Question 1

Which of the following best describes the resting membrane potential (RMP) of a typical neuron?

Accepted Answer

It is the voltage difference across the membrane when the neuron is not actively sending signals, typically around $$-65 mV.$$

Question 2

What is the primary factor that determines the resting membrane potential (RMP) in neurons?

Accepted Answer

The permeability of the membrane to potassium ions ($$K^+)$$

Question 3

If a neuron’s membrane potential is at $$-120 mV$$, which direction will $$K^+$$ ions flow through open leak channels, and what effect will this have on the membrane potential?

Accepted Answer

$$K^+$$ will flow out of the neuron, causing depolarization.

Question 4

Which equation is used to calculate the equilibrium potential ($$E_{ion}) $$for a specific ion across a membrane?

Accepted Answer

$$E_{ion} = 2.303 \frac{RT}{zF} \log \frac{[ion]_{out}}{[ion]_{in}}$$

Question 5

A positive ion influx into a neuron will result in which of the following?

Accepted Answer

Depolarization

Question 6

Which of the following statements about the Na$$^+/K$^+$$ ATPase pump is correct?

Accepted Answer

It moves 3 Na$$^+$$ ions out of the cell and 2 K$$^+$$ ions into the cell per cycle.

Question 7

Which of the following best explains why the equilibrium potential for potassium ($$E_K) is $$close to the resting membrane potential?

Accepted Answer

The membrane is most permeable to $$K^+ at $$rest due to open K$$^+$$ leak channels.

Question 8

If the extracellular concentration of $$K^+$$ increases from 5 mM to 10 mM, what will happen to the equilibrium potential for $$K^+$$ ($$E_K$$)?

Accepted Answer

$$E_K$$ will become less negative.

Question 9

Which of the following is TRUE regarding the driving force for ion movement across the membrane?

Accepted Answer

It is calculated as $$V_m - E_{ion}$$, where $$V_m is $$the membrane potential and $$E_{ion} is $$the equilibrium potential for the ion.

Question 10

A neuron is at rest with a membrane potential of $$-65 mV. If $$the membrane suddenly becomes highly permeable to Na$$^+$$, what will happen to the membrane potential?

Accepted Answer

It will move towards the equilibrium potential of Na$$^+$$ ($$E_{Na}$$), becoming more positive.

Question 11

Which of the following statements about ion channels is correct?

Accepted Answer

Leak channels are always open and not gated by voltage or ligands.

Question 12

Which of the following would cause hyperpolarization of a neuron?

Accepted Answer

Negative ion influx

Question 13

If the membrane is impermeable to an ion, what effect does the driving force have on the movement of that ion?

Accepted Answer

The ion will not move regardless of the driving force.

Question 14

Which of the following best describes the effect of the Na$$^+/K$^+$$ ATPase pump on the concentration gradients of Na$$^+$$ and K$$^+$$?

Accepted Answer

It maintains high extracellular Na$$^+$$ and high intracellular K$$^+.$$

Question 15

Which of the following ions has the highest permeability at rest in a typical neuron?

Accepted Answer

K$$^+$$

Question 16

A mutation causes the K$$^+$$ leak channels in a neuron to close. What is the most likely effect on the resting membrane potential?

Accepted Answer

The RMP will become more positive, moving closer to $$E_{Na}.$$

Question 17

Which of the following is TRUE about the Nernst equation at body temperature (37°C) for potassium?

Accepted Answer

$$E_K = 61.54 	ext{ mV} \log \frac{[K^+]_{out}}{[K^+]_{in}}$$

Question 18

Which of the following best explains why a small flux of ions can produce large changes in membrane potential?

Accepted Answer

The membrane potential is determined by the ratio of extracellular to intracellular ion concentrations, not the absolute numbers.

Question 19

Which of the following would most likely result from an increase in membrane permeability to Cl$$^- at $$rest?

Accepted Answer

The membrane potential would become more negative, moving towards $$E_{Cl}.$$

Resting Membrane Potential and Ion Flux in Neurons

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