4. The output element is composed of the nerve terminals. They are the transmitting elements of the neuron. One neuron can form contacts with as many as 1000 other neurons. GLIAL CELLS (Fig. 8-5): • In the CNS, glial cells are 10-50 times more numerous than neurons. • Glial cells are implicated in various roles during development and injuries. They are supporting elements. • Glial cells are not implicated in processing of information. • In the CNS, the astrocytes , by far the most numerous of all glial cells, have long and numerous processes, their role is to induce the endothelial cells to form the blood-brain barrier. Some glial cells surround the nerve cell bodies and their axons (Fig. 8-6) : 1. In the CNS, oligodendrocytes are the glial cells that wrap around the axons to insulate them. 2. In the PNS, Schwann cells are the glial cells that insulate the axons by forming a myelin sheath that increases the speed of the electrical conduction. Chapter 8: The nervous system
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