BearCh05-ACRQedt - Chapter 05 Synaptic Transmission Answers...

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Chapter 05 – Synaptic Transmission Answers to Chapter Review Questions Page 1 of 4 Copyright © 2007. Lippincott Williams & Wilkins. Ancillary material to accompany Bear et al.: Neuroscience: Exploring the Brain, 3e Question 1: What is meant by quantal release of neurotransmitter? Answer: The elementary unit of a neurotransmitter release is the content of one synaptic vesicle. Each vesicle contains several thousand transmitter molecules. The total amount of transmitter released at a synapse is a multiple of this number, depending on how many vesicles release their contents into the synaptic cleft. The amplitude of postsynaptic EPSP is a multiple of the response to the contents of one vesicle. It reflects the number of transmitter molecules in one synaptic vesicle and the number of postsynaptic receptors available at the synapse. Question 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? Answer: Nicotonic ACh receptors are permeable to both sodium and potassium. When V m = –60 mV, net current flow through ACh-gated ion channels is inward, toward the equilibrium potential of sodium, causing depolarization. At V m = 60 mV, the direction of net current flow through the ACh-gated ion channels is outward, toward the equilibrium potential of potassium, causing the membrane potential to become less positive. The critical value of membrane potential 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. At 0 mV, no current flows. Question 3:
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This note was uploaded on 09/09/2009 for the course SPHSC 449 taught by Professor Peter during the Summer '09 term at University of Washington.

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BearCh05-ACRQedt - Chapter 05 Synaptic Transmission Answers...

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