sarcolemma cells form the myelin sheath around nerve fibers in the pns.
sarcolemma cells form the myelin sheath around nerve fibers in the pns.
what cells form the myelin sheath around nerve fibers in the pns?
sarcolemma
myelin is a lipid-rich (fatty) substance formed in the central nervous system (cns) by glial cells called oligodendrocytes, and in the peripheral nervous system (pns) by schwann cells. myelin insulates nerve cell axons to increase the speed at which information (encoded as an electrical signal) travels from one nerve cell body to another (as in the cns) or, for example, from a nerve cell body to a muscle (as in the pns). the myelinated axon can be likened to an electrical wire (the axon) with insulating material (myelin) around it. however, unlike the plastic covering on an electrical wire, myelin does not form a single long sheath over the entire length of the axon. rather, each myelin sheath insulates the axon over a single section and, in general, each axon comprises multiple long myelinated sections separated from each other by short gaps called nodes of ranvier. each myelin sheath is formed by the concentric wrapping of an oligodendrocyte or schwann cell process around the axon.
myelin
when a peripheral fiber is severed, the myelin sheath provides a track along which regrowth can occur. however, the myelin layer does not ensure a perfect regeneration of the nerve fiber. some regenerated nerve fibers do not find the correct muscle fibers, and some damaged motor neurons of the peripheral nervous system die without regrowth. damage to the myelin sheath and nerve fiber is often associated with increased functional insufficiency.









































unmyelinated fibers and myelinated axons of the mammalian central nervous system do not regenerate.
myelin