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Question #45776
The Question
Calcium ions (Ca2+) serve as the critical systemic node linking motor neuron signal transduction to the sliding filament mechanism. Which of the following statements regarding this integrated pathway is INCORRECT?
Options
- A.
Depolarization of the pre-synaptic membrane opens voltage-gated Ca2+ channels, causing an influx of Ca2+ that triggers the exocytosis of acetylcholine into the synaptic cleft.
- B.
Blocking voltage-gated Ca2+ channels at the axon terminal prevents downstream muscle contraction, even if the sarcoplasmic reticulum possesses normal Ca2+ reserves.
- C.
Upon release into the sarcoplasm, Ca2+ binds to a specific subunit of tropomyosin, inducing a conformational change that pulls troponin away from the myosin-binding sites on F-actin.
- D.
The release of Ca2+ from the sarcoplasmic reticulum into the sarcoplasm is an intracellular event triggered by the propagation of an action potential deep into the muscle fiber via T-tubules.
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
Secondary_Messenger_Cascade|Synaptic_Vesicle_Exocytosis_Trigger|Calcium_Signaling
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: The structural and functional distinction between the regulatory proteins Troponin and Tropomyosin.
Students frequently confuse which protein acts as the Ca2+ sensor (Troponin) versus which protein physically masks the binding site (Tropomyosin).
The question also tests the dual, location-specific roles of Ca2+ (extracellular influx for neural exocytosis vs. intracellular release for muscular contraction), forcing the student to navigate systemic physiological dependencies.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Locomotion and Movement - Class 11 |
| Concept | Muscle Type Differentiation |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |