Question 1

Which of the following best describes the resting membrane potential of a typical neuron?

Accepted Answer

It is approximately $$-70\ \mathrm{mV}$$, mainly due to potassium ion permeability.

Question 2

What is the primary function of the sodium-potassium pump ($$\mathrm{Na^+/K^+}$$ ATPase) in maintaining the resting membrane potential?

Accepted Answer

It pumps $$3\ \mathrm{Na^+}$$ out and $$2\ \mathrm{K^+} in$$, creating an electrochemical gradient.

Question 3

During depolarization of an action potential, which ion channels open and what is the result?

Accepted Answer

Sodium channels open, causing the membrane potential to become more positive.

Question 4

Which of the following equations can be used to estimate the equilibrium potential for potassium ions ($$E_K) $$across a membrane?

Accepted Answer

$$E_K = \frac{RT}{zF} \ln \left( \frac{[K^+]_{out}}{[K^+]_{in}} \right)$$

Question 5

A graded potential differs from an action potential in which of the following ways?

Accepted Answer

Graded potentials can summate and vary in amplitude.

Question 6

If the extracellular concentration of potassium increases, what effect would this have on the resting membrane potential?

Accepted Answer

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

Question 7

Which statement best explains why the inside of a neuron is negatively charged at rest?

Accepted Answer

Potassium ions leak out of the cell, leaving behind negatively charged proteins.

Question 8

Which of the following best describes the refractory period of an action potential?

Accepted Answer

It is the period during which a neuron cannot initiate another action potential.

Question 9

A neuron receives two simultaneous graded potentials: one depolarizing and one hyperpolarizing. What is the likely outcome?

Accepted Answer

The effects will summate, and the net change will depend on their relative strengths.

Question 10

Which of the following is true regarding the propagation of an action potential along an axon?

Accepted Answer

It is regenerated at each segment of the axon due to voltage-gated channels.

Question 11

What is the effect of opening ligand-gated sodium channels on the postsynaptic membrane?

Accepted Answer

It causes depolarization.

Question 12

Which of the following best describes the threshold potential in neurons?

Accepted Answer

It is the membrane potential at which voltage-gated sodium channels open.

Question 13

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

Accepted Answer

Action potentials are all-or-none, while graded potentials are variable in size.

Question 14

If a neuron is exposed to a drug that blocks voltage-gated potassium channels, what would be the most likely effect on the action potential?

Accepted Answer

Repolarization would be delayed, prolonging the action potential.

Question 15

Which of the following best explains the concept of 'electrochemical gradient' as it applies to neurons?

Accepted Answer

It is the combined effect of concentration gradient and electrical gradient on ion movement.

Question 16

Which of the following events occurs first during the generation of an action potential?

Accepted Answer

Opening of voltage-gated sodium channels.

Question 17

A patient has a mutation that causes their sodium channels to inactivate more slowly than normal. What effect would this have on their action potentials?

Accepted Answer

Action potentials would be prolonged and reach a higher peak.

Question 18

Which of the following best describes the effect of myelination on action potential conduction?

Accepted Answer

It allows action potentials to jump between nodes of Ranvier, increasing speed.

Question 19

Which of the following is true regarding the effect of graded potentials on the postsynaptic neuron?

Accepted Answer

They can be depolarizing or hyperpolarizing, affecting the likelihood of action potential generation.

Question 20

Which of the following best explains why action potentials do not summate?

Accepted Answer

Because of the refractory period, a second action potential cannot be initiated until the first is complete.

Membrane Potentials and Neural Signaling: Resting, Graded, and Action Potentials

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