Practice Questions: Cell Physiology
1. An important feature of the leakage K+ channels that generate the resting membrane potential in neurons is that
A. they take approximately 200 msec to gate open.
B. they have a high probability of being open at the resting membrane potential.
C. they open only when the membrane potential is depolarized to voltages more positive than 0 mV.
D. they inactivate very rapidly after they open.
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2. On the planet Endor, animals have evolved a unique nervous system. Neurons in these animals are exclusively permeable to Ba2+ at their normal resting membrane potential. In these animals, there is a 10-fold higher Ba2+ concentration outside the cell than there is inside. The resting membrane potential of these cells will be approximately
A. –58 mV.
B. –29 mV.
C. 0 mV.
D. +29 mV
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3. From a functional standpoint, Na+ channel inactivation is important because
A. inactivation allows a neuron to depolarize rapidly during the rising phase of the action potential.
B. inactivation allows a neuron to repolarize rapidly once the peak of the action potential has been reached.
C. inactivation contributes to the stretch-sensitivity of Na+ channels.
D. A and B only
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4. In patients with Lambert-Eaton myasthenic syndrome, Ca2+ channel function in presynaptic terminals is disrupted. If you recorded postsynaptic miniature endplate potentials (mEPPs) in biopsy samples from these patients, the potentials
A. would have a smaller-than-normal amplitude.
B. would have a normal amplitude.
C. would have a larger-than-normal amplitude.
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5. A miniature endplate potential (mEPP) is generated by
A. one molecule of acetylcholine released into the synaptic cleft.
B. the acetylcholine contained in one synaptic vesicle released into the synaptic cleft.
C. the acetylcholine contained in approximately 150 synaptic vesicles released into the synaptic cleft.
D. an action potential arriving at the endplate.
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6. Which of the following ionotropic receptor types is highly permeable to sodium ions?
A. GABA-A receptor
B. nicotinic acetylcholine receptor
C. AMPA receptor
D. NMDA receptor
E. more than one of the above
Answer : E
7. On the planet Klingon, neurons at rest are permeable to both K+ and Na+, due to the presence of voltage-independent (leakage) K+ and Na+ channels. Assume the following ion concentrations: K+ inside, 100 mM; K+ outside, 10 mM; Na+ inside 10 mM; Na+ outside 100 mM. Assume that the permeability of single K+ and Na+ channels are equal. If five times as many K+ channels as Na+ channels are open, the membrane potential of Klingon neurons will be approximately
A. -31 mV.
B. 0 mV.
C. +31 mV.
D. +58 mV.
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8. The primary factor that controls the resting membrane potential of neurons is
A. Na+ channels are inactivated at rest.
B. low voltage-activated Ca2+ channels are open at rest.
C. leakage K+ channels are open at rest.
D. Cl- channels are open at rest.
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9. The presence of external Ca2+ is essential for chemical synaptic transmission because
A. Ca2+ is needed to activate ligand-gated receptors on the postsynaptic membrane.
B. Ca2+ influx into the presynaptic terminal is needed for the release of neurotransmitter.
C. Ca2+ influx is required to depolarize the presynaptic terminal.
D. A and B
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10. Which ionotropic receptor is highly permeable to calcium ions?
A. GABAA receptor
B. AMPA receptor
C. NMDA receptor
D. B and C
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11. Which of the following statements regarding the NMDA receptor is FALSE?
A. The glutamate binding site is part of the receptor.
B. It has a cation selective ion pore.
C. It generates fast EPSPs in many synapses.
D. It is blocked by calcium ions in the resting cell.
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12. Which of the following is NOT an ionotropic receptor?
A. GABA-B receptor
B. NMDA receptor
C. glycine receptor
D. nicotinic acetylcholine receptor
E. AMPA receptor
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13. A miniature endplate potential (MEPP) is generated by:
A. one molecule of acetylcholine released into the synaptic cleft.
B. the acetylcholine contained in one synaptic vesicle released into the synaptic cleft.
C. the acetylcholine contained in approximately 150 synaptic vesicles released into the synaptic cleft.
D. an action potential arriving at the endplate.
E. none of the above.
Answer :
14. The primary factor that controls the resting membrane potential of neurons is:
A. Na+ channels are inactivated at rest.
B. low voltage-activated Ca2+ channels are open at rest.
C. leakage K+ channels are open at rest.
D. Cl- channels are open at rest.
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15. If the number of open ion channels in a dendrite DECREASES, the membrane length constant will:
A. be shorter.
B. remain the same.
C. be longer.
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16. Which of the following is a property of the NMDA receptor?
A. It couples to G-proteins.
B. It contains a potassium selective ion pore.
C. It generates fast IPSPs in many synapses.
D. It is blocked by calcium ions at hyperpolarized membrane potentials.
E. none of the above
Answer: E
17. Which of the following is defined as the flow of electrons from a region of high negative charge to a region of low negative charge?
A. voltage
B. amperage
C. resistance
D. current
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18. If potassium channels are blocked, the influence on graded potentials will be:
A. less hyperpolarization.
B. more hyperpolarization.
C. less depolarization.
D. no effect.
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19. When a neuron is resting which of the following is the correct distribution of ions inside and outside of its membrane?
A. large protein molecules and chloride ions outside, potassium and sodium ions inside
B. potassium ions and large protein molecules inside, sodium and chloride ions outside
C. potassium and chloride ions inside, large protein molecules and sodium ions outside
D. sodium and chloride ions inside, potassium ions and large protein molecules outside
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20. What is the term used to describe the condition of a neuron in which its axon in the later phase of an action potential during which increased electrical current is required to produce another action potential?
A. partially inhibited
B. relatively disinhibited
C. disequilibriated
D. relatively refractory
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21. Which of the following statements regarding postsynaptic potentials is correct?
A. IPSPs are the result of influx of potassium ions and EPSPs are the result of efflux of sodium ions.
B. IPSPs are the result of efflux of potassium ions and EPSPs are the result of influx of sodium ions.
C. IPSPs are the result of efflux of chloride ions and EPSPs are the result of efflux of calcium ions.
D. IPSPs are the result of efflux of potassium ions and EPSPs are the result of influx of chloride ions.
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22. Temporal summation refers to:
A. summation of action potentials in the temporal cortex.
B. summation of postsynaptic potentials in the temporal cortex.
C. summation of postsynaptic potentials at different places on a neuron at the same time.
D. summation of postsynaptic potentials on a neuron occurring closely together in time.
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23. What neurotransmitter is released at the motor neuron-muscular junction?
a). norepinephrine
b). acetylcholine
c). serotonin
d). dopamine
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