Q: Which equation best 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 typical neuron?

Accepted Answer

It is the region where action potentials are initiated due to a high density of voltage-gated sodium channels.

Question 2

A patient is exposed to tetrodotoxin (TTX) from puffer fish, which blocks voltage-gated sodium channels. What is the most likely effect on neuronal signaling?

Accepted Answer

Neurons will be unable to depolarize, preventing the initiation and propagation of action potentials.

Question 3

Which equation best 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 4

During the absolute refractory period of an action potential, which of the following is true?

Accepted Answer

Voltage-gated sodium channels are inactivated and no action potential can be generated.

Question 5

Which of the following best explains why myelinated axons conduct action potentials faster than unmyelinated axons?

Accepted Answer

Myelin allows action potentials to jump from node to node, a process called saltatory conduction.

Question 6

A neuron is at rest with a membrane potential of $$-70\ \mathrm{mV}. $$Which of the following best describes the distribution of ions across the membrane?

Accepted Answer

High $$\mathrm{K}^+$$ inside the cell, high $$\mathrm{Na}^+$$ outside the cell

Question 7

Which of the following scenarios would most likely result in a graded potential rather than an action potential?

Accepted Answer

A small, localized depolarization in the dendrite that does not reach threshold

Question 8

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

Accepted Answer

If threshold is reached, an action potential of fixed size is generated; if not, no action potential occurs.

Question 9

A patient with multiple sclerosis (MS) is experiencing muscle weakness and loss of vision. Which of the following best explains the underlying cause of these symptoms?

Accepted Answer

Loss of myelin sheaths around axons, impairing saltatory conduction

Question 10

Which of the following best describes the effect of an anticonvulsant drug that blocks voltage-gated sodium channels in neurons?

Accepted Answer

It prevents the initiation and propagation of action potentials, reducing neuronal excitability.

Question 11

Which of the following is a key difference between graded potentials and action potentials?

Accepted Answer

Graded potentials decrease in strength with distance, while action potentials do not lose strength as they propagate.

Question 12

A neuron receives multiple subthreshold excitatory inputs at its dendrites. What is the most likely outcome at the axon hillock?

Accepted Answer

An action potential will be generated if the inputs summate to reach threshold.

Question 13

Which of the following best explains why the resting membrane potential is negative?

Accepted Answer

The sodium-potassium pump moves more positive charges out than in, and the membrane is more permeable to $$\mathrm{K}^+$$, allowing positive charge to leave the cell.

Question 14

During which phase of the action potential do voltage-gated potassium channels open, and what is the effect?

Accepted Answer

During repolarization, causing $$\mathrm{K}^+ to $$leave the cell and the membrane potential to return toward resting

Question 15

A patient develops Guillain-Barré syndrome after a viral infection. Which of the following is the most likely effect on nerve conduction?

Accepted Answer

Slowed or blocked action potential propagation due to demyelination of peripheral nerves

Question 16

Which of the following best describes the role of ligand-gated ion channels in neuronal signaling?

Accepted Answer

They open or close in response to neurotransmitter binding and are typically found on dendrites and the cell body.

Question 17

If a neuron is hyperpolarized to $$-80\ \mathrm{mV}$$, which of the following is true regarding its excitability?

Accepted Answer

It is less likely to fire an action potential because the membrane potential is further from threshold.

Question 18

Which of the following best explains why action potentials do not lose strength as they travel along the axon?

Accepted Answer

Action potentials are regenerated at each segment of the axon by voltage-gated ion channels.

Question 19

Which of the following best describes the effect of increasing the frequency of action potential firing in a neuron?

Accepted Answer

It increases the amount of neurotransmitter released at the synapse.

Nerve Cells and Electrical Signaling: Structure, Function, and Physiology of Neurons

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