Question 1

Which of the following best describes the role of potassium ($$K^+) in $$generating the resting membrane potential of a neuron?

Accepted Answer

Potassium ions diffuse out of the cell through leakage channels, making the inside of the cell more negative and establishing the resting membrane potential.

Question 2

Which equation is commonly used to calculate the equilibrium potential for a specific ion across a membrane?

Accepted Answer

$$E_{ion} = \frac{RT}{zF} \ln \left( \frac{[ion]_{out}}{[ion]_{in}} \right)$$

Question 3

A neuron is exposed to a drug that blocks voltage-gated sodium ($$Na^+) $$channels. What is the most likely effect on the neuron's ability to generate an action potential?

Accepted Answer

The neuron will be unable to depolarize and thus cannot generate an action potential.

Question 4

Which of the following types of ion channels open in response to physical deformation of the receptor?

Accepted Answer

Mechanically gated channels

Question 5

During the repolarization phase of an action potential, which of the following events occurs?

Accepted Answer

Voltage-gated $$K^+$$ channels open, allowing $$K^+ to $$exit the cell.

Question 6

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

Accepted Answer

Large anionic proteins are trapped inside the cell and the membrane is more permeable to $$K^+$$ than $$Na^+$$, resulting in a net negative charge.

Question 7

Which of the following is TRUE regarding graded potentials?

Accepted Answer

They decay with distance and are short-lived, localized changes in membrane potential.

Question 8

The sodium-potassium pump ($$Na^+/K^+$$ ATPase) maintains the resting membrane potential by:

Accepted Answer

Pumping three $$Na^+$$ ions out and two $$K^+$$ ions in per ATP hydrolyzed.

Question 9

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

Accepted Answer

Once threshold is reached, an action potential is always generated with the same amplitude.

Question 10

Saltatory conduction is characterized by:

Accepted Answer

Action potentials jumping from one node of Ranvier to the next in myelinated axons.

Question 11

Multiple sclerosis (MS) affects neural conduction by:

Accepted Answer

Destroying myelin sheaths in the CNS, leading to impaired conduction and symptoms such as weakness and visual disturbances.

Question 12

Which of the following factors increases the conduction velocity of an action potential along an axon?

Accepted Answer

Increased axon diameter and presence of myelination.

Question 13

During the depolarization phase of an action potential, which gates are open?

Accepted Answer

Voltage-gated $$Na^+$$ activation gates

Question 14

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

Accepted Answer

Voltage-gated $$Na^+$$ channels become inactivated after opening, preventing backward propagation.

Question 15

A neuron is exposed to a toxin that increases the permeability of the membrane to $$Na^+. $$What is the most likely effect on the resting membrane potential?

Accepted Answer

The resting membrane potential will become less negative (depolarized).

Question 16

Which of the following is NOT a mechanism by which ion channels can be gated?

Accepted Answer

Active transport by ATP hydrolysis

Question 17

Which of the following statements about the sodium-potassium pump ($$Na^+/K^+$$ ATPase) is correct?

Accepted Answer

It requires ATP to function and helps maintain the resting membrane potential.

Question 18

Which of the following changes in membrane potential would most likely increase the probability of a neuron firing an action potential?

Accepted Answer

Depolarization

Question 19

A patient presents with symptoms of muscle weakness and loss of coordination. MRI reveals demyelination in the CNS. Which disease is most consistent with these findings?

Accepted Answer

Multiple sclerosis (MS)

Nervous System Physiology: Membrane Potentials and Action Potentials

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