Question 1

Which of the following best describes the property of action potentials in neurons?

Accepted Answer

They are constant in magnitude and duration, independent of stimulus intensity.

Question 2

A nerve impulse is generated only if the stimulus exceeds a certain threshold value. What happens to the membrane potential during the peak of an action potential?

Accepted Answer

It rises to about $$+30\,mV.$$

Question 3

Which structure in a neuron is primarily responsible for conducting electrical impulses away from the cell body?

Accepted Answer

Axon

Question 4

In the vertebrate nervous system, how is the action potential typically transmitted across the synapse?

Accepted Answer

By the release and diffusion of a chemical substance

Question 5

If a steady voltage $$V_0 is $$applied at one point in the axon membrane, the voltage at a distance $$x$$ from the point of application is given by $$V(x) = V_0$ e$$^{-x/\lambda}$$. If $$\lambda = 0.8\,mm$$, what percentage of V_0$ remains at x = 0.8$$\,mm$$?

Accepted Answer

37%

Question 6

Which of the following is NOT a class of neuron described in the study materials?

Accepted Answer

Glial neuron

Question 7

During an experiment, a probe is inserted into an axon and a voltage is measured as a function of time. Which phase of the action potential is characterized by a rapid decrease in potential to about $$-90\,mV$$?

Accepted Answer

Hyperpolarization

Question 8

Which of the following best explains why the action potential is considered 'all-or-none'?

Accepted Answer

Once the threshold is reached, the action potential always has the same magnitude and duration.

Question 9

Which property of axons allows fast-acting axons to propagate pulses at speeds up to $$100\,m/s$$?

Accepted Answer

Low internal resistance and specialized structure (e.g., myelination)

Question 10

A patient is exposed to a toxin that blocks the release of neurotransmitters at the synapse. What is the most likely effect on neural communication?

Accepted Answer

The action potential will not be transmitted to the adjacent cell.

Question 11

Which of the following best describes the function of interneurons?

Accepted Answer

They transmit information between neurons.

Question 12

In the axon circuit model, which electrical component represents the membrane capacitance?

Accepted Answer

A capacitor in parallel with the membrane

Question 13

Which of the following is a correct statement about muscle fibers and action potentials?

Accepted Answer

The shape of the action potential in muscle fibers is the same as in neurons, but its duration is usually longer.

Question 14

A researcher applies a steady voltage $$V_0 to an $$axon and measures the voltage at various distances. If the voltage at $$x = 1.6\,mm is$$ $$V_0$$ $$e^{-2}$$, what is the value of $$\lambda$$?

Accepted Answer

$$0.8\,mm$$

Question 15

Which of the following is NOT a typical stimulus that can elicit a nerve impulse?

Accepted Answer

Change in atmospheric pressure

Question 16

What is the typical duration of an action potential in a muscle fiber?

Accepted Answer

$$20\,msec$$

Question 17

Which of the following best describes the role of dendrites in a neuron?

Accepted Answer

They receive input signals from other neurons.

Question 18

If the voltage at a point on the axon membrane is $$V_0$$, what is the voltage at a distance $$x if$$ $$\lambda = 0.8\,mm$$ and $$x = 2.4\,mm$$?

Accepted Answer

$$V_0$$ $$e^{-3}$$

Question 19

Which of the following statements about the synaptic gap is correct?

Accepted Answer

It is about $$1\,nm = 10$$^{-9}$$\,m$$ wide.

Biophysics: Electrobiology of Neurons and Axons

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