HW8_17.pdf - Homework#8_Fall 2017 1 Acetylcholine-gated...

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Homework #8_Fall 2017 1 1.Acetylcholine-gated channels cation channels do not discriminate among Na+, K+, and Ca2+ions, allowing all to pass through freely. How is it, then, that when acetylcholine receptors in muscle cells open there is a large net influx principally of Na+? (Hint: look at the distribution of ions in the table below). COMPONENT INTRACELLULAR CONCENTRATION (mM) EXTRACELLULAR CONCENTRATION (mM) CATIONS Na+ 5-15 145 K+ 140 5 Mg2+ 0.5 1-2 Ca2+ 10-4 1-2 H+ 7x10-5(10-7.2M or pH 7.2) 4x10-5(10-7.4M or pH 7.4) ANIONS Cl- 5-15 110 2.When an action potential in a neuron reaches a synapse, calcium is released into the cell, causing release of neurotransmitter into the synaptic cleft. What causes the release of calcium into the cytosol? Explain your answer a. sodium binds to calcium channels in the ER b. the action potential activates adenylate cyclase resulting in higher cAMP levels c. the open sodium channels also allow influx of calcium which is enough to cause neurotransmitter release

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