In Central nervous system the myelin sheath is formed by:

Ans. A. OligodendrogliocytesApart from neurons, CNS also contains glial cells known as neuroglia. Number of glial cells is five times that of neurons Schwann cells found in peripheral nervous system are also glial cells. In the CNS there are three types of glia:MICROGLIA Scavenger cells which enter the CNS from blood vessels OLIGODENDROCYTES Involved in myelin formationASTROCYTES Produce substances that are trophic to neurons but their exact role is not known