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Question #45791
The Question
Myasthenia gravis is an autoimmune disorder that leads to progressive weakening and paralysis of skeletal muscles. During a physiological assessment of a patient's neuromuscular junction (NMJ), it is observed that motor neuron action potentials are normal, yet the muscle fails to contract. Which of the following represents the exact physiological bottleneck in this condition?
Options
- A.
Depletion of acetylcholine in the presynaptic synaptic vesicles due to rapid motor nerve stimulation.
- B.
Autoimmune destruction of acetylcholinesterase in the synaptic cleft, causing prolonged depolarization.
- C.
Reduced density of functional acetylcholine receptors on the sarcolemma, resulting in a sub-threshold end-plate potential.
- D.
Direct inhibition of voltage-gated Ca2+ channels on the sarcoplasmic reticulum by circulating autoantibodies.
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
Neuromuscular Junction Signal|Primary vs Secondary Immune Response|Neurotransmitter Receptor Specificity
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Understanding the threshold phenomenon at the motor end-plate.
Students often memorize 'NMJ disorder' but fail to distinguish between presynaptic (ACh release), synaptic (AChE activity), and postsynaptic (receptor density and EPP generation) defects.
The trap in Option D exploits a location misconception, confusing the sarcolemma with the sarcoplasmic reticulum.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Locomotion and Movement - Class 11 |
| Concept | Neuromuscular Junction Signal |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |