Question 1

Which of the following best describes the difference between graded potentials and action potentials in neurons?

Accepted Answer

Graded potentials vary in strength and lose amplitude over short distances, while action potentials are uniform in strength and travel long distances without losing amplitude.

Question 2

A neuron receives multiple excitatory and inhibitory inputs. Which scenario is most likely to trigger an action potential at the axon hillock?

Accepted Answer

The sum of excitatory postsynaptic potentials (EPSPs) brings the membrane potential to $-55\ \mathrm{mV}$.

Question 3

During the rising phase of an action potential, which ion moves and in which direction?

Accepted Answer

Na+ moves into the cell, causing depolarization.

Question 4

What is the primary reason graded potentials lose strength as they travel through the neuron?

Accepted Answer

Current leak through open channels and cytoplasmic resistance.

Question 5

Which phase of the action potential is associated with the opening of voltage-gated K+ channels?

Accepted Answer

Repolarization phase

Question 6

A patient’s neuron membrane potential is measured at $-70\ \mathrm{mV}$. What does this value represent?

Accepted Answer

The resting membrane potential.

Question 7

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

Accepted Answer

The absolute refractory period prevents re-initiation of action potentials in recently depolarized regions.

Question 8

If a neuron is in the relative refractory period, what is required to initiate another action potential?

Accepted Answer

A stimulus stronger than normal to overcome the more negative membrane potential.

Question 9

Which equation best represents the Nernst equation for calculating the equilibrium potential of an ion?

Accepted Answer

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

Question 10

A neuron receives a mechanical stimulus that opens ion channels. What type of potential is most likely generated?

Accepted Answer

A graded potential at the site of stimulation.

Question 11

Which of the following is TRUE regarding the role of ATPase in neurons?

Accepted Answer

It restores ion gradients by pumping Na+ out and K+ in after action potentials.

Question 12

Which of the following best describes the all-or-none property of action potentials?

Accepted Answer

Action potentials are only generated if the membrane potential reaches threshold, and their amplitude does not change with stimulus strength.

Question 13

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

Accepted Answer

The neuron will remain depolarized and unable to repolarize, leading to continuous firing.

Question 14

Which of the following is a consequence of the refractory period in neurons?

Accepted Answer

It limits the frequency at which action potentials can be generated.

Question 15

If the membrane potential at the axon hillock is $-60\ \mathrm{mV}$, what is the most likely outcome?

Accepted Answer

No action potential will be generated unless the threshold of $-55\ \mathrm{mV}$ is reached.

Question 16

Which of the following best describes the movement of ions during the after-hyperpolarization phase of an action potential?

Accepted Answer

Voltage-gated K+ channels remain open, allowing excess K+ to leave the cell.

Question 17

A neuron is exposed to a drug that increases cytoplasmic resistance. What effect will this have on graded potentials?

Accepted Answer

Graded potentials will lose strength more rapidly as they travel.

Question 18

Which of the following is NOT a function of the refractory period?

Accepted Answer

Increasing the amplitude of action potentials.

Question 19

A sensory neuron receives a thermal stimulus that causes a depolarizing graded potential. What is the next event if the depolarization is large enough?

Accepted Answer

An action potential is triggered at the axon hillock.

Electrical Signals in Neurons: Graded and Action Potentials N4

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