Chp 5 Test bank

15. If the distribution of EPP amplitudes has peaks at 0.4 mV, 0.8 mV, 1.2 mV, 1.6 mV, and 2.0 mV, what is the most likely amplitude of the MEPP? a. 0.4 mV b. 0.8 mV c. 1.2 mV d. 1.6 mV e. 2.0 mV

a. 0.4 mV

4. Which substances diffuse through connexon channels between pre- and postsynaptic neurons? a. Ions b. Second messengers c. Small proteins d. ATP e. All of the above

e. All of the above

10. You conduct a voltage clamp experiment in which you hold the presynaptic terminal of a glutamatergic neuron (a neuron that releases glutamate) at 0 mV. When you treat the terminal with TTX, an inward current is recorded. Which ion and ion channels are responsible for the current you observe? a. Calcium; voltage-gated calcium channels b. Sodium; voltage-gated sodium channels c. Potassium; voltage-gated potassium channels d. Calcium; ligand-gated non-specific cation channels e. Sodium; ligand-gated non-specific cation channels

a. Calcium; voltage-gated calcium channels

5. A scientist wishes to develop a new drug that prevents synaptic communication via neuropeptides but not small molecule neurotransmitters. Which mechanism would be a good target for his drug? a. Disruption of axonal transport b. Blocking of voltage-gated calcium channels c. Disruption of V-SNARES d. Blocking of voltage-gated sodium channels e. Increasing levels of synaptotagmin

a. Disruption of axonal transport

6. What is the action of the neurotransmitter at a chemical synapse? a. It acts on receptors in the postsynaptic membrane. b. It electrically activates the presynaptic neuron. c. It crosses the postsynaptic membrane and then activates ion channels in the postsynaptic neuron. d. It depolarizes the postsynaptic membrane by delivering an electrical charge. e. It transfers an action potential from the presynaptic neuron to the postsynaptic neuron.

a. It acts on receptors in the postsynaptic membrane.

13. In an experiment on an animal model in which the synapsin gene is knocked out, you measure the density of synaptic vesicles in the presynaptic terminal within the active zone and outside the active zone in both knockout and control animals. Given what you know about the function of synapsin, what would you expect to find? a. There will be fewer vesicles in the reserve pool in knockout animals than in controls. b. There will be more vesicles in the reserve pool in knockout animals than in controls. c. There will be no vesicles in the presynaptic terminal in knockout animals. d. There will be no vesicles docked in the active zone in knockout animals. e. There will be no difference between knockout animals and controls.

a. There will be fewer vesicles in the reserve pool in knockout animals than in controls.

21. At -10 mV, end plate current is _______ in amplitude and directed _______. a. small; inward b. small; outward c. large; inward d. large; outward e. None of the above

a. small; inward

3. Listed below are the individual events that make up chemical synaptic transmission. 1. Diffusion of transmitter across the synaptic cleft 2. Depolarization of the presynaptic terminal 3. Vesicle fusion with plasma membrane 4. Opening of voltage-gated ion channels 5. Activation of presynaptic, calcium-sensitive proteins Which sequence represents the correct ordering of these events? a. 1; 2; 3; 4; 5 b. 2; 4; 5; 3; 1 c. 2; 5; 4; 3; 1 d. 5; 4; 2; 3; 1 e. 1; 2; 4; 5; 3

b. 2; 4; 5; 3; 1

20. Which protein plays a key role in endocytosis? a. Auxilin b. Clathrin c. Triskelion d. Actin e. Hsc70

b. Clathrin

16. What is the source of the quanta that make up the EPP? a. Pulses of current that flow through the electrical synapse b. Fusion of individual synaptic vesicles with the plasma membrane c. Individual action potentials d. Current through a single ion channel e. Short-term increases in membrane permeability

b. Fusion of individual synaptic vesicles with the plasma membrane

The figure shows an electron micrograph of a chemical synapse in the cerebral cortex. Which statement about this synapse is accurate? a. Inside the postsynaptic neuron are synaptic vesicles, which fuse with the membrane in the postsynaptic density. b. Inside the presynaptic neuron are synaptic vesicles, which fuse with the membrane in the active zone. c. Inside the presynaptic neuron are synaptic vesicles, which fuse with the membrane in the postsynaptic density. d. A gap junction connects the two neurons via connexons that span the pre- and postsynaptic membranes. e. None of the above

b. Inside the presynaptic neuron are synaptic vesicles, which fuse with the membrane in the active zone.

