Nerve Fiber Properties MCQ Quiz | Nerve-Muscle

Welcome to the Nerve Fiber Properties quiz, specifically designed for MBBS students studying Nerve-Muscle physiology. This quiz will test your understanding of fundamental concepts such as action potential propagation, saltatory conduction, classification of nerve fibers, the all-or-none law, and factors influencing nerve excitability and conductivity. You will encounter 25 multiple-choice questions that cover high-yield topics essential for your examinations. After completing the quiz, you can submit your answers to see your score and review the correct responses, which will be highlighted for your learning. For offline revision, you can also download all the questions and their correct answers in a convenient PDF format. Good luck!

1. The “all-or-none law” of nerve conduction states that:

The amplitude of the action potential increases with the strength of the stimulus.

A sub-threshold stimulus can generate a smaller action potential.

If a stimulus is strong enough to generate an action potential, the impulse is conducted at a constant and maximum amplitude.

The law applies to the entire nerve trunk, not individual fibers.

2. Saltatory conduction is characterized by:

Action potentials being generated continuously along the axon.

Slower conduction velocity compared to unmyelinated fibers of the same diameter.

Action potentials ‘jumping’ from one node of Ranvier to the next.

High energy expenditure due to constant ion pumping along the entire axon length.

3. According to the Erlanger and Gasser classification, which nerve fibers have the fastest conduction velocity?

A-alpha (Aα) fibers

A-delta (Aδ) fibers

B fibers

C fibers

4. The absolute refractory period is primarily caused by:

The slow closing of voltage-gated K+ channels.

The inactivation of voltage-gated Na+ channels.

The hyperpolarization phase of the action potential.

The activity of the Na+/K+ pump.

5. In the context of nerve excitability, what is Chronaxie?

The minimum stimulus strength required to elicit a response.

The minimum duration for which a rheobasic current must be applied to produce a response.

The time required for a stimulus of twice the rheobasic strength to excite the nerve.

The voltage at which 50% of nerve fibers are activated.

6. Wallerian degeneration refers to the process where:

The neuron cell body swells and undergoes chromatolysis.

The portion of the axon distal to an injury degenerates.

The myelin sheath regenerates in the central nervous system.

A nerve fiber fails to conduct impulses due to fatigue.

7. Which of the following factors would INCREASE the conduction velocity of a nerve fiber?

Decreased axon diameter

Absence of a myelin sheath

Increased thickness of the myelin sheath

Lowering the temperature

8. C fibers are responsible for transmitting which type of sensation?

Proprioception and fine touch

Sharp, localized pain and cold temperature

Somatic motor impulses to skeletal muscles

Dull, aching, poorly localized pain and warmth

9. The myelin sheath in the peripheral nervous system (PNS) is formed by:

Oligodendrocytes

Schwann cells

Astrocytes

Microglia

10. A compound action potential recorded from a whole nerve is graded (not all-or-none) because:

Individual axons can produce action potentials of varying sizes.

It represents the algebraic summation of action potentials from many fibers with different thresholds and conduction velocities.

The stimulus artifact interferes with the recording.

The recording electrodes are placed too far apart.

11. Local anesthetics like lidocaine exert their effect by:

Blocking voltage-gated K+ channels

Enhancing the activity of the Na+/K+ pump

Blocking voltage-gated Na+ channels

Inhibiting neurotransmitter release at the synapse

12. Which of the following conditions increases nerve excitability by lowering the threshold for action potential generation?

Hypercalcemia

Hypokalemia

Hypocalcemia

Acidosis

13. The phenomenon where a nerve fiber shows a diminished response to a prolonged, constant stimulus is known as:

Summation

Refractory period

Accommodation (Adaptation)

Potentiation

14. Rheobase is defined as the minimum:

Time required to stimulate a nerve with a current of twice the rheobasic strength.

Current strength that produces a response, regardless of stimulus duration.

Voltage that causes tetany in the innervated muscle.

Current strength that, when applied for an infinite duration, is just sufficient to excite the tissue.

15. The propagation of an action potential in an unmyelinated axon is best described as:

Saltatory conduction

Continuous conduction via local circuit currents

Decremental conduction

Synaptic transmission

16. A-delta (Aδ) fibers are primarily associated with the sensation of:

Dull, throbbing pain

Proprioception

Sharp, pricking pain and cold temperature

Preganglionic autonomic signals

17. During the relative refractory period, a second action potential can be generated, but it requires:

A stimulus of normal threshold intensity.

A sub-threshold stimulus.

A stimulus that is stronger than the normal threshold (suprathreshold).

A chemical stimulus instead of an electrical one.

18. The nodes of Ranvier are critical for saltatory conduction because they:

Are the only sites where the Na+/K+ pump is located.

Contain a high density of voltage-gated Na+ channels.

Are covered by a thicker layer of myelin.

Lack voltage-gated channels entirely.

19. Which statement accurately describes B fibers?

They are unmyelinated and conduct impulses for dull pain.

They are the largest diameter fibers and innervate skeletal muscle.

They are myelinated and serve as preganglionic autonomic fibers.

They have the slowest conduction velocity of all fiber types.

20. The strength-duration curve illustrates the relationship between:

The amplitude of an action potential and the duration of the stimulus.

The intensity of a stimulus and the duration it must be applied to be effective.

The frequency of action potentials and the strength of the sensation.

The conduction velocity and the diameter of the nerve fiber.

21. The property of a nerve fiber to transmit an impulse along its entire length without any change in its properties is called:

Excitability

Conductivity

Refractoriness

Indefatigability

22. Nerve fibers are considered ‘indefatigable’ primarily because:

They have a very large store of ATP.

The ionic changes with each action potential are very small, and the Na+/K+ pump efficiently restores gradients.

Neurotransmitter synthesis is the rate-limiting step.

They switch to anaerobic metabolism during high activity.

23. In the CNS, regeneration of axons after injury is severely limited, partly due to:

The absence of Schwann cells and the presence of inhibitory factors from oligodendrocytes and astrocytes.

The rapid formation of a blood clot at the injury site.

The high metabolic rate of CNS neurons.

The lack of a blood-brain barrier in the injured area.

24. The rapid depolarization phase of the action potential in a neuron is caused by the influx of which ion?

K+ (Potassium)

Ca2+ (Calcium)

Cl- (Chloride)

Na+ (Sodium)

25. A lower chronaxie value for a nerve indicates:

Lower excitability

A higher rheobase

Higher excitability

The nerve is unmyelinated

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Nerve Fiber Properties MCQ Quiz | Nerve-Muscle

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