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

The membrane potential would move closer to $$0\ \text{mV}.$$

Question 1

Which of the following best describes the function of the Na+/K+ pump in maintaining the resting membrane potential of a neuron?

Accepted Answer

It actively transports 3 Na+ out of the cell and 2 K+ into the cell, using ATP.

Question 2

A neuron at rest has a membrane potential of approximately $$-70\ 	ext{mV}. $$What causes this negative potential?

Accepted Answer

Higher concentration of K+ inside the cell and Na+ outside, combined with selective permeability to K+.

Question 3

Which equation is used to calculate the equilibrium potential for a particular ion, where the electrical and chemical gradients are balanced?

Accepted Answer

The Nernst equation: $$E_{	ext{ion}} = \frac{RT}{zF} \ln \left( \frac{[	ext{ion}]_{	ext{outside}}}{[	ext{ion}]_{	ext{inside}}} ight)$$

Question 4

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

Accepted Answer

The membrane potential would move closer to $$0\ 	ext{mV}.$$

Question 5

During the depolarization phase of an action potential, which ion's movement is primarily responsible for the change in membrane potential?

Accepted Answer

Influx of Na+ ions

Question 6

A cone snail injects venom that blocks neuromuscular pathways. Which step in neural signaling is most directly affected by this venom?

Accepted Answer

Transmission of signals across the synapse via neurotransmitter release

Question 7

If a neuron is exposed to a stimulus that opens voltage-gated K+ channels, what is the expected effect on the membrane potential?

Accepted Answer

Hyperpolarization, making the membrane more negative

Question 8

Which of the following best explains why graded potentials decay with distance?

Accepted Answer

Current is lost through the 'leaky' plasma membrane, causing voltage to decline with distance.

Question 9

What is the 'all-or-none' phenomenon of action potentials?

Accepted Answer

Action potentials only occur if the membrane potential reaches threshold, and are always the same size.

Question 10

Which phase of the action potential is characterized by the opening of voltage-gated K+ channels and the efflux of K+ ions?

Accepted Answer

Repolarization

Question 11

A neuron is exposed to two simultaneous depolarizing stimuli. What is the likely outcome?

Accepted Answer

The magnitude of the depolarizing current will increase, making it more likely to reach threshold.

Question 12

Which of the following is true about the absolute refractory period?

Accepted Answer

Voltage-gated channels are locked down and a second action potential cannot be initiated.

Question 13

What is the threshold voltage required to initiate an action potential in most neurons?

Accepted Answer

$$-50 to$$ $$-55\ 	ext{mV}$$

Question 14

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

Accepted Answer

They open or close in response to changes in membrane voltage, allowing rapid ion flow.

Question 15

If the Na+/K+ pump is inhibited, what would happen to the neuron’s ability to generate action potentials over time?

Accepted Answer

The neuron would lose its ion gradients, making it unable to reach threshold and fire action potentials.

Question 16

Which of the following ions has the highest concentration inside a resting neuron?

Accepted Answer

K+

Question 17

A patient is exposed to a toxin that selectively opens voltage-gated Na+ channels. What is the most likely effect on their neurons?

Accepted Answer

The neurons will depolarize, potentially leading to uncontrolled action potentials.

Question 18

Which of the following best explains why action potentials can be transmitted over long distances, unlike graded potentials?

Accepted Answer

Action potentials are regenerated at each segment of the axon by opening of voltage-gated channels.

Question 19

Which of the following is a real-world example of a graded potential leading to an action potential?

Accepted Answer

A neuron receiving neurotransmitter at its dendrite, depolarizing, and then firing an action potential if threshold is reached.

Neurons, Synapses, and Signaling: Membrane Potentials and Action Potentials

Study Guide - Practice Questions