Question 1

Which of the following best describes the origin of the cell membrane potential in neurons?

Accepted Answer

It results from the separation of positive and negative charges across the plasma membrane, primarily due to differences in ion concentrations.

Question 2

What is the typical resting membrane potential of a neuron, and what does the negative sign indicate?

Accepted Answer

Approximately $$-70 mV$$; the negative sign indicates more negative charges inside the cell compared to the outside.

Question 3

Which ion channel type is primarily responsible for maintaining the resting membrane potential in neurons?

Accepted Answer

Leak potassium channels

Question 4

If the plasma membrane of a neuron were freely permeable to sodium ions ($$Na^+$$), what would happen to its membrane potential?

Accepted Answer

The membrane potential would approach zero or become positive as $$Na^+$$ rushes into the cell.

Question 5

Which of the following best explains the 'all-or-none principle' of action potentials?

Accepted Answer

Once the threshold is reached, an action potential of fixed size is generated, regardless of stimulus strength.

Question 6

During the generation of an action potential, which event occurs immediately after the membrane reaches threshold ($$-60 mV$$)?

Accepted Answer

Rapid opening of voltage-gated sodium channels and depolarization

Question 7

What is the primary function of the sodium-potassium exchange pump ($$Na^+/K^+$$ ATPase) in neurons?

Accepted Answer

To actively transport $$3$$ $$Na^+$$ ions out and $$2$$ $$K^+$$ ions into the cell, maintaining the resting membrane potential

Question 8

Which of the following scenarios would most likely result in hyperpolarization of a neuron?

Accepted Answer

Opening of voltage-gated potassium channels, allowing $$K^+ to $$exit the cell

Question 9

A patient is given Chemical X, which blocks voltage-gated sodium channels in neurons. What effect will this have on neuronal function?

Accepted Answer

Neurons will be unable to generate action potentials.

Question 10

Which of the following best describes saltatory propagation of an action potential?

Accepted Answer

The action potential jumps from one node of Ranvier to the next in a myelinated axon.

Question 11

Which type of nerve fiber is most likely to carry urgent sensory information, such as pain or motor commands to skeletal muscle?

Accepted Answer

Type A fibers: large diameter, myelinated, fast propagation

Question 12

Which of the following factors increases the speed of action potential propagation along an axon?

Accepted Answer

Increasing axon diameter and adding myelin

Question 13

A graded potential is most likely to result in an action potential if:

Accepted Answer

It depolarizes the membrane to the threshold value.

Question 14

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

Accepted Answer

The refractory period prevents the membrane from responding to another stimulus immediately after an action potential.

Question 15

What would be the effect of Chemical Y, which blocks voltage-gated potassium channels in neurons?

Accepted Answer

Neurons would have prolonged action potentials due to delayed repolarization.

Question 16

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

Accepted Answer

Depolarization to threshold, activation of voltage-gated $$Na^+$$ channels, rapid depolarization, activation of voltage-gated $$K^+$$ channels, repolarization, brief hyperpolarization, return to resting potential

Question 17

Which of the following best describes a graded (local) potential?

Accepted Answer

A localized change in membrane potential that diminishes with distance from the site of stimulation.

Question 18

What is the effect of increasing extracellular potassium levels (Chemical Z) on a neuron's membrane potential?

Accepted Answer

It would reduce the potassium gradient, making the membrane potential less negative (depolarization).

Question 19

Which of the following axons is most likely myelinated: one that propagates action potentials at $$50$$ meters per second or one that carries them at $$1$$ meter per second?

Accepted Answer

The axon propagating at $$50$$ meters per second

Membrane Potential and Action Potential in Nervous Tissue

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