The membrane potential is at $$-70\ \text{mV}$$, with most sodium and potassium channels closed.

Sodium ($$\text{Na}^+) $$moves in through sodium channels.

$$E = \frac{RT}{zF} \ln \left( \frac{[\text{ion}]_{\text{outside}}}{[\text{ion}]_{\text{inside}}} \right)$$

Question 1

Which of the following best describes the resting potential of a neuron, as shown in the central graph of the image?

Accepted Answer

The membrane potential is at $$-70\ 	ext{mV}$$, with most sodium and potassium channels closed.

Question 2

During the depolarization phase of the action potential (bottom left panel), which ion moves into the neuron and through which channel?

Accepted Answer

Sodium ($$	ext{Na}^+) $$moves in through sodium channels.

Question 3

What triggers the opening of voltage-gated sodium channels during the action potential?

Accepted Answer

A depolarization of the membrane to the threshold value.

Question 4

Which phase of the action potential is characterized by the opening of voltage-gated potassium channels and the closing of sodium channels?

Accepted Answer

Repolarization phase

Question 5

What is the primary function of the inactivation loop in the sodium channel, as shown in the lower left panel?

Accepted Answer

To block the sodium channel after depolarization, preventing further sodium entry.

Question 6

If the membrane potential does not reach the threshold value, what happens to the action potential?

Accepted Answer

No action potential is generated; the response is all-or-none.

Question 7

During the falling phase of the action potential (top right panel), which ion is primarily moving out of the neuron?

Accepted Answer

Potassium ($$	ext{K}^+)$$

Question 8

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

Accepted Answer

$$E = \frac{RT}{zF} \ln \left( \frac{[	ext{ion}]_{	ext{outside}}}{[	ext{ion}]_{	ext{inside}}} ight)$$

Question 9

Which of the following best explains why ions cannot freely diffuse across the plasma membrane?

Accepted Answer

Ions are charged and require specific protein channels to cross the membrane.

Question 10

What is the effect of myelin sheaths on the conduction of action potentials?

Accepted Answer

They speed up transmission by allowing action potentials to jump between nodes of Ranvier (saltatory conduction).

Question 11

If a neuron is affected by multiple sclerosis, which part of the action potential transmission is most likely disrupted?

Accepted Answer

The rapid conduction of action potentials along myelinated axons.

Question 12

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

Accepted Answer

Once threshold is reached, a full action potential is generated; if not, no action potential occurs.

Question 13

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

Accepted Answer

The sodium channels are inactivated and cannot reopen immediately.

Question 14

Which of the following is a correct sequence of events during an action potential?

Accepted Answer

Resting potential → Depolarization → Repolarization → Hyperpolarization → Resting potential

Question 15

Which of the following would most likely occur if the sodium-potassium pump stopped functioning?

Accepted Answer

The concentration gradients of $$	ext{Na}^+$$ and $$	ext{K}^+$$ would dissipate, and the neuron could not generate action potentials.

Study Guide: Neurons, Synapses, Signaling, and Nervous/Sensory Systems

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