Purves Neuroscience Website Questions Ch 8 Answers 3c4p

Website Questions by Don O’Malley for Neuroscience, Fifth Edition Chapter 8: Synaptic Plasticity Due Nov 18 (or Nov 20 if lecture extends to Nov 18) 1. Which of the following statements about the plasticity of synapses in the mammalian CNS is false? a. The hallmark of both short-term and long-term synaptic plasticity is that they always increase the strength of synaptic connections. b. The efficacy of synapses can be adjusted by modulating the amount of neurotransmitter that is released. c. Calcium ions play a central role in at least some forms of synaptic plasticity. d. Changes in synaptic efficacy can occur over time scales ranging from milliseconds to years. e. A variety of molecular mechanisms are involved in the different forms of synaptic plasticity. 2. Firing an action potential in an axon initially causes a 10 mV depolarization (EPSP) in a postsynaptic neuron, but after giving a certain stimulus to the axon, firing it causes an 8 mV depolarization, after each action potential. This phenomenon is called a. enhancement. b. depression. c. facilitation. d. augmentation. e. potentiation. 3. After firing a short burst of action potentials in an axon, researchers observe a larger EPSP in the postsynaptic cell, and this effect seems to last a few tens of milliseconds. According to the favored hypothesis for this phenomenon, the presynaptic terminal most likely has _______. a. extra calcium b. lowered calcium c. extra sodium d. reduced sodium e. extra magnesium 4. Which of the following would not be a plausible mechanism explaining synaptic depression? a. Inhibition of presynaptic calcium channels, leading to less calcium influx b. Activation of presynaptic potassium channels, leading to briefer action potentials c. Depletion of docked synaptic vesicles in the presynaptic terminal d. Delayed replenishment of vesicles to the reserve pool e. Enhancement of presynaptic sodium currents 5. Which of the following statements about long-term synaptic plasticity in Aplysia is false? a. The efficacy of transmission at many synapses depends upon their history of synaptic activity. b. The tracking of long-term changes in synaptic efficacy is more difficult in mammalian systems than in Aplysia because of the complexity of mammalian brains. c. The gill withdrawal reflex in Aplysia can be enhanced by means of a noxious stimulus paired with a mild touch. d. Associative learning in the Aplysia gill withdrawal reflex is relatively independent of the timing or the order in which different stimuli are applied. e. Gill withdrawal behavior in Aplysia can be altered for days or weeks by means of repeated pairings of shocks and touches. 6. Which of the following mechanisms contributes to the long-term enhancement of the gill withdrawal reflex in Aplysia but is not involved in the short-term enhancement of the reflex? a. Activation of G-protein-coupled receptors by serotonin b. Phosphorylation of CREB c. Activation of adenylyl cyclase d. Activation of protein kinase A e. Decreased opening of potassium channels during presynaptic action potentials

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7. Learning and memory processes in the fruit fly Drosophila show striking molecular overlap with analogous processes in Aplysia, in of their using all of the following except a. phosphodiesterase. b. adenylyl cyclase. c. adenylyl cyclase activating pathways. d. allosteric modulation of GABAA receptors. e. CREB gene regulation. 8. Which of the following was not an important factor in the discoveries made from the genetic analysis of learning and memory in fruit flies? a. The ability to behaviorally assay large numbers of animals b. Development of an assay that was sensitive to learning and memory deficits c. The ability to discriminate learning deficits from sensory and motor deficits d. Development of novel apparatus to perform the behavioral assays e. All of the above were important. 9. Which of the following is not part of the hippocampus? a. Area CA1 b. Area CA3 c. Area MT d. Dentate gyrus e. None of the above; all are part of the hippocampus 10. Which of the following is the band of hippocampal dendrites that receives inputs from the Schaeffer collaterals? a. Mossy fibers b. Perforant path c. Stratum radiatum d. CA1 region e. CA3 region 11. Which of the following statements about LTP is false? a. LTP involves an enhancement in synaptic efficacy that can last for hours, days, or even weeks. b. If one synapse (A) is very strongly stimulated (sufficient to cause LTP), and another nearby synapse (B) on the same dendrite is weakly stimulated at the same time, then the second synapse (B) will also show LTP. c. If one synapse (A) is very strongly stimulated (sufficient to cause LTP), and a nearby synapse (B) on the same cell is weakly stimulated a few seconds later, then the second synapse (B) will also show LTP. d. The requirement for coincident pre- and post-synaptic activation was predicted by Donald Hebb. e. Hippocampal LTP was first reported by Bliss and Lomo in the 1970s. 12. The type of receptor that is critical for the induction of hippocampal LTP, by virtue of its itting calcium into a dendritic spine, is called a. an AMPA receptor. b. an NMDA receptor. c. a glycine receptor. d. a cholinergic GPCR. e. a noradrenergic GPCR. 13. The key aspect of receptor gating in the associative induction of hippocampal LTP is that a. all glutamate receptors open automatically whenever glutamate is in the synaptic cleft. b. the NMDA receptor acts as a molecular coincidence detector. c. the AMPA receptor allows calcium into the cell only after the NMDA receptor is activated. d. both the GABA and AMPA channels must be open in order for the cell to depolarize. e. All of the above are key aspects of LTP induction.

