Question 1

Which of the following best describes the role of the sodium-potassium ATPase pump in maintaining the resting membrane potential of a neuron?

Accepted Answer

It actively pumps three sodium ions out and two potassium ions in, creating a net negative charge inside the cell.

Question 2

What is the typical resting membrane potential of a neuron, and which ions are most responsible for establishing this potential?

Accepted Answer

Resting potential is $-65\ \mathrm{mV}$, established mainly by potassium ions and negatively charged organic compounds.

Question 3

During the depolarization phase of an action potential, which event occurs at the neuronal membrane?

Accepted Answer

Voltage-gated sodium channels open, allowing Na$^+$ to rush in.

Question 4

Which property of action potentials ensures that the signal does not diminish as it travels down the axon?

Accepted Answer

All-or-nothing principle

Question 5

What is the main difference between the absolute and relative refractory periods of an action potential?

Accepted Answer

During the absolute refractory period, no action potential can be triggered regardless of stimulus strength; during the relative refractory period, a stronger stimulus is required to trigger another action potential.

Question 6

Which equation best represents the electrochemical gradient that drives ion movement across the neuronal membrane?

Accepted Answer

$E = RT/zF \ln([\mathrm{ion}]_{\mathrm{out}}/[\mathrm{ion}]_{\mathrm{in}})$

Question 7

A neuron receives multiple excitatory postsynaptic potentials (EPSPs) at different locations simultaneously. What is this process called, and what is its effect?

Accepted Answer

Spatial summation; increases the likelihood of an action potential by combining inputs from multiple sites.

Question 8

What is the effect of myelination on the propagation of action potentials along an axon?

Accepted Answer

It allows action potentials to jump between nodes of Ranvier, increasing conduction velocity.

Question 9

Which of the following best explains why the inside of a neuron is more negative than the outside at rest?

Accepted Answer

Negatively charged organic molecules and leaky potassium channels allow K$^+$ to exit, leaving behind negative charge.

Question 10

If a neuron is exposed to a toxin that blocks voltage-gated sodium channels, what would be the most immediate effect?

Accepted Answer

The neuron would be unable to generate action potentials.

Question 11

Which of the following is true about postsynaptic potentials?

Accepted Answer

They are brief, graded changes in the resting potential that can be excitatory or inhibitory.

Question 12

A neuron receives a series of EPSPs in rapid succession at the same synapse. What is this process called, and what is its effect?

Accepted Answer

Temporal summation; increases the likelihood of an action potential by repeated stimulation at one site.

Question 13

Which of the following best describes the function of voltage-gated potassium channels during an action potential?

Accepted Answer

They open in response to depolarization and allow K$^+$ to exit the cell, repolarizing the membrane.

Question 14

Which of the following statements about the rate law for action potentials is correct?

Accepted Answer

The strength of a stimulus is represented by the rate of firing of action potentials, not their size.

Question 15

Which of the following is a real-world consequence of a genetic mutation that impairs the function of myelin in neurons?

Accepted Answer

Slower propagation of action potentials, leading to symptoms such as muscle weakness and impaired coordination.

Question 16

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 17

Which of the following is NOT a function of transmembrane proteins in neurons?

Accepted Answer

Synthesizing neurotransmitters for release into the synaptic cleft.

Question 18

Which of the following best explains the concept of electrostatic pressure in neurons?

Accepted Answer

Ions are attracted to areas of opposite charge, driving their movement across the membrane.

Question 19

A patient is given a drug that increases the permeability of the neuronal membrane to chloride ions (Cl$^-$). What is the most likely effect on neuronal excitability?

Accepted Answer

The neuron will become hyperpolarized, making it less likely to fire action potentials.

Neurophysiology: Membrane Potentials, Action Potentials, and Synaptic Transmission

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