytes