Question 1

Which of the following best describes the function of the sodium-potassium pump in maintaining the resting membrane potential of a neuron?

Accepted Answer

It moves 3 Na$$^+$$ ions out of the cell and 2 K$$^+$$ ions into the cell, using ATP.

Question 2

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

Accepted Answer

Voltage-gated Na$$^+$$ channels open, allowing Na$$^+ to $$enter the cell.

Question 3

What is the primary reason for the negative resting membrane potential in neurons?

Accepted Answer

The membrane is more permeable to K$$^+$$ than to Na$$^+$$, allowing more K$$^+ to $$leave the cell.

Question 4

Which of the following best explains why action potentials travel in only one direction along an axon?

Accepted Answer

The inactivation of voltage-gated Na$$^+$$ channels prevents immediate reactivation behind the action potential.

Question 5

A neuron is placed in a solution containing 0.15 M NaCl on one side of a K$$^+-$$permeable membrane and 0.15 M KCl on the other. What will happen to the K$$^+$$ ions?

Accepted Answer

K$$^+$$ ions will move down their concentration gradient until an electrical equilibrium is reached.

Question 6

Which of the following correctly matches the state of the voltage-gated Na$$^+$$ channel with its function during the action potential?

Accepted Answer

Inactivated state: prevents further Na$$^+$$ entry during the refractory period.

Question 7

What is the effect of myelination on the conduction velocity of action potentials along an axon?

Accepted Answer

It increases conduction velocity by allowing action potentials to jump between nodes of Ranvier (saltatory conduction).

Question 8

Which of the following best describes the process of neurotransmitter release at a synapse?

Accepted Answer

Synaptic vesicles fuse with the presynaptic membrane and release neurotransmitter into the synaptic cleft by exocytosis.

Question 9

If the extracellular concentration of K$$^+$$ increases significantly, what is the most likely effect on the resting membrane potential?

Accepted Answer

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

Question 10

Which equation can be used to calculate the equilibrium potential for a particular ion across a membrane?

Accepted Answer

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

Question 11

A patient is given a drug that blocks voltage-gated K$$^+$$ channels. What is the most likely effect on the action potential?

Accepted Answer

Repolarization will be delayed, prolonging the action potential.

Question 12

Which of the following events occurs first during synaptic transmission at a chemical synapse?

Accepted Answer

An action potential arrives at the presynaptic terminal.

Question 13

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

Accepted Answer

There are more negatively charged proteins and ions inside the cell, and K$$^+$$ leaks out more readily than Na$$^+$$ enters.

Question 14

During the refractory period of an action potential, why can't a second action potential be generated?

Accepted Answer

Voltage-gated Na$$^+$$ channels are inactivated and cannot reopen immediately.

Question 15

Which of the following is a direct consequence of opening ligand-gated Na$$^+$$ channels at the postsynaptic membrane?

Accepted Answer

The postsynaptic cell depolarizes, possibly reaching threshold for an action potential.

Question 16

A neuron is exposed to a toxin that prevents the closing of voltage-gated Na$$^+$$ channels. What is the most likely effect?

Accepted Answer

The neuron will remain depolarized and be unable to repolarize properly.

Question 17

Which of the following best describes saltatory conduction?

Accepted Answer

Action potentials jump from one node of Ranvier to the next, increasing conduction speed.

Question 18

If a neuron is at rest and the membrane suddenly becomes permeable to Na$$^+$$, what will happen to the membrane potential?

Accepted Answer

The membrane potential will become more positive (depolarize).

Question 19

Which of the following is a key difference between voltage-gated Na$$^+$$ and K$$^+$$ channels?

Accepted Answer

Na$$^+$$ channels have three states (closed, open, inactivated), while K$$^+$$ channels have two states (open, closed).

Membrane Potential and Action Potential in Neurons

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