Question 1

Which of the following best describes the function of the sodium-potassium pump ($$\mathrm{Na^+/K^+}$$ ATPase) in maintaining the resting membrane potential of a neuron?

Accepted Answer

It pumps three sodium ions out and two potassium ions in, using ATP.

Question 2

A patient is given a drug that blocks voltage-gated sodium channels. What immediate effect would this have on the generation of action potentials in neurons?

Accepted Answer

Action potentials would be inhibited, preventing nerve signal transmission.

Question 3

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

Accepted Answer

Myelinated axons use saltatory conduction, allowing action potentials to jump between nodes of Ranvier.

Question 4

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

Accepted Answer

No stimulus, regardless of strength, can initiate another action potential.

Question 5

A patient presents with muscle weakness and is found to have a disorder affecting acetylcholine receptors at the neuromuscular junction. Which process is most directly impaired?

Accepted Answer

Binding of neurotransmitter to postsynaptic receptors, leading to muscle contraction

Question 6

Which equation correctly represents the Nernst equation for calculating the equilibrium potential ($$E_{ion}) $$for a given ion?

Accepted Answer

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

Question 7

If the extracellular concentration of potassium ($$[K^+]_{out}) $$increases significantly, what is the most likely effect on the resting membrane potential of a neuron?

Accepted Answer

The resting membrane potential becomes less negative (depolarizes).

Question 8

Which of the following best describes the role of calcium ions ($$Ca^{2+}) at $$the synaptic terminal of a neuron?

Accepted Answer

They trigger the release of neurotransmitter vesicles into the synaptic cleft.

Question 9

A neuron is exposed to a toxin that prevents the reuptake of neurotransmitter from the synaptic cleft. What is the most likely effect on synaptic transmission?

Accepted Answer

The postsynaptic cell will be continuously stimulated.

Question 10

Which of the following is a correct sequence of events during chemical synaptic transmission?

Accepted Answer

Action potential arrives at axon terminal → calcium influx → vesicle fusion → neurotransmitter release

Question 11

A patient is diagnosed with multiple sclerosis, a disease that damages myelin in the central nervous system. Which of the following symptoms is most directly related to this pathology?

Accepted Answer

Slowed or blocked transmission of action potentials

Question 12

Which of the following best explains why the resting membrane potential of a neuron is closer to the equilibrium potential of potassium ($$E_K) $$than to that of sodium ($$E_{Na}$$)?

Accepted Answer

The membrane is more permeable to potassium ions at rest.

Question 13

Which of the following changes would most likely increase the speed of action potential conduction along an axon?

Accepted Answer

Increasing axon diameter and adding myelin

Question 14

A neuron is at rest with a membrane potential of $$-70\ \mathrm{mV}. If $$the membrane suddenly becomes permeable only to sodium ions ($$Na^+$$), what will happen to the membrane potential?

Accepted Answer

It will move toward the equilibrium potential of sodium ($$E_{Na}$$), becoming more positive.

Question 15

Which of the following is the primary reason why action potentials travel in only one direction along an axon?

Accepted Answer

Voltage-gated sodium channels become inactivated after opening, creating a refractory period.

Question 16

A researcher measures the membrane potential of a neuron and finds it to be $$-55\ \mathrm{mV}. $$Which of the following best describes the state of the neuron?

Accepted Answer

It is at threshold and likely to fire an action potential.

Question 17

Which of the following best describes the effect of opening ligand-gated chloride ($$Cl^-) $$channels on the postsynaptic membrane?

Accepted Answer

It causes hyperpolarization, making the neuron less likely to fire.

Question 18

A patient is given a drug that inhibits acetylcholinesterase. What is the most likely effect at the neuromuscular junction?

Accepted Answer

Increased acetylcholine in the synaptic cleft and prolonged muscle contraction

Question 19

Which of the following is a direct consequence of the opening of voltage-gated potassium channels during an action potential?

Accepted Answer

Repolarization of the membrane toward the resting potential

Fundamentals of Anatomy & Physiology: Introduction, Homeostasis, and Levels of Organization

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