Q: Which equation can be used to calculate the equilibrium potential for potassium ($$\mathrm{K^+}) $$ions across the membrane?

$$E_{K^+} = \frac{RT}{zF} \ln \left( \frac{[K^+]_{\text{outside}}}{[K^+]_{\text{inside}}} \right)$$

Question 1

During which phase of the action potential are voltage-gated sodium ($$\mathrm{Na^+}) $$channels open and voltage-gated potassium ($$\mathrm{K^+}) $$channels still closed?

Accepted Answer

Depolarization phase

Question 2

A medication blocks voltage-gated potassium ($$\mathrm{K^+}) $$channels. Which phase of the action potential would be MOST affected?

Accepted Answer

Repolarization phase

Question 3

At the peak of an action potential, the electrical gradient forces potassium ($$\mathrm{K^+}) $$ions:

Accepted Answer

Out of the cell

Question 4

What happens when the neuron reaches threshold (approximately $$-55\ \mathrm{mV}$$)?

Accepted Answer

Voltage-gated sodium channels open and sodium rushes into the cell

Question 5

Which of the following best describes the sequence of events during an action potential?

Accepted Answer

Resting potential → Depolarization → Threshold → Repolarization → Hyperpolarization → Return to resting potential

Question 6

If a neuron is exposed to a toxin that keeps voltage-gated sodium ($$\mathrm{Na^+}) $$channels open, what would most likely happen to the membrane potential?

Accepted Answer

The membrane potential would remain depolarized and fail to repolarize

Question 7

Which ion movement is primarily responsible for the repolarization phase of the action potential?

Accepted Answer

$$\mathrm{K^+}$$ ions moving out of the cell

Question 8

A neuron is at rest with a membrane potential of $$-70\ \mathrm{mV}. $$What maintains this resting potential?

Accepted Answer

The sodium-potassium pump actively transports $$3\ \mathrm{Na^+}$$ out and $$2\ \mathrm{K^+} in$$

Question 9

During hyperpolarization, the membrane potential becomes more negative than the resting potential. Which channel state is most responsible for this?

Accepted Answer

Delayed closing of voltage-gated potassium channels

Question 10

A patient is given a drug that prevents sodium ($$\mathrm{Na^+}) $$channels from opening. What is the most likely effect on the action potential?

Accepted Answer

The neuron will not depolarize and no action potential will be generated

Question 11

Which of the following best explains why the action potential is unidirectional along the axon?

Accepted Answer

The refractory period prevents backward propagation

Question 12

If the extracellular concentration of potassium ($$\mathrm{K^+}) $$increases significantly, what effect would this have on the resting membrane potential?

Accepted Answer

The resting membrane potential would become less negative (depolarize)

Question 13

Which equation can be used to calculate the equilibrium potential for potassium ($$\mathrm{K^+}) $$ions across the membrane?

Accepted Answer

$$E_{K^+} = \frac{RT}{zF} \ln \left( \frac{[K^+]_{	ext{outside}}}{[K^+]_{	ext{inside}}} ight)$$

Question 14

A neuron is exposed to a drug that increases the permeability of the membrane to sodium ($$\mathrm{Na^+}) $$ions at rest. What is the most likely effect?

Accepted Answer

The resting membrane potential will become less negative (depolarize)

Question 15

Which of the following is TRUE regarding the sodium-potassium pump?

Accepted Answer

It moves $$3\ \mathrm{Na^+}$$ out and $$2\ \mathrm{K^+} in $$per ATP hydrolyzed

Question 16

During the repolarization phase, which channels are open?

Accepted Answer

Voltage-gated potassium channels

Question 17

A neuron is unable to return to its resting potential after an action potential. Which process is most likely impaired?

Accepted Answer

Function of the sodium-potassium pump

Question 18

Which of the following best describes the change in membrane potential during depolarization?

Accepted Answer

The membrane potential becomes less negative as sodium ions enter the cell

Question 19

If a neuron is exposed to a drug that prevents potassium ($$\mathrm{K^+}) $$channels from closing, what is the most likely effect?

Accepted Answer

The neuron will remain hyperpolarized for a longer period

Action Potentials in Neurons: Sequence, Ion Channel Dynamics, and Clinical Applications

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