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Question #45790
The Question
A patient suffers from severe flaccid paralysis after consuming improperly canned food. Nerve conduction studies reveal that action potentials reach the axon terminals of motor neurons normally, but there is a complete absence of acetylcholine release into the synaptic cleft. However, the postsynaptic muscle membrane responds normally to artificially applied acetylcholine. Which of the following is the most likely mechanism of the toxin involved?
Options
- A.
It competitively binds to specific receptors on the postsynaptic membrane, blocking acetylcholine.
- B.
It cleaves specific proteins required for the fusion of synaptic vesicles with the presynaptic membrane.
- C.
It inhibits acetylcholinesterase in the synaptic cleft, preventing the breakdown of acetylcholine.
- D.
It blocks voltage-gated sodium channels on the motor end plate, preventing depolarization.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Neuromuscular Junction Signal|Neurotransmitter Receptor Specificity|Exocytosis
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse the mechanisms of different neuromuscular blockers.
The key diagnostic clue is the 'absence of ACh in the cleft' combined with a 'normal postsynaptic response' to exogenous ACh.
This perfectly isolates the failure to the presynaptic vesicle fusion machinery (exocytosis) rather than postsynaptic receptor antagonism.
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 |