BIPN%20100%20Handout%202_Wk3 - BIPN 100 Handout 2(Week 3...

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BIPN 100 Handout 2 (Week 3) T.A. Marissa (Marlee) Caballes Section: Friday (9:00am - 9:50am) Solis 109 OH: ( 10:00am – 11:00am) Old Student Center ----------------------------------------------------------------------------------------------------------------- I. Conduction is faster in myelinated axons (Figure 8-18) a. The myelin sheath creates a high resistance wall that prevents flow of ions out of the cytoplasm. They increase the thickness by 100-fold. This sheath alternates with section of bare membrane – Nodes of Ranvier , which have a high concentration of Na+ channels which depolarize. Localized depolarization maintains the amplitude of the action potential through the length of the axon as it passes from node to node. The action potential passes along the myelinated segments, so conduction is not slowed by channel opening, since channels only open at the nodes. b. Saltatory conduction is a good alternative to large diameter axons, since in the human body a large size is not practical c. Demyelinating diseases can have adverse effects on neural signaling. It slows the conduction of action potentials. i. Multiple sclerosis is an example. 1. fatigue, muscle weakness, hard to walk, bad vision ii. Tissues of the CNS 1. White matter : myelinated axons and very few cell bodies a. Tracts: bundles of axons in the in the CNS. Equivalent to nerves in the PNS 2. Gray matter: unmyelinated nerve cell bodies, dendrites, axon terminals a. Nuclei: clusters of cell bodies in the CNS II. Glial cells and their functions (Figure 8-5)
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a. Support cells of the nervous system i. Provide structural stability and metabolic support to neurons. ii. Maintain homeostasis of brain’s ECF iii. They communicate by chemical signaling b. PNS i. Schwann (myelin) ii. Satellite c. CNS i. Oligodendrocytes (myelin) ii. Astrocytes – highly branched cells that communicate through gap junctions iii. Microglia – immune cells that remove damaged cells and foreign invaders iv. Ependymal cells III. Cell to cell communication a. Electrical signals from the axon hillock travel to the distal end of the axon where the signal is translated into a chemical signal by the secretion of a neurotransmitter, neuromodulator, or neurohormone.
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BIPN%20100%20Handout%202_Wk3 - BIPN 100 Handout 2(Week 3...

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