Question 1

Which of the following best describes the role of the sodium-potassium pump ($$\mathrm{Na^+/K^+}$$ ATPase) in maintaining the resting membrane potential of a neuron?

Accepted Answer

It actively transports three $$\mathrm{Na^+}$$ ions out and two $$\mathrm{K^+}$$ ions in, maintaining the negative resting potential.

Question 2

A patient presents with a mutation that causes voltage-gated $$\mathrm{Na^+}$$ channels to remain open longer than normal. What is the most likely effect on the action potential?

Accepted Answer

The depolarization phase will be prolonged, possibly leading to excessive neuronal firing.

Question 3

Which equation correctly represents Ohm’s Law as it applies to the movement of ions across a neuronal membrane?

Accepted Answer

$$V = I 	imes R$$

Question 4

During which phase of the action potential are most voltage-gated $$\mathrm{Na^+}$$ channels inactivated and voltage-gated $$\mathrm{K^+}$$ channels open?

Accepted Answer

Repolarization

Question 5

A graded potential is most likely to occur in which part of a neuron?

Accepted Answer

Dendrites and cell body

Question 6

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

Accepted Answer

Voltage-gated $$\mathrm{Na^+}$$ channels behind the action potential are inactivated (absolute refractory period).

Question 7

If the extracellular concentration of $$\mathrm{K^+}$$ increases significantly, what is the most likely effect on the resting membrane potential?

Accepted Answer

The resting membrane potential becomes less negative (depolarized).

Question 8

Which type of ion channel opens in response to a neurotransmitter binding to its receptor?

Accepted Answer

Chemically gated (ligand-gated) channel

Question 9

A demyelinating disease such as multiple sclerosis primarily affects which aspect of neuronal signaling?

Accepted Answer

The speed of action potential propagation (conduction velocity)

Question 10

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

Accepted Answer

If threshold is reached, an action potential will fire completely; if not, it will not fire at all.

Question 11

A neuron is exposed to a toxin that blocks all voltage-gated $$\mathrm{K^+}$$ channels. What is the most likely effect on the action potential?

Accepted Answer

Repolarization will be delayed or absent, prolonging the action potential.

Question 12

Which of the following is true regarding the relationship between stimulus intensity and action potential frequency?

Accepted Answer

A stronger stimulus increases the frequency of action potentials.

Question 13

Which fiber type conducts action potentials the fastest, and why?

Accepted Answer

A fibers, because they are heavily myelinated and have the largest diameter.

Question 14

Which of the following best describes the effect of opening a chemically gated $$\mathrm{Cl^-}$$ channel on the postsynaptic membrane?

Accepted Answer

It causes hyperpolarization, decreasing the likelihood of an action potential.

Question 15

A neuron is in the relative refractory period. Which of the following is true?

Accepted Answer

Only a stronger-than-normal stimulus can trigger another action potential.

Question 16

Which of the following scenarios best illustrates the concept of a graded potential?

Accepted Answer

A neurotransmitter binds to a receptor, causing a small, localized depolarization in the dendrite.

Question 17

Which of the following best explains why graded potentials decay over distance?

Accepted Answer

Leakage of charge across the membrane causes the current to dissipate.

Question 18

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

Accepted Answer

Resting state → Depolarization → Repolarization → Hyperpolarization

Question 19

A patient is given a drug that increases the permeability of the neuronal membrane to $$\mathrm{K^+}. $$What is the most likely effect?

Accepted Answer

The neuron will hyperpolarize, making it less likely to fire an action potential.

Fundamentals of the Nervous System and Nervous Tissue: Membrane Potentials and Action Potentials

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