Q: Which of the following best describes the role of voltage-gated Na\textsuperscript{+} channels during the depolarization phase of an action potential in a neuron?

They open quickly, allowing rapid Na\textsuperscript{+} influx and causing a sharp depolarization.

Q: During the repolarization phase of an action potential, which ion movement is primarily responsible for returning the membrane potential toward its resting value?

Efflux of K\textsuperscript{+} ions

Question 1

Which of the following best describes the role of voltage-gated Na	extsuperscript{+} channels during the depolarization phase of an action potential in a neuron?

Accepted Answer

They open quickly, allowing rapid Na	extsuperscript{+} influx and causing a sharp depolarization.

Question 2

A neuron is stimulated and its membrane potential rises from $$-70\ \mathrm{mV} to$$ $$-55\ \mathrm{mV}. $$What is the significance of $$-55\ \mathrm{mV} in $$the context of action potential generation?

Accepted Answer

It is the threshold potential required to open voltage-gated ion channels.

Question 3

During the repolarization phase of an action potential, which ion movement is primarily responsible for returning the membrane potential toward its resting value?

Accepted Answer

Efflux of K	extsuperscript{+} ions

Question 4

Which statement best explains why action potentials only travel in one direction along an axon?

Accepted Answer

The absolute refractory period prevents the backward propagation of action potentials.

Question 5

A patient has a genetic mutation that slows the closing of voltage-gated K	extsuperscript{+} channels in neurons. What effect would this most likely have on the action potential?

Accepted Answer

It would result in a longer hyperpolarization phase after the action potential.

Question 6

Which of the following best describes the 'all-or-none' law of action potentials?

Accepted Answer

Once threshold is reached, an action potential of maximum amplitude is always generated.

Question 7

What is the primary difference between continuous and saltatory propagation of action potentials?

Accepted Answer

Saltatory propagation involves action potentials jumping between nodes of Ranvier, increasing speed and efficiency.

Question 8

If the diameter of an axon increases, what effect does this have on the speed of action potential propagation, and why?

Accepted Answer

Speed increases because larger diameter reduces internal resistance.

Question 9

Which phase of the action potential is characterized by the membrane potential becoming more negative than the resting membrane potential?

Accepted Answer

Hyperpolarization

Question 10

A toxin blocks voltage-gated Na	extsuperscript{+} channels in neurons. What would be the immediate effect on the generation of action potentials?

Accepted Answer

Action potentials would fail to initiate due to lack of depolarization.

Question 11

Which of the following best explains why myelinated axons conduct action potentials faster than unmyelinated axons?

Accepted Answer

Myelin allows the action potential to jump between nodes of Ranvier, reducing the number of membrane segments that must depolarize.

Question 12

During which period is it impossible for a neuron to fire another action potential, regardless of stimulus strength?

Accepted Answer

Absolute refractory period

Question 13

Which of the following events occurs LAST during the generation of an action potential?

Accepted Answer

Return to resting membrane potential

Question 14

A neuron is exposed to a drug that increases the permeability of the membrane to K	extsuperscript{+} ions during the repolarization phase. What is the most likely effect?

Accepted Answer

The neuron will repolarize more quickly and may experience a deeper hyperpolarization.

Question 15

Which of the following is TRUE regarding graded (local) potentials and action potentials?

Accepted Answer

Graded potentials decrease in strength as they spread, while action potentials maintain their amplitude.

Question 16

Which equation best represents the change in membrane potential during the depolarization phase of an action potential?

Accepted Answer

$$V_{m} = V_{rest} + \Delta V_{Na$$^{+}$$}$$

Question 17

Which of the following is a direct consequence of the absolute refractory period in neurons?

Accepted Answer

Action potentials only travel in one direction along the axon.

Question 18

A nerve cell is at rest with a membrane potential of $$-70\ \mathrm{mV}. $$Which of the following best describes the distribution of ions across the membrane at this state?

Accepted Answer

High Na	extsuperscript{+} outside, high K	extsuperscript{+} inside

Question 19

Which of the following would most likely increase the energy efficiency of action potential propagation in a neuron?

Accepted Answer

Increasing myelination, promoting saltatory conduction

Cellular Electricity and Action Potentials in Excitable Cells

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