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14. Which of the following statements about the mechanisms underlying hippocampal LTP induction is false? a. An influx of calcium triggers two or more intracellular processes in the postsynaptic dendritic spine. b. Calcium may trigger the release of a retrograde messenger that enhances transmitter release from the presynaptic terminal. c. Calcium may activate CaM kinase II in such a way that it switches to a long-term “on” state. d. Calcium activates a signaling cascade that causes insertion of glutamate receptors into the postsynaptic membrane. e. Calcium decreases a resting leak current of sodium so that the postsynaptic cell is closer to threshold and therefore fires more easily. 15. Silent synapses are silent because they a. have no presynaptic terminal. b. have AMPA receptors but no NMDA receptors. c. have NMDA receptors but no AMPA receptors. d. lack voltage-gated sodium channels. e. are continuously inhibited and so cannot be activated. Textbook Reference: Box 8B: Silent Synapses 16. Which of the following mechanisms used in hippocampal LTD is not part of the hippocampal LTP mechanism? a. History-dependent modification of synaptic efficacy b. NMDA receptor activation c. Calcium influx d. Calcium-dependent activation of protein phosphatases e. All of the above are used in both LTD and LTP. 17. The targets of the phosphatases activated during hippocampal LTD, other than AMPA receptors, are a. voltage-gated ion channels. b. other ligand-gated ion channels. c. synaptic vesicle regulatory proteins. d. postsynaptic signaling pathways. e. unknown. 18. Cerebellar LTD depends upon a. synergistic actions of calcium and IP3 on internal calcium release channels. b. synergistic actions of sodium and IP3 on internal calcium release channels. c. activation of AMPA receptors by voltage-gated ion channels. d. binding of IP3 to clathrin to activate endocytosis. e. calcium-dependent insertion of GABA receptors into the postsynaptic membrane. 19. Which of the following has been observed regarding the spike timing-dependent plasticity of synapses? a. Whether or not LTP occurs depends on the specific temporal pattern of action potentials and is independent of EPSP temporal pattern. b. LTP occurs whenever an action potential precedes an EPSP. c. LTD occurs whenever an action potential follows an EPSP. d. Switching the relative timing of action potential and EPSP by as little as 15 msec can switch the response from LTD to LTP, or vice versa. e. A rhythmic pattern of spike-EPSP-spike-EPSP, at 40 msec intervals, produces maximal LTP. 20. In the context of neuropathological activity, the phenomenon of kindling refers to a. small burns made in cortex by an electrical stimulating electrode. b. the ability to induce LTP in the amygdala and other brain regions in live animals. c. the ability of daily istration of a single weak pulse to gradually evoke larger and larger behavioral seizure like responses.

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d. the phenomenon whereby a single, strong electrical pulse can evoke a full-blown seizure. e. chaotic patterns of neural activity resembling the flame of a candle.

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