Voltage-gated Na\textsuperscript{+} channels open

It pumps 3 Na\textsuperscript{+} ions out and 2 K\textsuperscript{+} ions in, maintaining ion gradients.

Question 1

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

Accepted Answer

It is primarily due to the membrane's high permeability to K	extsuperscript{+} ions and low permeability to Na	extsuperscript{+} ions.

Question 2

What is the typical value of the resting membrane potential ($$V_{m,	ext{rest}}) in $$neurons?

Accepted Answer

$$-70\ 	ext{mV}$$

Question 3

Which type of ion channel is responsible for generating graded (local) potentials in neurons?

Accepted Answer

Ligand-gated (chemically-gated) and mechanically-gated channels

Question 4

During an action potential, which event occurs first after the threshold is reached?

Accepted Answer

Voltage-gated Na	extsuperscript{+} channels open

Question 5

What is the main function of the Na	extsuperscript{+}/K	extsuperscript{+} ATPase pump in maintaining the resting membrane potential?

Accepted Answer

It pumps 3 Na	extsuperscript{+} ions out and 2 K	extsuperscript{+} ions in, maintaining ion gradients.

Question 6

Which statement best explains why action potentials are 'all-or-none' events?

Accepted Answer

Action potentials only occur if the membrane potential reaches threshold; otherwise, no action potential is generated.

Question 7

If a neuron is exposed to a drug that blocks voltage-gated Na	extsuperscript{+} channels, what would be the most likely effect?

Accepted Answer

The neuron would be unable to generate action potentials.

Question 8

Which of the following best describes the process of saltatory conduction?

Accepted Answer

Action potentials jump from one node of Ranvier to the next, increasing conduction speed.

Question 9

What would happen to action potential conduction in a myelinated axon if the myelin is damaged?

Accepted Answer

Conduction would slow down or stop.

Question 10

Which of the following is true about graded potentials?

Accepted Answer

They decrease in strength as they spread from the point of origin.

Question 11

What is the effect of opening more K	extsuperscript{+} leak channels in the neuronal membrane?

Accepted Answer

The membrane potential becomes more negative (hyperpolarizes).

Question 12

Which of the following best explains why action potentials do not travel backward along the axon?

Accepted Answer

The refractory period prevents reactivation of recently depolarized regions.

Question 13

A neuron receives two subthreshold graded potentials at the same time at different locations. What is the most likely outcome?

Accepted Answer

The graded potentials may sum spatially and reach threshold, triggering an action potential.

Question 14

Which equation best represents the net movement of ions by the Na	extsuperscript{+}/K	extsuperscript{+} ATPase pump?

Accepted Answer

$$3\ 	ext{Na}^{+}_{	ext{out}} : 2\ 	ext{K}^{+}_{	ext{in}}$$

Question 15

Which of the following is a property of voltage-gated sodium channels that is essential for the refractory period?

Accepted Answer

They become inactivated after opening, preventing immediate reopening.

Question 16

A patient with multiple sclerosis experiences demyelination of axons. Which symptom is most likely related to this process?

Accepted Answer

Slower or blocked nerve signal transmission.

Question 17

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

Accepted Answer

Graded potentials can summate, while action potentials cannot.

Question 18

If the extracellular concentration of K	extsuperscript{+} increases, what effect would this have on the resting membrane potential?

Accepted Answer

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

Question 19

Which of the following is a consequence of the decremental nature of graded potentials?

Accepted Answer

Graded potentials decrease in strength as they move away from the site of origin.

Cellular Physiology: Graded Potentials and Action Potentials

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