16. Which statement regarding metabotropic and ionotropic receptors is true? a. Metabotropic receptors open channels faster than ionotropic receptors do. b. Ionotropic receptors have immediate effects; metabotropic receptors produce long-term effects. c. Both directly allow ion flow through an ion pore in the receptor. d. Metabotropic and ionotropic receptors act via the same mechanisms; the difference is the neurotransmitters that activate them. e. Ionotropic receptors require the activation of intracellular messengers.

b. Ionotropic receptors have immediate effects; metabotropic receptors produce long-term effects.

11. Which researcher(s) proved that chemicals transfer electrical information between neurons? a. Rod MacKinnon b. Otto Loewi c. Jens Christian Skou d. Richard Keynes e. Alan Hodgkin and Andrew Huxley

b. Otto Loewi

18. When a muscle fiber is held at a voltage of 0 mV at the neuromuscular end plate, acetylcholine no longer produces a current because a. the acetylcholine receptor channels all close instantly at 0 mV. b. an influx of sodium is balanced by an equal efflux of potassium. c. the membrane conductance for each permeant ion is 0 at 0 mV. d. at 0 mV, the potassium ions lodge in the receptor channel and block the influx of sodium. e. the Nernst potentials for both sodium and potassium are 0 mV in muscle fibers.

b. an influx of sodium is balanced by an equal efflux of potassium.

15. Black widow spider venom is thought to disrupt the functioning of nerve terminals by a. proteolytic cleavage of SNARE proteins. b. circumventing the calcium-regulated step of exocytosis to promote massive exocytosis. c. binding to all molecules of synapsin, synaptotagmin, and synaptophysin, thereby preventing their normal functioning. d. punching holes in vesicles, thereby causing release of their contents into the cytosol. e. blocking calcium channels.

b. circumventing the calcium-regulated step of exocytosis to promote massive exocytosis.

2. The capability of a nerve terminal to rapidly and dramatically produce very large changes in calcium levels is most dependent on the a. presence of calcium-selective ion channels. b. enormous gradient of calcium across the membrane. c. fact that calcium is a positively charged ion. d. fact that calcium is a divalent cation. e. All of the above are essential for producing large, rapid concentration changes.

b. enormous gradient of calcium across the membrane.

14. Small-molecule neurotransmitters are _______ for _______. a. taken back into the presynaptic terminal; degradation b. taken back into the presynaptic terminal; reuse c. taken up by the postsynaptic cell; degredation d. taken up by the postsynaptic cell; reuse e. scattered in the synaptic cleft; reuse

b. taken back into the presynaptic terminal; reuse

5. Which feature of an electrical synapse allows synchronizing the electrical activity of multiple neurons? a. Fast speed of transmission b. Ability of neurons to form gap junctions with glial cells c. Bidirectional transmission of electrical signals d. Slow transmission of signals e. Bidirectional transmission of chemical signals

c. Bidirectional transmission of electrical signals

1. Which structure can be found exclusively at an electrical synapse? a. Synaptic cleft b. Synaptic vesicle c. Connexon d. Neurotransmitter receptor e. Presynaptic membrane

c. Connexon

7. Which event is the first in the series of events that take place during chemical synaptic transmission? a. Neurotransmitter binds to its receptors. b. Influx of Ca2+ in the presynaptic terminal. c. Voltage-gated Ca2+ channels open. d. Neurotransmitter is released into the synaptic cleft. e. Synaptic vesicles fuse with the presynaptic membrane

c. Voltage-gated Ca2+ channels open.

