Each voltage-gated Na+ ion channel has two voltage sensitive gates: an activation gate and an inactivation gate. Which of the following would occur during depolarization?
A. Activation gates are open; inactivation gates are closed.
B. Activation gates are closed; inactivation gates are open.
C. Both activation and inactivation gates are open.
D. Both activation and inactivation gates are closed.
E. None of these events occurs during depolarization.
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Question 2) The absolute refractory period ends when
A. inactivation gates of voltage-gated Na+ ion channels reopen.
B. activation gates of voltage-gates Na+ ion channels reopen.
C. the sodium-potassium exchange pump stops.
D. voltage-gated K+ channels open.
E. None of these choices is correct.
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Question 3) In some cells, an afterpotential occurs because
A. the sodium ions continue to enter the cell after depolarization is finished.
B. there is prolonged, elevated permeability to potassium during repolarization.
C. the sodium-potassium pump is actively exchanging ions across the membrane.
D. the extracellular Na+ ion concentration is reduced.
E. the permeability to sodium continues longer than necessary.
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Question 4) During depolarization of the plasma membrane,
A. sodium ions move rapidly into the cell.
B. potassium ions move rapidly out of the cell.
C. membrane permeability to sodium ions decreases.
D. the outside of the cell becomes positively charged relative to the inside.
E. sodium ions move rapidly out of the cell.
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Question 5) The opening of more and more Na+ ion channels during depolarization
A. is the result of the sodium-potassium exchange pump.
B. is an example of a positive feedback cycle.
C. is possible only if K+ channels remain closed.
D. is the cause of the afterpotential.
E. is an example of a negative feedback cycle.
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Question 6) When repolarization of a neuron is complete, the
A. neuron dies.
B. neuron regenerates.
C. cell no longer has a potential difference across its membrane.
D. original polarity of the neuron is restored.
E. neuron is no longer excitable.
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Question 7) Which of the following statements regarding voltage-gated K+ channels is true?
A. These channels have only one gate.
B. These channels open more slowly than Na+ channels.
C. Once open, these channels remain open until repolarization is complete.
D. These channels are specific for potassium.
E. All of these statements are true.
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Question 8) Low levels of ___ can have dire consequences on the functioning of neurons because of its role in membrane repolarization.
A.
sodium ions
B.
potassium ions
C.
chloride ions
D.
hydrogen ions
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Question 9) Depolarization of the nerve cell membrane occurs when there is a rapid influx (inflow) of
A. potassium ions.
B. chloride ions.
C. calcium ions.
D. sodium ions.
E. proteins.
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Question 10) Which of the following events is NOT a characteristic of an action potential?
A. The plasma membrane becomes highly permeable to sodium ions and depolarization results.
B. As sodium ions enter, the inside of the plasma membrane becomes more negative.
C. At the peak of depolarization, sodium channels begin to close and potassium channels open.
D. In repolarization, potassium ions flow out of the cell.
E. Action potentials occur according to the all-or-none principle.
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