Question 1

Which of the following best describes the resting membrane potential ($$V_{rest}) of a $$typical neuron?

Accepted Answer

It is the voltage across the plasma membrane when the neuron is at rest, typically around $$-70 mV.$$

Question 2

What is the primary function of the Na$$^+/K$^+$$ pump in maintaining the resting membrane potential?

Accepted Answer

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

Question 3

According to Ohm’s law, which equation correctly relates membrane potential ($$E$$), current ($$I$$), and resistance ($$R) in a $$neuron?

Accepted Answer

$$I = E / R$$

Question 4

If a neuron’s membrane suddenly became equally permeable to both Na$$^+$$ and K$$^+$$, what would happen to the resting membrane potential?

Accepted Answer

It would become less negative, moving closer to 0 mV.

Question 5

Which equation is used to calculate the equilibrium potential for a specific ion, and what does it depend on?

Accepted Answer

The Nernst equation; depends on the ion’s charge and concentration gradient.

Question 6

Given the GHK equation for membrane potential:

$$Vm = 61 \log \frac{P_{Na}[Na^+]_o + P_{K}[K^+]_o}{P_{Na}[Na^+]_i + P_{K}[K^+]_i}$$

What would happen to $$V_m if$$ $$P_{Na}$$ increased significantly while $$P_{K}$$ remained constant?

Accepted Answer

$$V_m$$ would become more positive, approaching the Na$$^+$$ equilibrium potential.

Question 7

Which of the following best explains why the resting membrane potential is closer to the K$$^+$$ equilibrium potential than to the Na$$^+$$ equilibrium potential?

Accepted Answer

The membrane is much more permeable to K$$^+$$ than to Na$$^+.$$

Question 8

A cell is permeable only to K$$^+. If $$the concentration of K$$^+ is $$higher inside than outside, what will happen to the membrane potential as K$$^+$$ channels open?

Accepted Answer

The inside of the cell will become more negative.

Question 9

Which of the following is true regarding the equilibrium potential for Na$$^+$$ ($$E_{Na}) in $$neurons?

Accepted Answer

$$E_{Na} is $$approximately $$+60 mV.$$

Question 10

Which of the following best describes the effect of the Na$$^+/K$^+$$ pump on the resting membrane potential?

Accepted Answer

It maintains the Na$$^+$$ and K$$^+$$ gradients and contributes a small net positive charge outside the cell.

Question 11

If the membrane potential ($$V_m) is$$ $$-70 mV$$, the equilibrium potential for K$$^+$$ ($$E_K) is$$ $$-94 mV$$, and the equilibrium potential for Na$$^+$$ ($$E_{Na}) is$$ $$+60 mV$$, what is the direction of the electrochemical force on Na$$^+$$?

Accepted Answer

Na$$^+$$ will move into the cell.

Question 12

Which of the following equations describes the current for a specific ion ($$I_{ion}) $$across the membrane?

Accepted Answer

$$I_{ion} = g_{ion} (V_m - E_{ion})$$

Question 13

A neuron is at rest. If both Na$$^+$$ and K$$^+$$ channels suddenly open, which ion will move more rapidly and why?

Accepted Answer

Na$$^+$$, because its electrochemical force is much greater due to a larger difference between $$V_m$$ and $$E_{Na}.$$

Question 14

Which of the following best defines an equilibrium potential?

Accepted Answer

The membrane potential that counters the chemical forces acting to move an ion across the membrane.

Question 15

Which of the following is a graded potential?

Accepted Answer

A relatively small change in membrane potential produced by a specific type of stimulus.

Question 16

If the permeability of the membrane to K$$^+$$ increases while all other factors remain constant, what will happen to the membrane potential?

Accepted Answer

It will move closer to the K$$^+$$ equilibrium potential.

Establishment of the Resting Membrane Potential in Neurons

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