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Question #47405
The Question
A patient is completely unable to perform the rotational movement of the head (the 'No' gesture), despite having a structurally flawless articulation between the atlas and axis vertebrae. Electrophysiological tests reveal that action potentials successfully reach the motor nerve terminals innervating the associated neck muscles, but no action potential is generated across the sarcolemma. Which of the following physiological failures directly explains this condition?
Options
- A.
Inhibition of voltage-gated Ca2+ channels at the axon terminal, preventing the exocytosis of acetylcholine.
- B.
Failure of Ca2+ ions to bind with the troponin subunit in the sarcoplasm, keeping the myosin-binding sites masked.
- C.
Degeneration of the synovial membrane in the condyloid joint between the occipital condyles and the atlas.
- D.
Inability of the motor endplate to reach the threshold potential due to a massive efflux of K+ ions from the sarcoplasmic reticulum.
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
Synovial_Joint_Varieties|Action_Potential_Threshold_Logic|Synaptic_Vesicle_Exocytosis_Trigger
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Integrating skeletal anatomy (atlas-axis pivot joint) with the strict sequential electrophysiology of the neuromuscular junction.
The trap relies on Process Sequence and Location Specificity.
Students often reflexively associate 'muscle failure' with Troponin-Calcium binding (Option B), failing to note the specific diagnostic clue that the signal transduction failed prior to the sarcolemma's depolarization.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Locomotion and Movement - Class 11 |
| Concept | Synovial Joint Varieties |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |