Q: Which of the following equations correctly represents the action of the sodium-potassium pump per ATP molecule hydrolyzed?

$$3\ \mathrm{Na^+}_{\text{in}} \rightarrow 3\ \mathrm{Na^+}_{\text{out}}$$ and $$2\ \mathrm{K^+}_{\text{out}} \rightarrow 2\ \mathrm{K^+}_{\text{in}}$$

Question 1

Which of the following best explains why neurons are considered highly excitable compared to most other cells?

Accepted Answer

They possess a resting membrane potential and specialized ion channels that allow rapid changes in membrane voltage.

Question 2

A patient is given a drug that blocks all voltage-gated sodium ($$\mathrm{Na^+}) $$channels in neurons. What is the most likely effect on action potential generation?

Accepted Answer

Action potentials will be unable to initiate because $$\mathrm{Na^+}$$ influx is required for depolarization.

Question 3

Which of the following statements about the sodium-potassium pump ($$\mathrm{Na^+/K^+}$$ ATPase) is correct?

Accepted Answer

It moves three $$\mathrm{Na^+}$$ ions out and two $$\mathrm{K^+}$$ ions in per ATP hydrolyzed.

Question 4

During the resting membrane potential, which ion has the greatest influence on the membrane voltage, and why?

Accepted Answer

$$\mathrm{K^+}$$, because the membrane is 25 times more permeable to potassium than sodium due to more leakage channels.

Question 5

A neuron is exposed to a toxin that increases the permeability of the membrane to $$\mathrm{Na^+}. $$What is the most likely immediate effect on the membrane potential?

Accepted Answer

The membrane will depolarize.

Question 6

Which of the following best describes the difference between graded potentials and action potentials?

Accepted Answer

Graded potentials are short-lived and localized, while action potentials are long-distance signals that do not decrease in strength.

Question 7

Which of the following equations correctly represents the action of the sodium-potassium pump per ATP molecule hydrolyzed?

Accepted Answer

$$3\ \mathrm{Na^+}_{	ext{in}} ightarrow 3\ \mathrm{Na^+}_{	ext{out}}$$ and $$2\ \mathrm{K^+}_{	ext{out}} ightarrow 2\ \mathrm{K^+}_{	ext{in}}$$

Question 8

A neuron receives a stimulus that opens chemically gated ion channels. Which type of potential is most likely generated?

Accepted Answer

Graded potential

Question 9

Which of the following best explains why action potentials only propagate in one direction along an axon?

Accepted Answer

Voltage-gated $$\mathrm{Na^+}$$ channels behind the action potential are inactivated, creating a refractory period.

Question 10

A patient has a demyelinating disease affecting their peripheral nerves. Which of the following changes in nerve conduction would you expect?

Accepted Answer

Decreased speed of action potential propagation due to loss of saltatory conduction.

Question 11

Which of the following is true regarding the absolute refractory period during an action potential?

Accepted Answer

No stimulus, regardless of strength, can initiate another action potential during this period.

Question 12

Which of the following best describes saltatory conduction?

Accepted Answer

Action potentials jump from one node of Ranvier to the next, increasing conduction velocity.

Question 13

Which group of nerve fibers would transmit a sharp pain sensation from the skin to the brain most rapidly?

Accepted Answer

Group A fibers

Question 14

If the extracellular concentration of $$\mathrm{K^+}$$ increases significantly, what is the most likely effect on the resting membrane potential?

Accepted Answer

The resting membrane potential will become less negative (depolarize).

Question 15

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

Accepted Answer

Once threshold is reached, an action potential of fixed size is generated; if threshold is not reached, no action potential occurs.

Question 16

A neuron is exposed to a drug that blocks all leakage (nongated) $$\mathrm{K^+}$$ channels. What is the most likely effect on the resting membrane potential?

Accepted Answer

The resting membrane potential will become less negative (depolarize).

Question 17

Which of the following is a key difference between voltage-gated sodium ($$\mathrm{Na^+}) $$and potassium ($$\mathrm{K^+}) $$channels during an action potential?

Accepted Answer

Sodium channels have both activation and inactivation gates, while potassium channels have only an activation gate.

Question 18

A graded potential in a postsynaptic neuron is most likely to be triggered by which of the following?

Accepted Answer

Binding of a neurotransmitter to chemically gated ion channels on the dendrite.

Question 19

Which of the following factors would increase the conduction velocity of an action potential along an axon?

Accepted Answer

Increasing the degree of myelination.

Neurophysiology: Membrane Potentials and Action Potentials

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