2. Presynaptic and postsynaptic neurons that form _______ synapses are connected via _______. a. chemical; connexons b. chemical; neurotransmitter release c. electrical; gap junctions d. electrical; the synaptic cleft e. electrical; synaptic vesicles

c. electrical; gap junctions

11. SNARE proteins participate in vesicle exocytosis by a. forming a protein coat that maintains the vesicle's integrity. b. binding calcium and then forming a pore into the vesicle. c. forming a protein complex that pulls the vesicle membrane against the plasma membrane. d. linking calcium channels to exocytotic fusion sites. e. pushing vesicles from the reserve pool into the docked pool.

c. forming a protein complex that pulls the vesicle membrane against the plasma membrane.

14. The decrease in size of individual quanta observed in familial infantile myasthenia is consistent with the observation of a. fewer calcium channels in the presynaptic terminals compared with healthy controls. b. a greater rate of spontaneous exocytosis depleting the size of the vesicle pool, than in healthy controls. c. smaller synaptic vesicles compared with healthy controls. d. a change in the sensitivity of the calcium release mechanism compared with healthy controls. e. a loss of all ACh receptors at the neuromuscular junction.

c. smaller synaptic vesicles compared with healthy controls.

19. The most important factor determining whether a receptor-operated ion channel is inhibitory or excitatory is a. the ligand-binding properties of the receptor. b. whether the permeant ion is positively or negatively charged. c. whether the permeant ion's reversal potential is positive or negative to threshold. d. the number of different ions that can pass through the receptor. e. None of the above

c. whether the permeant ion's reversal potential is positive or negative to threshold.

3. How many connexin subunits form one complete synaptic channel? a. 4 b. 6 c. 10 d. 12 e. 16

d. 12

12. Which treatment would prevent the release of neurotransmitter from the presynaptic terminal? a. Potassium channel blocker b. Acetylcholinesterase c. Monoamine oxidase inhibitor d. A toxin that cleaves synaptobrevin e. AMPA antagonist

d. A toxin that cleaves synaptobrevin

4. Which characteristic is an accepted criterion for classifying a molecule as a neurotransmitter? a. It must be present in the presynaptic terminal. b. It must be released in response to presynaptic electrical activity. c. It must exert an effect on the postsynaptic cell. d. All of the above e. None of the above

d. All of the above

8. At which point during signal transmission at a chemical synapse is exocytosis occurring? a. As neurotransmitter binds to its receptors b. While Ca2+ enters the presynaptic terminal c. As voltage-gated Ca2+ channels are opening d. During neurotransmitter release into the synaptic cleft e. During reuptake, as synaptic vesicles are reformed from the plasma membrane

d. During neurotransmitter release into the synaptic cleft

10. In the sequence of events in neurotransmission, which event occurs just after the action potential arrives at the presynaptic terminal? a. Packaging of the neurotransmitter b. Delivery of the neurotransmitter to the presynaptic terminal c. Fusion of the synaptic vesicles with the presynaptic membrane d. Influx of Ca2+ into the presynaptic terminal e. Release of the neurotransmitter

d. Influx of Ca2+ into the presynaptic terminal

18. How would application of an intracellular Ca2+ chelator affect the function of a synapse? a. It would increase the magnitude of postsynaptic potential. b. It would decrease the magnitude of postsynaptic potential. c. It would eliminate the postsynaptic potential but have no effect on presynaptic potential. d. It would eliminate the postsynaptic potential and Ca2+-dependent vesicle fusion. e. It would eliminate the presynaptic Ca2+ current but have no effect on the postsynaptic potential.

d. It would eliminate the postsynaptic potential and Ca2+-dependent vesicle fusion.

17. How would application of a Ca2+ channel blocker affect the function of a synapse? a. It would increase the magnitude of postsynaptic potential. b. It would decrease the magnitude of postsynaptic potential. c. It would eliminate the postsynaptic potential but have no effect on presynaptic neuron. d. It would eliminate the postsynaptic potential and the presynaptic Ca2+ current. e. It would eliminate the presynaptic Ca2+ current but have no effect on the postsynaptic potential.

d. It would eliminate the postsynaptic potential and the presynaptic Ca2+ current.

