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Question #47412
The Question
A patient suffers from a neurodegenerative disorder that selectively destroys the myelin sheath of somatic motor neurons, severely impairing saltatory conduction. Concurrently, the patient develops severe hypocalcemia. Which of the following best describes the state of the skeletal muscles and the underlying physiological mechanism at the neuromuscular junction (NMJ)?
Options
- A.
The muscles will exhibit tetany because hypocalcemia lowers the threshold for action potentials directly in the sarcolemma, bypassing the need for acetylcholine.
- B.
The muscles will experience flaccid paralysis because the decay of the action potential prevents the opening of voltage-gated Ca2+ channels at the pre-synaptic terminal.
- C.
The muscles will undergo spastic paralysis because the loss of myelin causes continuous, unregulated influx of Na+ along the entire axon length.
- D.
The muscles will exhibit tetany because the impaired nerve conduction directly inhibits the reuptake of Ca2+ by the sarcoplasmic reticulum.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Acetylcholine|Na+-K+ Pump|Nodes_of_Ranvier
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: The 'Hypocalcemia = Tetany' reflex.
Students memorize this direct association from the NCERT 'Disorders of Muscular and Skeletal System' section.
However, they often fail to integrate it with neurophysiology.
Tetany is driven by hyperexcitable motor neurons firing spontaneously.
If the axon cannot conduct the action potential to the terminal (due to demyelination), the signal is lost.
The NMJ remains silent, leading to paralysis, which effectively masks the hypocalcemia-induced tetany.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Locomotion and Movement - Class 11 |
| Concept | Tetany Logic |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |