Question 1

Which phase of the action potential is characterized by a rapid influx of sodium ions ($$\mathrm{Na^+}) $$into the neuron, causing the membrane potential to become more positive?

Accepted Answer

Depolarization

Question 2

During which phase does the membrane potential return toward the resting value after reaching its peak, primarily due to the efflux of potassium ions ($$\mathrm{K^+}$$)?

Accepted Answer

Repolarization

Question 3

What is the typical threshold value (in mV) that must be reached for an action potential to be initiated in a neuron?

Accepted Answer

$$-55\ \mathrm{mV}$$

Question 4

Which of the following best describes a graded potential?

Accepted Answer

A small, localized change in membrane potential that can summate

Question 5

If a neuron is exposed to a toxin that blocks voltage-gated sodium channels, which phase of the action potential would be directly prevented?

Accepted Answer

Depolarization

Question 6

Which of the following best explains why action potentials are described as 'all-or-none'?

Accepted Answer

They only occur if the threshold is reached, otherwise not at all

Question 7

A patient presents with symptoms of muscle weakness. Laboratory tests reveal that their neurons are unable to repolarize efficiently. Which ion channel is most likely malfunctioning?

Accepted Answer

Voltage-gated potassium channels

Question 8

Which part of the neuron is primarily responsible for initiating the action potential, as shown in the diagrams?

Accepted Answer

Axon hillock

Question 9

If the resting membrane potential is $$-70\ \mathrm{mV}$$ and the threshold is $$-55\ \mathrm{mV}$$, what is the minimum change in membrane potential required to trigger an action potential?

Accepted Answer

$$15\ \mathrm{mV}$$

Question 10

Which of the following scenarios would most likely result in hyperpolarization of a neuron?

Accepted Answer

Opening of ligand-gated chloride channels

Question 11

A graded potential fails to reach threshold at the axon hillock. What is the most likely outcome?

Accepted Answer

No action potential occurs

Question 12

Which of the following best describes the sequence of events during an action potential?

Accepted Answer

Resting membrane potential → Depolarization → Repolarization → Hyperpolarization

Question 13

Which of the following is a key difference between graded potentials and action potentials?

Accepted Answer

Graded potentials can summate, while action potentials cannot

Question 14

If a neuron is exposed to a drug that increases the permeability of the membrane to potassium ions ($$\mathrm{K^+}) at $$rest, what would happen to the resting membrane potential?

Accepted Answer

It would become more negative

Question 15

Which of the following best explains why the action potential does not travel backward along the axon?

Accepted Answer

Voltage-gated sodium channels are inactivated during the refractory period

Sketch #3

Study Guide - Practice Questions

Study Guide - Flashcards