01:830:310 Lecture 3: Chapter 3
7 Jul 2016
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Document Summary
A myelin sheath is a lioprotein that wraps around the axon in layers and gives neurons their characteristic white matter appearance. The myelin sheath increases conduction ve- locity and is formed by glial cells: the oligodendrocytes in the cns and the schwann cells in the pns. The presence of the myelin sheath speeds up the impulse by 4 times. The types of glial cells are microglia and macroglia. Microglial cells are small cells that function as the clean up crew. Microglia arrive from macrophages and function primarily as immune cells. Macroglial cells originate in the brain and are divided into oligodendrocytes, schwann cells, and astrocytes. Oligodendro- cytes are in the cns and wrap myelin around cells. An oligodendrocyte simultaneously wraps myelin around several cells. They myelinate several segments of some axon or dif- ferent axons. Schwann cells are in the pns and wrap myelin around cells in the pns. Each schwann cell wraps myelin around one cell. (1 cell=1 wrap)
