Review Answers 5 - Review Questions Chapter 5 Answer Key...

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Review Questions Chapter 5 Answer Key From Textbook 1. What is meant by quantal release of neurotransmitter? Neurotransmitter is not released in any amount, but in “packets” (quanta). The elementary unit of neurotransmitter release is the content of one synaptic vesicle. Each vesicle contains about the same number of transmitter molecules. The total amount of transmitter released at a synapse is a multiple of this number. The amplitude of postsynaptic EPSP is therefore a multiple of the response to the contents of a single vesicle. 2. You apply ACh and activate nicotinic receptors on a muscle cell. Which way will current flow through the receptor channels when V m = -60 mV? When V m = 0 mV? When V m = 60 mV? Why? See Box 5.4, p. 120, for an IV-curve of the current through the ACh receptor. Nicotonic ACh receptors are permeable to both sodium and potassium. When Vm = –60 mV, net current flow through ACh-gated ion channels is inward, bringing the membrane potential toward the equilibrium potential of sodium, causing depolarization. At 0 mV, no current flows. At Vm = 60 mV, the direction of net current flow through the ACh-gated ion channels is outward, bringing the membrane potential toward the equilibrium potential of potassium (less positive). The critical value at which the direction of current flow reverses is called the reversal potential. In this case, the reversal potential is 0 mV because this is the value between the equilibrium potentials of sodium and potassium. 3. In this chapter, we discussed a GABA-gated ion channel that is permeable to Cl - . GABA also activates a G-protein-coupled receptor, called the GABA B receptor, which causes potassium-selective channels to open. What effect would GABA B receptor activation have on the membrane potential? The activation of GABA
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This homework help was uploaded on 04/03/2008 for the course CELL BIO & 245 taught by Professor Schjott during the Spring '08 term at Rutgers.

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Review Answers 5 - Review Questions Chapter 5 Answer Key...

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