Q: Which of the following equations correctly represents the net movement of ions by the sodium-potassium pump during one cycle?

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

Question 1

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

Accepted Answer

Local potentials travel short distances and are graded, while action potentials travel the entire length of the axon and are all-or-none.

Question 2

A neuron at rest has a membrane potential of approximately $$-70\ \mathrm{mV}. $$What is the primary mechanism responsible for maintaining this resting membrane potential?

Accepted Answer

The activity of the sodium-potassium pump, which moves $$3\ \mathrm{Na}^+$$ out and $$2\ \mathrm{K}^+ in $$per ATP hydrolyzed.

Question 3

During which phase of the action potential do voltage-gated sodium channels inactivate and voltage-gated potassium channels open, leading to repolarization?

Accepted Answer

Repolarization phase

Question 4

A patient receives a local anesthetic such as lidocaine during a dental procedure. Which of the following best explains how this drug prevents the sensation of pain?

Accepted Answer

It blocks voltage-gated sodium channels, preventing depolarization and the generation of action potentials.

Question 5

Which of the following best describes the absolute refractory period of a neuron?

Accepted Answer

A period when no additional stimulus, no matter how strong, can initiate another action potential because voltage-gated sodium channels are inactivated.

Question 6

Which type of ion channel opens in response to the binding of a neurotransmitter such as acetylcholine?

Accepted Answer

Ligand-gated channel

Question 7

A neuron is exposed to a stimulus that causes positive charges to enter the cytosol, making the membrane potential less negative. What is this process called?

Accepted Answer

Depolarization

Question 8

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

Accepted Answer

Myelin allows for saltatory conduction, where the action potential 'jumps' from one node of Ranvier to the next, reducing the number of regions that must be depolarized.

Question 9

A patient with multiple sclerosis (MS) experiences muscle weakness and sensory disturbances. Which of the following best explains the underlying cause of these symptoms?

Accepted Answer

Loss of the myelin sheath around axons in the central nervous system, leading to impaired action potential conduction.

Question 10

Which of the following equations correctly represents the net movement of ions by the sodium-potassium pump during one cycle?

Accepted Answer

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

Question 11

Which of the following best describes the state of a voltage-gated sodium channel during the inactivated state?

Accepted Answer

Activation gate is open, inactivation gate is closed.

Question 12

A neuron receives a stimulus that causes the membrane potential to become more negative than the resting potential. Which of the following best describes this event?

Accepted Answer

Hyperpolarization

Question 13

Which of the following is true regarding the propagation of action potentials in Type A, B, and C fibers?

Accepted Answer

Type A fibers are the fastest due to their large diameter and myelination, while Type C fibers are the slowest due to their small diameter and lack of myelination.

Question 14

If a neuron is exposed to a toxin that selectively blocks potassium leak channels, what would be the most likely effect on the resting membrane potential?

Accepted Answer

The resting membrane potential would become more positive (depolarized).

Question 15

A neuron is stimulated at its dendrites, causing a local potential. Which of the following properties distinguishes this local potential from an action potential?

Accepted Answer

Local potentials are decremental and reversible, while action potentials are not.

Question 16

During saltatory conduction, where does the action potential regenerate along a myelinated axon?

Accepted Answer

At the nodes of Ranvier, where voltage-gated sodium channels are concentrated.

Question 17

A neuron is in the relative refractory period. Which of the following is true?

Accepted Answer

A stronger-than-normal stimulus is required to initiate another action potential because the membrane is hyperpolarized.

Question 18

Which of the following best explains why a neuron cannot fire a second action potential during the absolute refractory period?

Accepted Answer

The sodium channels are inactivated and cannot be reopened until they return to the resting state.

Question 19

A patient presents with a loss of sensation and muscle weakness in the lower limbs. MRI reveals demyelination in the CNS. Which of the following is the most likely diagnosis?

Accepted Answer

Multiple sclerosis

Question 20

Which of the following best describes the effect of increasing axon diameter on the speed of action potential conduction?

Accepted Answer

It decreases resistance and speeds up conduction.

Electrophysiology of Neurons: Principles, Ion Channels, and Membrane Potentials - 11.3

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