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Question #45778

Difficulty: 8/10 | 🟢 Free

The Question

In a specific autoimmune neuropathy, a patient exhibits severe skeletal muscle paralysis. Electrophysiological studies reveal that an action potential is successfully generated at the axon hillock of the motor neuron but dissipates before reaching the neuromuscular junction. Consequently, the sarcoplasmic reticulum fails to release $Ca^{2+}$ despite having normal reserves, and the sarcomeres remain structurally intact. Which of the following structures is most likely targeted by the autoantibodies, and what is the immediate physiological disruption?

Options

A.
Schwann cells; disrupting saltatory conduction at the Nodes of Ranvier, preventing the depolarization wave from reaching the T-tubules.
B.
Acetylcholine receptors on the motor end plate; preventing sarcolemma depolarization and subsequent excitation-contraction coupling.
C.
Voltage-gated $Ca^{2+}$ channels at the synaptic knob; inhibiting the influx of calcium required for the exocytosis of neurotransmitter vesicles.
D.
Sarcoplasmic reticulum membrane proteins; preventing the efflux of $Ca^{2+}$ into the sarcoplasm even when the T-tubules are successfully depolarized.

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

Sarcomere Functional Boundaries|Saltatory Conduction Nodes|Primary vs Secondary Immune Response

Why This Question Is Tricky

Common Mistakes

Conceptual Pivot: The student must distinguish between axonal conduction failure (demyelination) and synaptic transmission failure (Myasthenia Gravis).

The 'Trap' relies on the strong NCERT association between 'autoimmune skeletal muscle paralysis' and Myasthenia Gravis (Option B).

Students who rely on keyword matching rather than reading the specific electrophysiological clue ('dissipates before reaching the neuromuscular junction') will incorrectly choose B.

Quick Facts About This Question

Question Information

Subject	Biology
Chapter	Locomotion and Movement - Class 11
Concept	Sarcomere Functional Boundaries
Difficulty	8
Cognitive Load	5
Target Solve Time	120 sec
Access	Free