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Question #45787
The Question
The mechanism of calcium mobilization and subsequent muscle contraction varies significantly between skeletal and smooth muscles. Which of the following statements is INCORRECT regarding these physiological pathways?
Options
- A.
In skeletal muscles, acetylcholine-induced depolarization of the sarcolemma triggers Ca2+ release from the sarcoplasmic reticulum without the involvement of IP3.
- B.
In smooth muscles, hormones such as adrenaline can trigger Ca2+ release from the sarcoplasmic reticulum via G-protein coupled receptors and secondary messengers.
- C.
During the 'fight or flight' response, adrenaline directly initiates the sliding filament mechanism in skeletal muscles by activating sarcolemmal GPCRs.
- D.
The Ca2+ mobilized in smooth muscles binds to calmodulin rather than troponin, leading to the phosphorylation of myosin heads via Myosin Light Chain Kinase.
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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
Hormone_Receptors_Location|Feedback_Mechanism_Loops|Cyclic_AMP
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse the systemic effects of adrenaline ('fight or flight') with the direct initiation of skeletal muscle contraction.
Because skeletal muscles are highly active during an adrenaline rush, students falsely assume adrenaline directly triggers their contraction.
However, skeletal muscle contraction remains strictly under voluntary somatic neural control (ACh), while adrenaline only modulates their metabolism (glycogenolysis) and directly affects smooth/cardiac muscle contraction via secondary messengers.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Locomotion and Movement - Class 11 |
| Concept | Sliding Filament Theory Mechanics |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |