Question 1

Which property of ion channels determines how many ions can pass through per unit time, and is mathematically described by conductance ($g$)?

Accepted Answer

Permeability

Question 2

A neuron’s membrane potential ($V_m$) changes due to the opening of voltage-gated Na$^+$ channels. What is the immediate effect on ionic currents and membrane potential?

Accepted Answer

Na$^+$ influx increases, causing depolarization

Question 3

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

Accepted Answer

Graded potentials are slow and analog, while action potentials are fast and digital

Question 4

During an action potential, which pharmacological agent would you use to isolate K$^+$ currents, and what is its mechanism?

Accepted Answer

TEA; blocks K$^+$ channels

Question 5

What is the primary reason myelination increases the speed of action potential propagation in axons?

Accepted Answer

Myelin decreases membrane capacitance and increases effective membrane thickness, increasing conduction velocity

Question 6

Which equation best describes the relationship between conduction velocity ($v$), axial resistance ($r_a$), and membrane capacitance ($c_m$) in an axon?

Accepted Answer

$v = 1 / (r_a 	imes c_m)$

Question 7

A patient with Multiple Sclerosis experiences impaired motor function. Which physiological process is most directly affected?

Accepted Answer

Saltatory conduction due to demyelination

Question 8

What is the role of the absolute refractory period in neuronal signaling?

Accepted Answer

It prevents any stimulus from triggering another action potential due to Na$^+$ channel inactivation

Question 9

Which of the following best explains the positive feedback cycle during the initiation of an action potential?

Accepted Answer

Depolarization opens Na$^+$ channels, which causes more depolarization and further Na$^+$ channel opening

Question 10

A voltage clamp experiment is used to study ion channel kinetics. If the membrane potential is held constant and a rapid inward current is observed, which ion is most likely responsible?

Accepted Answer

Na$^+$

Question 11

Which statement about the gating of ion channels is correct?

Accepted Answer

Gating refers to the opening and closing of ion channels in response to stimuli such as voltage, ligand, or mechanical force

Question 12

If a neuron’s axon diameter is increased, what is the expected effect on conduction velocity, assuming all other factors remain constant?

Accepted Answer

Conduction velocity increases due to decreased axial resistance

Question 13

Which type of ionic current is characterized by slow activation and little inactivation during an action potential?

Accepted Answer

K$^+$ current

Question 14

What is the effect of TEA (tetraethylammonium) on neuronal ionic currents during an action potential?

Accepted Answer

It blocks K$^+$ currents

Question 15

Which of the following is a key feature of action potentials that distinguishes them from graded potentials?

Accepted Answer

Action potentials are all-or-none events

Question 16

A neuron is exposed to TTX (tetrodotoxin). What is the expected effect on action potential generation?

Accepted Answer

Action potentials are blocked due to inhibition of Na$^+$ channels

Question 17

Which property of ion channels is most directly responsible for their ability to allow only certain ions to pass through?

Accepted Answer

Selectivity

Question 18

During the relative refractory period, which of the following is true?

Accepted Answer

Some Na$^+$ channels have recovered, but a stronger-than-normal stimulus is required to trigger another action potential

Question 19

Which of the following best describes saltatory conduction?

Accepted Answer

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

Question 20

A mutation in an ion channel protein leads to a disease known as a channelopathy. Which aspect of neuronal function is most likely to be affected?

Accepted Answer

Action potential generation and propagation

Membrane Potentials and Ion Channel Physiology

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