13. Which vesicles, loaded with neuropeptides, arrive in the presynaptic terminal via axonal transport? a. Small clear-core vesicles b. Large clear-core vesicles c. Small dense-core vesicles d. Large dense-core vesicles e. Synaptic vesicles

d. Large dense-core vesicles

12. Which step of peptide neurotransmitter processing takes place in the presynaptic terminal? a. Synthesis b. Packaging c. Transport d. Release e. Degradation

d. Release

20. Which statement about EPSPs in the central nervous system is true? a. They are much larger than end plate potentials. b. the istance between inputs does not affect the ability of EPSPs to summate c. the time between inputs does not affect the ability of EPSPs to summate d. Their effect in the central nervous system can be nullified by IPSPs. e. They can be hyperpolarizing.

d. Their effect in the central nervous system can be nullified by IPSPs.

1. Gap junctions may exhibit all of the following features except a. the ability to pass small metabolites, including some second messengers. b. the ability to pass electrical current bidirectionally. c. the ability to pass electrical current unidirectionally. d. the ability to amplify small incoming electrical signals into large regenerative potentials. e. the ability to synchronize the activity of populations of nerve cells.

d. the ability to amplify small incoming electrical signals into large regenerative potentials.

9. Which observation would indicate a role for calcium in transmitter secretion? a. Observation of presynaptic depolarizing currents after blockade of sodium channels b. Voltage clamp experiments showing voltage-gated calcium channels in the presynaptic terminal c. Induction of transmitter release by injection of calcium into the presynaptic terminal d. Blockade of transmitter release by injection of calcium blocker into the presynaptic terminal e. All of the above

e. All of the above

19. By which proposed molecular mechanism does Ca2+ promote fusion of synaptic vesicles? a. By binding to synapsin b. By binding SNARE proteins to the complex formation c. By binding to SNARE proteins after the complex formation d. By binding to synaptotagmin and promoting formation of the SNARE complex, which facilitates fusion e. By binding to and inducing changes in synaptotagmin that cause the plasma membrane to curve, facilitating fusion

e. By binding to and inducing changes in synaptotagmin that cause the plasma membrane to curve, facilitating fusion

8. The recycling of synaptic vesicles is tracked using HRP as a vesicle marker. What will be the observed sequence of HRP movement? a. Endosome, coated vesicle, vesicle reserve pool b. Vesicle reserve pool, coated vesicle, endosome c. Endosome, vesicle reserve pool, coated vesicle d. Coated vesicle, vesicle reserve pool, endosome e. Coated vesicle, endosome, vesicle reserve pool

e. Coated vesicle, endosome, vesicle reserve pool

17. Which statement about postsynaptic currents at the neuromuscular end plate is false? a. Depolarizing currents can be recorded from outside-out patches of the postsynaptic membrane. b. Individual channels tend to stay open for no more than a few milliseconds. c. Acetylcholine can induce openings of ligand-gated ion channels. d. The end plate potential is due to the opening of thousands or millions of channels. e. The end plate channels show a regenerative opening pattern that propagates an action potential along the length of the muscle fiber.

e. The end plate channels show a regenerative opening pattern that propagates an action potential along the length of the muscle fiber.

7. To date, which observation is not part of the experimental evidence favoring the vesicular release hypothesis of neurotransmission? a. Fixed size of MEPPs b. Quantized distribution of events occurring at the neuromuscular junction c. Visualization of synaptic vesicles using electron microscopy d. Correspondence between a vesicle's acetylcholine content and MEPP size e. Visualization of acetylcholine molecules diffusing out of the neck of the membrane-fused vesicle

e. Visualization of acetylcholine molecules diffusing out of the neck of the membrane-fused vesicle

6. Miniature end plate potentials, or MEPPs, are produced a. at miniature end plates. b. by the smallest axons. c. in response to weak stimuli. d. by the smallest neurotransmitters. e. by spontaneous release of neurotransmitter.

e. by spontaneous release of neurotransmitter.