Question 1

Which of the following best describes the function of the myelin sheath in neuronal physiology?

Accepted Answer

It increases the speed of nerve impulse conduction along the axon by enabling saltatory conduction.

Question 2

A patient is given tetrodotoxin (TTX), which blocks voltage-gated sodium channels. What is the most likely effect on neuronal function?

Accepted Answer

Action potentials cannot be generated, leading to loss of neuronal signaling.

Question 3

Which equation best represents the electrochemical gradient for an ion across a neuronal membrane?

Accepted Answer

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

Question 4

During the repolarization phase of an action potential, which of the following occurs?

Accepted Answer

Voltage-gated potassium channels open, allowing $$K^+ to $$exit the cell.

Question 5

Which glial cell type is responsible for producing myelin in the central nervous system (CNS)?

Accepted Answer

Oligodendrocytes

Question 6

A neuron is at rest with a membrane potential of $$-70\ \mathrm{mV}. $$Which of the following best explains why the inside of the neuron is negative relative to the outside?

Accepted Answer

There is a higher concentration of $$K^+$$ inside and $$Na^+$$ outside, and the membrane is more permeable to $$K^+.$$

Question 7

Which of the following best describes the 'all-or-nothing' principle of action potentials?

Accepted Answer

An action potential either occurs fully or not at all, depending on whether threshold is reached.

Question 8

A patient is administered lidocaine, a reversible sodium channel blocker, during a dental procedure. What is the physiological effect at the site of injection?

Accepted Answer

Local neurons cannot generate action potentials, resulting in temporary loss of sensation.

Question 9

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

Accepted Answer

Action potentials jump between nodes of Ranvier in a process called saltatory conduction.

Question 10

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

Accepted Answer

No new action potential can be initiated, regardless of stimulus strength.

Question 11

Which of the following best describes the role of the sodium-potassium ATPase pump in maintaining the resting membrane potential?

Accepted Answer

It moves 3 $$Na^+$$ ions out and 2 $$K^+$$ ions into the cell, using ATP.

Question 12

A neuron receives a subthreshold stimulus. What is the most likely outcome?

Accepted Answer

No action potential is generated.

Question 13

Which of the following best describes graded potentials?

Accepted Answer

They are localized changes in membrane potential that vary with stimulus intensity.

Question 14

A researcher applies a drug that increases the permeability of the neuronal membrane to $$K^+. $$What is the most likely effect on the resting membrane potential?

Accepted Answer

The membrane potential becomes more negative (hyperpolarized).

Question 15

Which of the following events occurs at the synaptic terminal when an action potential arrives?

Accepted Answer

Voltage-gated calcium channels open, allowing $$Ca^{2+} to $$enter the terminal.

Question 16

Which of the following best explains why the frequency of action potentials encodes stimulus intensity?

Accepted Answer

A stronger stimulus increases the rate at which action potentials are generated.

Question 17

A patient with multiple sclerosis has demyelination of CNS axons. Which of the following symptoms is most likely explained by this pathology?

Accepted Answer

Slowed or blocked nerve impulse conduction, leading to muscle weakness.

Question 18

Which of the following is a correct sequence of events during an action potential?

Accepted Answer

Depolarization, repolarization, hyperpolarization

Question 19

Which of the following best describes the function of astrocytes in the central nervous system?

Accepted Answer

They provide structural and metabolic support for neurons.

Question 20

A neuron is exposed to a toxin that irreversibly blocks voltage-gated sodium channels. Which of the following best predicts the long-term effect on the neuron?

Accepted Answer

The neuron will be unable to generate or propagate action potentials.

Neuronal Physiology: Structure and Function of Neurons and Nervous System Cells

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