Q: Which of the following equations correctly represents the action of the Na$$^+/K$^+$$ ATPase pump?

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

Question 1

Which of the following best explains why the resting membrane potential of a neuron is typically around $$-70\ \mathrm{mV}$$?

Accepted Answer

The membrane is more permeable to K$$^+$$ than to Na$$^+$$, allowing more K$$^+ to $$diffuse out than Na$$^+ to $$diffuse in.

Question 2

A neuron is exposed to a chemical that blocks voltage-gated Na$$^+$$ channels. What would be the most immediate effect on the neuron's ability to generate an action potential?

Accepted Answer

The neuron would be unable to depolarize and thus could not generate an action potential.

Question 3

During the repolarization phase of an action potential, which of the following events occurs?

Accepted Answer

Voltage-gated K$$^+$$ channels open and K$$^+$$ exits the cell.

Question 4

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

Accepted Answer

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

Question 5

A patient has a genetic mutation that causes their neurons to lack myelin sheaths. Which of the following would most likely be observed?

Accepted Answer

Action potentials would propagate more slowly due to the lack of saltatory conduction.

Question 6

Which of the following equations correctly represents the action of the Na$$^+/K$^+$$ ATPase pump?

Accepted Answer

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

Question 7

Which of the following scenarios would most likely result in hyperpolarization of a neuron's membrane?

Accepted Answer

Opening of chemically gated K$$^+$$ channels.

Question 8

A graded potential is most likely to occur in which of the following situations?

Accepted Answer

A neurotransmitter binds to a chemically gated ion channel on a dendrite.

Question 9

Which of the following best explains why action potentials do not decay as they travel along an axon, while graded potentials do?

Accepted Answer

Action potentials are regenerated at each segment of the axon by voltage-gated ion channels.

Question 10

During the absolute refractory period, which of the following is true?

Accepted Answer

No stimulus, no matter how strong, can generate another action potential.

Question 11

Which of the following best describes saltatory conduction?

Accepted Answer

Action potentials jump from one node of Ranvier to the next in myelinated axons.

Question 12

A neuron receives a stimulus that depolarizes the membrane from $$-70\ \mathrm{mV} to$$ $$-60\ \mathrm{mV}. If $$the threshold for this neuron is $$-55\ \mathrm{mV}$$, what will happen?

Accepted Answer

A graded potential will occur, but no action potential will be generated.

Question 13

Which of the following is a direct result of the opening of voltage-gated Na$$^+$$ channels during an action potential?

Accepted Answer

The membrane potential rapidly rises toward $$+30\ \mathrm{mV}.$$

Question 14

Which of the following best explains why Group A nerve fibers conduct impulses faster than Group C fibers?

Accepted Answer

Group A fibers have a larger diameter and are myelinated, reducing resistance and increasing conduction speed.

Question 15

If the extracellular concentration of K$$^+$$ increases significantly, what effect would this have on the resting membrane potential?

Accepted Answer

The resting membrane potential would become less negative (depolarized).

Question 16

Which of the following is true regarding the frequency of action potentials and stimulus intensity?

Accepted Answer

A stronger stimulus increases the frequency of action potentials generated.

Question 17

A neuron is exposed to a toxin that prevents the closing of voltage-gated K$$^+$$ channels. What would be the most likely effect on the action potential?

Accepted Answer

The neuron would experience prolonged hyperpolarization after each action potential.

Question 18

Which of the following best describes the role of the Na$$^+/K$^+$$ ATPase in maintaining the resting membrane potential?

Accepted Answer

It actively transports 3 Na$$^+$$ out of the cell and 2 K$$^+$$ into the cell, maintaining concentration gradients.

Membrane Potentials and Action Potentials: Fundamentals of the Nervous System

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