Question 1

Which of the following best explains why the resting membrane potential of a neuron is typically negative?

Accepted Answer

Potassium ions ($K^+$) leak out of the cell through channels more readily than sodium ions ($Na^+$) enter, and large negatively charged proteins remain inside.

Question 2

What is the primary function of voltage-gated sodium channels during the initiation of an action potential?

Accepted Answer

To allow $Na^+$ ions to enter the cell, causing depolarization.

Question 3

During the repolarization phase of an action potential, which ion movement is primarily responsible for returning the membrane potential toward its resting value?

Accepted Answer

$K^+$ ions leaving the cell.

Question 4

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

Accepted Answer

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

Question 5

A neuron is exposed to a drug that blocks all voltage-gated potassium channels. What is the most likely effect on the action potential?

Accepted Answer

Repolarization will be delayed, causing a prolonged action potential.

Question 6

Which of the following best describes saltatory conduction in myelinated axons?

Accepted Answer

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

Question 7

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

Accepted Answer

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

Question 8

Which of the following is TRUE regarding the refractory period of a neuron?

Accepted Answer

It prevents the backward propagation of action potentials.

Question 9

A patient is given a drug that increases the permeability of the neuronal membrane to $Na^+$ at rest. What is the most likely effect?

Accepted Answer

The neuron will depolarize and become more likely to fire an action potential.

Question 10

Which of the following best describes the role of neurotransmitters in synaptic transmission?

Accepted Answer

They are released into the synaptic cleft and bind to receptors on the postsynaptic cell.

Question 11

Which of the following statements about ion channels is correct?

Accepted Answer

Ion channels can be selective for particular ions and may be gated or leak channels.

Question 12

During the absolute refractory period, why can't a neuron fire another action potential?

Accepted Answer

The sodium channels are inactivated and cannot reopen immediately.

Question 13

Which of the following would most likely increase the frequency of action potentials in a neuron?

Accepted Answer

Increasing the amplitude of the stimulus above threshold.

Question 14

A mutation causes voltage-gated sodium channels to remain open longer than normal. What effect would this have on the action potential?

Accepted Answer

The action potential would have a higher peak and longer duration.

Question 15

Which of the following best explains why myelinated axons conduct action potentials faster than unmyelinated axons?

Accepted Answer

Myelin allows action potentials to jump between nodes of Ranvier, reducing the number of times the membrane must depolarize.

Question 16

Which of the following scenarios would most likely result in a neuron failing to reach threshold and fire an action potential?

Accepted Answer

The stimulus amplitude is below the threshold value.

Question 17

Which of the following is a direct result of the opening of voltage-gated potassium channels during an action potential?

Accepted Answer

Repolarization of the membrane.

Question 18

If a neuron’s dendrites receive simultaneous excitatory and inhibitory synaptic inputs, what determines whether an action potential will be generated?

Accepted Answer

The sum of all postsynaptic potentials at the axon hillock.

Question 19

Which of the following best describes the effect of synaptic transmission on dendritic membrane potential?

Accepted Answer

It can cause either depolarization or hyperpolarization, depending on the neurotransmitter and receptor.

Question 20

Which of the following is a characteristic of gated ion channels, but NOT leak channels?

Accepted Answer

They open only in response to specific stimuli, such as changes in membrane potential.

Nervous System: Structure, Function, and Action Potentials

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