The myelin sheath is a protective covering that surrounds the axons of many neurons in the nervous system. Its primary role is to facilitate rapid signal transmission along the axons through a process called saltatory conduction, which allows electrical impulses to jump between Nodes of Ranvier. This increased efficiency helps ensure fast communication between neurons, essential for various bodily functions, including reflexes and coordinated movement. Additionally, the myelin sheath contributes to the overall health and maintenance of neurons.