$$V_{m} \geq V_{threshold} \implies \text{Action potential of fixed amplitude}$$

Question 1

Which of the following best explains how local anesthetics such as lidocaine produce numbness during dental procedures?

Accepted Answer

They block voltage-gated sodium ion channels, preventing depolarization and action potential transmission.

Question 2

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

Accepted Answer

During repolarization; potassium ions exit the cell.

Question 3

A patient with multiple sclerosis experiences muscle weakness and sensory changes. Which of the following best explains the underlying cause?

Accepted Answer

Loss of myelin sheath, resulting in decreased action potential propagation speed.

Question 4

Which of the following statements about the refractory period is correct?

Accepted Answer

During the absolute refractory period, voltage-gated sodium channels are either activated or inactivated and cannot be reopened.

Question 5

Which equation best represents the all-or-none principle of action potentials?

Accepted Answer

$$V_{m} \geq V_{threshold} \implies 	ext{Action potential of fixed amplitude}$$

Question 6

Saltatory conduction is faster than continuous conduction because:

Accepted Answer

The myelin sheath allows the action potential to 'jump' between nodes of Ranvier.

Question 7

Which type of axon fiber would transmit a pain signal from the skin to the CNS most slowly?

Accepted Answer

Type C fiber

Question 8

A neuron receives a local potential that depolarizes the axolemma to −60 mV. What is the likely outcome?

Accepted Answer

No action potential will occur because the threshold is not reached.

Question 9

Which of the following best describes the difference between local and action potentials?

Accepted Answer

Local potentials are decremental and reversible, while action potentials are nondecremental and irreversible.

Question 10

Which of the following scenarios best illustrates the concept of self-propagation in action potentials?

Accepted Answer

A single action potential triggers another in the adjacent section of the axon, continuing down to the axon terminal.

Question 11

Which of the following is a real-world consequence of blocking sodium ion channels in both neurons and muscle cells during a dental procedure?

Accepted Answer

Temporary numbness and possible weakness or paralysis of the affected muscles.

Question 12

Which of the following best explains why action potentials only travel in one direction along an axon?

Accepted Answer

The previous section of the membrane is in the refractory period and cannot be re-excited immediately.

Question 13

Which of the following is true regarding electrical synapses?

Accepted Answer

They involve gap junctions that allow bidirectional flow of electric current.

Question 14

A patient is diagnosed with a disease that destroys myelin in the CNS. Which of the following would you expect to observe in their nerve conduction?

Accepted Answer

Decreased speed and possible failure of action potential propagation.

Question 15

Which of the following best describes the role of the sodium-potassium pump after an action potential?

Accepted Answer

It restores the resting membrane potential by moving sodium out and potassium in.

Question 16

Which of the following is a correct pairing of axon type and its function?

Accepted Answer

Type B fibers: sensory axons from organs and autonomic efferent fibers

Question 17

If a neuron is exposed to a toxin that keeps voltage-gated sodium channels open, what would most likely happen?

Accepted Answer

The neuron would remain depolarized and be unable to repolarize, preventing further action potentials.

Question 18

Which of the following best describes the relationship between axon diameter and conduction speed?

Accepted Answer

Larger diameter axons have lower resistance and faster conduction.

Question 19

Which of the following is a key difference between axodendritic and axosomatic synapses?

Accepted Answer

Axodendritic synapses occur between axons and dendrites, while axosomatic synapses occur between axons and cell bodies.

Action Potentials and Synaptic Transmission in Neurons

Study Guide - Practice Questions