Module 3 Chapter 17 Multiple choice questions 17.4

. What is the approximate duration of a typical action potential, from initiation to a stable return to resting membrane potential?

1 ms

3 ms

5 ms

10 ms

. The α-subunit of voltage-gated sodium channels contains four domains, each comprising six transmembrane helices. How does the α-subunit of voltage-gated sodium channels control sodium movement through the cell membrane?

The S1-4 helices form the channel pore and the S5-6 helices are part of the voltage-sensor. The link between domains 1 and 2 forms the inactivation gate.

The S1-4 helices form the channel pore and the S5-6 helices are part of the voltage-sensor. The link between domains 3 and 3 forms the inactivation gate.

The S1-4 helices form the voltage-sensor and the S5-6 helices are part of the channel pore. The link between domains 1 and 2 forms the inactivation gate.

The S1-4 helices form the voltage-sensor and the S5-6 helices are part of the channel pore. The link between domains 3 and 4 forms the inactivation gate.

. By what percentage is the total number of sodium ions (Na⁺) inside an axon estimated to change due to sodium ion influx during an action potential?

0.05%

0.5%

5%

50%

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