Q: Which of the following equations correctly represents the action of the sodium-potassium pump in maintaining the resting membrane potential?

$3\ \mathrm{Na}^+\ \text{out} : 2\ \mathrm{K}^+\ \text{in}$

Question 1

Which of the following best describes the function of the axon hillock in a neuron?

Accepted Answer

It is the region where action potentials are initiated due to the summation of graded potentials.

Question 2

A patient is diagnosed with a genetic disorder that results in the loss of myelin in the central nervous system. Which of the following is the most likely consequence for nerve impulse conduction?

Accepted Answer

Conduction will become continuous and much slower, leading to impaired neural communication.

Question 3

Which of the following statements about the resting membrane potential (RMP) of a neuron is correct?

Accepted Answer

The RMP is maintained by the sodium-potassium pump, which moves 3 Na$^+$ out and 2 K$^+$ in, and by the membrane's greater permeability to K$^+$.

Question 4

A neuron receives a stimulus that causes the membrane potential to change from $-70\ \mathrm{mV}$ to $-60\ \mathrm{mV}$. Which term best describes this change?

Accepted Answer

Depolarization

Question 5

Which of the following best explains why action potentials are unidirectional along an axon?

Accepted Answer

The absolute refractory period prevents the backward propagation of the action potential.

Question 6

A neuron is exposed to a toxin that blocks voltage-gated sodium channels. What is the most immediate 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 7

Which of the following equations correctly represents the action of the sodium-potassium pump in maintaining the resting membrane potential?

Accepted Answer

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

Question 8

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

Accepted Answer

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

Question 9

A graded potential differs from an action potential in which of the following ways?

Accepted Answer

Graded potentials decay with distance, while action potentials do not.

Question 10

A patient presents with muscle weakness. Laboratory tests reveal a mutation that increases the number of potassium leak channels in neurons. Which of the following best explains the effect on the resting membrane potential?

Accepted Answer

The resting membrane potential will become more negative, making it harder to reach threshold for action potentials.

Question 11

Which of the following best describes the role of voltage-gated ion channels in the generation of an action potential?

Accepted Answer

They open in response to changes in membrane potential, allowing rapid influx or efflux of specific ions.

Question 12

Which of the following scenarios would most likely increase the speed of action potential propagation along an axon?

Accepted Answer

Increasing the diameter of the axon and adding a myelin sheath.

Question 13

A neuron is exposed to a drug that keeps voltage-gated sodium channels in the inactivated state. What is the most likely effect on the neuron's refractory period?

Accepted Answer

The absolute refractory period will be prolonged, preventing the generation of new action potentials.

Question 14

Which of the following best explains why the inside of a resting neuron is negative relative to the outside?

Accepted Answer

The membrane is more permeable to potassium ions, which diffuse out, leaving behind negatively charged proteins.

Question 15

A neuron is stimulated by a neurotransmitter that opens chemically gated chloride channels. What is the most likely effect on the membrane potential?

Accepted Answer

The membrane will hyperpolarize, decreasing the likelihood of an action potential.

Question 16

Which of the following is true regarding the all-or-none principle of action potentials?

Accepted Answer

Once threshold is reached, an action potential of fixed size is generated.

Question 17

During which phase of the action potential are voltage-gated sodium channels inactivated and voltage-gated potassium channels open?

Accepted Answer

Repolarization

Question 18

A neuron is exposed to a stimulus that causes a graded potential. Which of the following best describes the relationship between the strength of the stimulus and the resulting graded potential?

Accepted Answer

A stronger stimulus produces a larger graded potential that spreads farther.

Question 19

Which of the following best describes saltatory conduction?

Accepted Answer

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

2B) Neurophysiology: Structure and Function of Neurons

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