Question 1

Which of the following best describes the function of sensory neurons in the nervous system?

Accepted Answer

They receive stimuli from sensory organs and monitor the external and internal environment.

Question 2

What is the primary role of the axon in a neuron?

Accepted Answer

To conduct electrical impulses away from the cell body.

Question 3

An action potential in a neuron is characterized by which of the following voltage changes?

Accepted Answer

A sudden rise to about +30 mV followed by a rapid decrease to about -90 mV.

Question 4

Which equation describes the exponential decrease of voltage along the axon when a steady voltage $$V_0 is $$applied?

Accepted Answer

$$V(x) = V_0$ e$$^{-x/\lambda}$$

Question 5

If the length constant $$\lambda of an $$axon is 0.8 mm, what percentage of the original voltage $$V_0$$ remains at a distance of 0.8 mm from the point of application?

Accepted Answer

37%

Question 6

Which of the following is TRUE about the propagation of action potentials in neurons?

Accepted Answer

The pulse is constant in magnitude and duration, independent of stimulus intensity.

Question 7

What is the function of interneurons in the nervous system?

Accepted Answer

They transmit information between neurons.

Question 8

During an experiment, a probe is inserted into an axon to measure voltage changes. What is the most common type of stimulus used to elicit a nerve impulse in such experiments?

Accepted Answer

Externally applied voltage

Question 9

Which of the following statements about the synapse is correct?

Accepted Answer

The synapse is a gap where chemical substances are released to transmit signals.

Question 10

A nerve impulse is only produced if the stimulus exceeds a certain threshold value. What is the physiological significance of this threshold?

Accepted Answer

It prevents the neuron from firing in response to weak, irrelevant stimuli.

Question 11

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

Accepted Answer

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

Question 12

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

Accepted Answer

Glial neuron

Question 13

Muscle fibers produce and propagate electrical impulses similar to neurons. What is a key difference in their action potentials?

Accepted Answer

Muscle fiber action potentials have a longer duration (about 20 ms) than neuronal action potentials.

Question 14

If a fast-acting axon propagates a pulse at 100 m/sec, how long does it take for the pulse to travel 1 meter?

Accepted Answer

$$0.01$$ seconds

Question 15

Which of the following factors can serve as a stimulus to elicit a nerve impulse?

Accepted Answer

Injected chemical, mechanical pressure, or applied voltage

Question 16

What happens to the membrane potential immediately after the peak of the action potential?

Accepted Answer

It rapidly decreases to about -90 mV.

Question 17

Which part of the neuron receives input signals from other neurons?

Accepted Answer

Dendrites

Question 18

In the vertebrate nervous system, how is the signal usually transmitted across the synapse?

Accepted Answer

By diffusion of a chemical substance released at the nerve ending

Question 19

A researcher applies a steady voltage $$V_0 at $$one point in an axon. At a distance $$x = 2\lambda$$ from the point of application, what fraction of the original voltage remains?

Accepted Answer

$$e^{-2}$$ \approx 0.14$$

Question 20

Which of the following best describes the propagation speed of action potentials in fast-acting axons?

Accepted Answer

Up to 100 m/sec

Biophysics: Electrobiology, Nervous System, and Action Potentials

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