Chapter 4 The Action Potential
1. How long does an action potential last from the beginning of the rising phase to the end
of the falling phase? Choose the correct option.
A) 2 nanoseconds
B) 2 msec
C) 2 seconds
D) 2 microseconds
2. What is meant by the action potential threshold? Choose the correct option.
A) Critical level of depolarization required to trigger an action potential
B) Critical level of hyperpolarization required to trigger an action potential
C) The action potential threshold is the same as the generator potential.
D) Critical level at which electrical current is injected through a microelectrode
3. What is the absolute refractory period? Choose the correct option.
A) The period when the firing frequency is at about 1000 Hz
B) The time period of about 1 msec after an action potential before another one can be
initiated
C) The time period of several milliseconds when it is difficult to initiate another action
potential due to sodium channel inactivation
D) The time period when the membrane potential stays hyperpolarized until the
voltage-gated potassium channels close
4. The movement of what ion occurs in the rising phase of the action potential? Choose
the correct option.
A) Inward Na'
B) Outward K
C) Outward Na'
D) Inward K
5. How does the sodium channel selectivity filter differentiate between Na" and K ions?
Choose the correct option.
A) The sodium channel identifies K ions as having the wrong charge.
B) The Kions are stripped of all their water molecules, but the Na ions are not.
C) The sodium channel admits a Na water complex, with the water serving as
a molecular chaperone through the channel.
D) K ions are excluded by voltage gating.
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1. How long does an action potential last from the beginning of the rising phase to the end
of the falling phase? Choose the correct option.
A) 2 nanoseconds
B) 2 msec
C) 2 seconds
D) 2 microseconds
2. What is meant by the action potential threshold? Choose the correct option.
A) Critical level of depolarization required to trigger an action potential
B) Critical level of hyperpolarization required to trigger an action potential
C) The action potential threshold is the same as the generator potential.
D) Critical level at which electrical current is injected through a microelectrode
3. What is the absolute refractory period? Choose the correct option.
A) The period when the firing frequency is at about 1000 Hz
B) The time period of about 1 msec after an action potential before another one can be
initiated
C) The time period of several milliseconds when it is difficult to initiate another action
potential due to sodium channel inactivation
D) The time period when the membrane potential stays hyperpolarized until the
voltage-gated potassium channels close
4. The movement of what ion occurs in the rising phase of the action potential? Choose
the correct option.
A) Inward Na'
B) Outward K
C) Outward Na'
D) Inward K
5. How does the sodium channel selectivity filter differentiate between Na" and K ions?
Choose the correct option.
A) The sodium channel identifies K ions as having the wrong charge.
B) The Kions are stripped of all their water molecules, but the Na ions are not.
C) The sodium channel admits a Na water complex, with the water serving as
a molecular chaperone through the channel.
D) K ions are excluded by voltage gating.
, Page 1
