MEDICAL PHYSIOLOGY

Detailed explanation-1: -The myelin sheath is a greatly extended and modified plasma membrane wrapped around the nerve axon in a spiral fashion [1]. The myelin membranes originate from and are a part of the Schwann cells in the peripheral nervous system (PNS) and the oligodendroglial cells in the central nervous system (CNS) (see Chap.

Detailed explanation-2: -Glial cells are the key element for supporting the messages neurons send and receive all over the body. Much like the insulation around the wires in electrical systems, glial cells form a membraneous sheath surrounding axons called myelin, thereby insulating the axon.

Detailed explanation-3: -In the PNS, axons carry signals to muscles and glands or from sensory organs such as the skin. Each myelin sheath is formed by the concentric wrapping of an oligodendrocyte (CNS) or Schwann cell (PNS) process (a limb-like extension from the cell body) around the axon.

Detailed explanation-4: -The myelin sheath itself is made up of spirally arranged lamellae in which the intraperiod and dense lines alternate. Inside the myelin sheath an inner cytoplasmic process surrounds the axon and where the external surfaces of its bounding membrane come together an internal mesaxon is formed.