Question 1

Which ion is primarily responsible for establishing the resting membrane potential in most neurons, and why?

Accepted Answer

Potassium, because the membrane is highly permeable to K+ at rest.

Question 2

What would happen to the resting membrane potential if the membrane became equally permeable to both Na+ and K+?

Accepted Answer

It would become more positive, moving toward the Na+ equilibrium potential.

Question 3

Which equation predicts the membrane potential by considering the combined contributions of all permeant ions and their permeabilities?

Accepted Answer

Goldman-Hodgkin-Katz (GHK) equation

Question 4

Given the GHK equation: $$V_m = 61 \log \frac{P_K[K^+]_{out} + P_{Na}[Na^+]_{out} + P_{Cl}[Cl^-]_{in}}{P_K[K^+]_{in} + P_{Na}[Na^+]_{in} + P_{Cl}[Cl^-]_{out}}$$, what would happen to $$V_m if$$ $$P_{Na}$$ increases significantly?

Accepted Answer

The membrane potential would become more positive.

Question 5

Which of the following best describes the effect of opening more chloride (Cl-) channels in a neuron at rest?

Accepted Answer

The membrane potential becomes more negative (hyperpolarization).

Question 6

A mutation causes a voltage-gated Na+ channel to remain open longer than normal. What is the most likely effect on neuronal signaling?

Accepted Answer

The neuron will depolarize more easily and may fire repetitively.

Question 7

Which type of ion channel is primarily responsible for the rapid depolarization phase of the action potential in neurons?

Accepted Answer

Voltage-gated Na+ channels

Question 8

According to Ohm’s law, what happens to the current ($$I) if $$the resistance ($$R) $$increases while the voltage ($$V) $$remains constant? $$I = \frac{V}{R}$$

Accepted Answer

Current decreases.

Question 9

Which of the following is NOT a typical effect of channelopathies?

Accepted Answer

Increased production of neurotransmitters

Question 10

If a neuron’s membrane potential changes from -70 mV to -90 mV, which term best describes this change?

Accepted Answer

Hyperpolarization

Question 11

Which of the following statements about leak channels is TRUE?

Accepted Answer

They are considered high conductance channels because they are almost always open.

Question 12

Which of the following would most likely cause a neuron to depolarize?

Accepted Answer

Opening more Na+ channels

Question 13

A patient has a mutation that increases the membrane resistance ($$R_m) of $$their neurons. According to Ohm’s law, what is the effect on current flow ($$I) if $$voltage ($$V) is $$unchanged? $$I = \frac{V}{R}$$

Accepted Answer

Current flow decreases.

Question 14

Which of the following best explains why the resting membrane potential is not exactly equal to the equilibrium potential for K+?

Accepted Answer

There is some permeability to Na+, which makes the potential slightly more positive.

Question 15

Which of the following is a property of voltage-gated ion channels?

Accepted Answer

They open in response to changes in membrane potential.

Question 16

Which of the following is a direct consequence of a mutation that prevents inactivation of a voltage-gated Na+ channel?

Accepted Answer

The neuron may remain depolarized for longer periods.

Question 17

Which of the following best describes the Nernst equation?

Accepted Answer

It calculates the equilibrium potential for a single ion.

Question 18

Which of the following is NOT a factor that influences the membrane potential of a neuron?

Accepted Answer

The temperature of the extracellular fluid

Question 19

A neuron is exposed to a drug that increases the permeability of the membrane to Ca2+. What is the most likely effect on the membrane potential?

Accepted Answer

The membrane potential will become more positive (depolarize).

Question 20

Which of the following best describes the conductance of an ion channel?

Accepted Answer

The ease with which ions flow through the channel

Membrane Potentials and Ion Channels in Neurons

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