Question 1

Which of the following best describes the function of voltage-gated ion channels in the generation of an action potential?

Accepted Answer

They open in response to changes in the electrical properties of the membrane, allowing specific ions to cross.

Question 2

A cell membrane is said to be 'electrically excitable' because:

Accepted Answer

It can generate and propagate action potentials due to the presence of voltage-gated ion channels.

Question 3

Which of the following equations best represents the Nernst equation for calculating the equilibrium potential ($E_{ion}$) for a particular ion across a membrane?

Accepted Answer

$E_{ion} = \frac{RT}{zF} \ln \left( \frac{[ion]_{outside}}{[ion]_{inside}} \right)$

Question 4

A ligand-gated channel will open when:

Accepted Answer

A specific molecule, such as a neurotransmitter, binds to the channel protein.

Question 5

Which of the following best explains why the inside of a neuron is negatively charged relative to the outside at rest?

Accepted Answer

The cell membrane is more permeable to potassium ions, which diffuse out, leaving behind negatively charged proteins.

Question 6

A mechanically gated channel is most likely to be found in which of the following scenarios?

Accepted Answer

A sensory neuron in the skin responding to pressure.

Question 7

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

Accepted Answer

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

Question 8

Which of the following statements about leak channels is correct?

Accepted Answer

Leak channels are randomly gated, allowing ions to move across the membrane at all times.

Question 9

A researcher uses a voltmeter to measure the membrane potential of a neuron. The reference electrode is placed outside the cell, and the recording microelectrode is inserted inside the cell. The voltmeter reads $-70$ mV. What does this value represent?

Accepted Answer

The inside of the cell is $70$ mV more negative than the outside.

Question 10

Which of the following best describes the role of the sodium-potassium pump ($Na^+/K^+$ ATPase) in maintaining the resting membrane potential?

Accepted Answer

It pumps $3$ sodium ions out of the cell and $2$ potassium ions into the cell, using ATP.

Question 11

A mutation causes a ligand-gated sodium channel to remain open even in the absence of its ligand. What is the most likely effect on the cell's membrane potential?

Accepted Answer

The membrane potential would become less negative (depolarize).

Question 12

Which of the following is NOT a characteristic of voltage-gated channels?

Accepted Answer

They open in response to the binding of a specific chemical messenger.

Question 13

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

Accepted Answer

It would move toward $0$ mV, becoming less negative.

Question 14

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

Accepted Answer

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

Question 15

A toxin blocks all voltage-gated potassium channels in a neuron. What is the most likely effect on the action potential?

Accepted Answer

The neuron would be unable to repolarize efficiently, prolonging the action potential.

Question 16

Which of the following best describes the function of a ligand-gated channel at a synapse?

Accepted Answer

It opens when a neurotransmitter binds, allowing ions to flow and generating a postsynaptic potential.

Question 17

Which of the following is a direct result of the selective permeability of the cell membrane to different ions?

Accepted Answer

A difference in charge (membrane potential) is established across the membrane.

The Action Potential and Membrane Physiology

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