Question 1

Which region of a neuron is known as the 'trigger zone' for action potential initiation due to its high density of voltage-gated sodium channels?

Accepted Answer

Axon initial segment

Question 2

During the propagation of an action potential, what is the primary mechanism that allows the depolarization to move along the axon?

Accepted Answer

Local current flow between adjacent regions

Question 3

Which of the following best describes the effect of myelination on action potential conduction?

Accepted Answer

It allows action potentials to jump between nodes, increasing speed.

Question 4

If a neuron is demyelinated due to disease, what is the most likely effect on action potential propagation?

Accepted Answer

Action potentials will fail to propagate efficiently, leading to slower conduction.

Question 5

Which equation is commonly used to calculate the equilibrium potential for a particular ion across a membrane?

Accepted Answer

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

Question 6

A patient presents with symptoms of multiple sclerosis, a disease characterized by demyelination. Which of the following best explains the neurological deficits observed?

Accepted Answer

Loss of myelin disrupts saltatory conduction, slowing or blocking action potential propagation.

Question 7

Which type of glial cell is responsible for myelinating axons in the central nervous system?

Accepted Answer

Oligodendrocytes

Question 8

What is the main difference in action potential propagation between myelinated and unmyelinated axons?

Accepted Answer

Myelinated axons use saltatory conduction, while unmyelinated axons use continuous conduction.

Question 9

Which of the following best describes the role of voltage-gated sodium channels in the initiation of an action potential?

Accepted Answer

They open in response to depolarization, allowing sodium ions to enter and further depolarize the membrane.

Question 10

A neuron receives multiple graded potentials at its dendrites. What determines whether an action potential will be initiated?

Accepted Answer

Whether the sum of graded potentials at the axon hillock reaches threshold

Question 11

Which of the following is a direct consequence of the opening of voltage-gated potassium channels during an action potential?

Accepted Answer

Repolarization of the membrane

Question 12

In a myelinated axon, where are the majority of voltage-gated sodium channels located?

Accepted Answer

Concentrated at the nodes of Ranvier

Question 13

Which process is responsible for the rapid transmission of action potentials in myelinated axons?

Accepted Answer

Saltatory conduction

Question 14

If the distance between nodes of Ranvier increases, what is the most likely effect on action potential propagation?

Accepted Answer

Action potentials may fail to propagate if the distance exceeds the length constant.

Question 15

Which of the following best explains why myelination increases the speed of action potential conduction?

Accepted Answer

Myelin increases membrane resistance and decreases capacitance, allowing the action potential to jump between nodes.

Question 16

A researcher measures the conduction velocity of two axons: one myelinated and one unmyelinated. The myelinated axon conducts at 100 m/s, while the unmyelinated axon conducts at 1 m/s. What is the most likely explanation for this difference?

Accepted Answer

Saltatory conduction in the myelinated axon allows for rapid transmission.

Question 17

Which of the following is NOT a function of myelin in the nervous system?

Accepted Answer

Synthesizing neurotransmitters

Question 18

A toxin blocks voltage-gated sodium channels in neurons. What is the most immediate effect on neuronal signaling?

Accepted Answer

Action potentials cannot be initiated or propagated.

Question 19

Which of the following best describes graded potentials?

Accepted Answer

They vary in amplitude and can summate to reach threshold for action potential initiation.

Excitable Cells and Action Potentials: Structure, Initiation, and Propagation

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