3+development (3) - Class 3 Development parts meninges...

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Class 3 –Development, parts, meninges Review list: 1. What is a myelin sheath? What difference does it make if an axon is myelinated or not? Many axons are surrounded with a myelin sheath that increases the speed of axonal transmission (Beatty, 1995). This is especially important in longer neurons. Myelin is lipoprotein that wraps around the axon like the layers of an onion, giving neurons their characteristic white matter appearance. The sheath begins at the first segment of the axon, where the nerve impulse or action potential begins. The myelin serves as an electric insulator that increases conduction velocity. The myelin sheath is formed by glial cells, termed oligodendrocytes, in the CNS and by Schwann cells in the peripheral nervous system (PNS). The development of the myelin sheath corresponds to behavior. A myelin sheath is a fatty layer formed by Oligodendrocytes (CNS) or Schwann Cells (PNS) around Axons. Their presence increases the speed of information transmission by 4 times (120 m/s). 2. What are the types of glial cells? What is the function of microglia, astrocytes, oligodendrocytes, and Schwann cells? Microglia and Macroglia. Subtypes of Macroglia: Oligodendrocytes, Schwann cells, Astrocytes. Microglia multiply and metabolize tissue deris. Astrocytes perform housekeeping tasks, deliver glucose, partrol the BBB, and maintain balance (ph and Ionic) between groups of neurons. Oligodendrocytes are myelin forming glia that wrap around multiple axons within the CNS. Schwann cells form myelin around cells in the PNS. One segment per cell. Glial cells are found throughout the CNS and PNS. The three main types of glial cells in the CNS are oligodendrocytes, microglia, and astrocytes.
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3. How are oligodendrocytes and Schwann cells the same and different? They both form myelin around axons, but Oligodendrocytes do so for multiple axons and do their work in the CNS. Schwann cells work on only one segment and do their work in the PNS. Schwann cells myelinate only a single segment of one cell, whereas oligodendrocytes may myelinate several segments of the same axon or several different axons.
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