The myelin sheath is formed around the nerve fibers in the central nervous system by:

(Oligodendrocytes): Ref: 63-G, 634-35-SL (80- Ganong 23rd)Functions of the neuroglial cells* Astrocytes - Astrocytes twist around the nerve cells and form the supporting network in brain and spinal cord.Astrocytes form the basis of blood brain barrier and thereby regulate the entry of substances from blood into brain tissues.* Microglia: - Phagocytic in functions* Oligodendrocytes: - responsible for the formation of myelin sheath also provide support by forming a semistiff connective tissue between the nerve cells.