chapter 11 and 12

chapter 11 and 12 - 11/14 How are action potentials...

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11/14 How are action potentials propagated? In terms of Na+ and K+, what is the cause of an action potential? What happens to the membrane potential when an action potential is created? Why does a depolarized membrane rapidly return to its hyperpolarized state? Compare and contrast action potential propagation along myelinated and unmyelinated axons. REVIEW of skeletal muscle function.
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When excitable cells (neurons and myofibers) are at rest they have lots of potassium on the inside and lots of sodium outside of the cell. They exhibit excitability when Na+ and/or K+ suddenly move across the plasma membrane through special channels that open for this specific purpose! These channels continue this process along the length of the membrane.
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An action potential occurs when a depolarization is initiated and propagates itself down the length of a neuron or muscle cell. Step One : Something initiates local depolarization (generator potential) Damage Ligand-gated ion channels are often opened by acetylcholine or other neurotransmitter compounds (ligand): I.E. the neuromuscular junction Stretch/Mechano receptors (ion channels): Cells in the ear work this way Leaking ions passing through gap junctions: Cardiac cells work this way Step Two : Voltage gated channels detect a local change in membrane potential that was created (step 1) and each VG-Na+ channel stays open for only a a few microseconds (Na+) then closes! Step Three : Other neighboring voltage gated Na+ channels open
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Could you discuss what happens during the 7 steps shown above? What causes hyperpolarization above at step #6?
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chapter 11 and 12 - 11/14 How are action potentials...

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