Question 1

During the depolarization phase of an action potential, which of the following best describes the movement of ions across the neuronal membrane?

Accepted Answer

Sodium ions ($Na^+$) rapidly enter the axon, making the inside more positive.

Question 2

Which of the following best explains why action potentials are considered 'all-or-none' events?

Accepted Answer

Action potentials only occur if the membrane potential reaches a specific threshold value.

Question 3

A patient presents with hyponatremia (low $Na^+$ in the interstitial fluid) due to extreme dehydration. What effect would this have on neuronal action potentials?

Accepted Answer

Action potentials would be inhibited because there is insufficient $Na^+$ to depolarize the membrane.

Question 4

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

Accepted Answer

Action potentials maintain their amplitude as they travel, while decremental conduction decreases in amplitude over distance.

Question 5

Saltatory conduction is faster than continuous conduction because:

Accepted Answer

Action potentials jump from one node of Ranvier to the next, skipping myelinated regions.

Question 6

Which of the following events occurs at the synaptic knob during neurotransmission?

Accepted Answer

Voltage-gated $Ca^{2+}$ channels open, allowing $Ca^{2+}$ to enter and trigger neurotransmitter release.

Question 7

Which of the following is NOT a characteristic of a neurotransmitter?

Accepted Answer

It is always deactivated by reuptake into the postsynaptic cell.

Question 8

Which of the following mechanisms can terminate the action of a neurotransmitter in the synaptic cleft?

Accepted Answer

Enzymatic breakdown, reuptake into the presynaptic neuron, and diffusion away from the synaptic cleft.

Question 9

A poison that blocks the $Na^+/K^+$ pump would have which effect on neuronal action potentials?

Accepted Answer

It would prevent the restoration of the resting membrane potential, eventually inhibiting further action potentials.

Question 10

Which type of neuronal circuit is best described as one input neuron stimulating multiple output neurons, amplifying the signal?

Accepted Answer

Diverging circuit

Question 11

Which neuronal circuit type is most likely to be involved in rhythmic activities such as breathing?

Accepted Answer

Reverberating circuit

Question 12

Which of the following best describes the role of the threshold potential in the generation of an action potential?

Accepted Answer

It is the membrane potential at which voltage-gated $Na^+$ channels open, initiating depolarization.

Question 13

During repolarization of the action potential, which ion movement is primarily responsible for returning the membrane potential to a negative value?

Accepted Answer

$K^+$ ions exit the axon through voltage-gated channels.

Question 14

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

Accepted Answer

Myelin insulates the axon, allowing action potentials to jump between nodes of Ranvier (saltatory conduction).

Question 15

Which of the following is an example of a parallel-after-discharge neuronal circuit?

Accepted Answer

A single input neuron stimulates several pathways that converge on a single output neuron, causing a burst of impulses.

Question 16

Which of the following would most likely result from a drug that inhibits acetylcholinesterase at the synaptic cleft?

Accepted Answer

Prolonged action of acetylcholine, leading to continuous stimulation of the postsynaptic cell.

Question 17

Which of the following best describes the process of neurotransmitter reuptake?

Accepted Answer

Neurotransmitters are actively transported back into the presynaptic neuron for reuse.

Question 18

A patient is given a selective serotonin reuptake inhibitor (SSRI). What is the expected effect at the synaptic cleft?

Accepted Answer

Increased serotonin levels in the synaptic cleft due to inhibited reuptake.

Question 19

Which of the following best describes the change in membrane potential during hyperpolarization?

Accepted Answer

The membrane potential becomes more negative than the resting membrane potential ($RMP$).

Neuromuscular Physiology II: Action Potentials, Synaptic Transmission, and Neuronal Circuits

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