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Question #47396
The Question
During an emergency, the adrenal medulla releases catecholamines that activate the cAMP secondary messenger cascade, leading to bronchodilation. However, in a patient suffering from severe ankylosing spondylitis (fusion of the costovertebral joints), this sympathetic response fails to significantly increase pulmonary ventilation. Which of the following best explains this physiological limitation?
Options
- A.
The rigid thoracic architecture restricts the dorso-ventral expansion of the rib cage, preventing the generation of adequate negative intra-pulmonary pressure.
- B.
The sympathetic nervous system relies on the IP3/Ca2+ pathway, rather than the cAMP cascade, to relax bronchial smooth muscles.
- C.
The fusion of the ribs directly inhibits the phrenic nerve, preventing the antero-posterior expansion of the thoracic cavity by the diaphragm.
- D.
Catecholamines paradoxically induce bronchoconstriction in restrictive lung disorders by acting on alpha-adrenergic receptors.
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
Epinephrine|Beta2_Adrenergic_Receptors|Bronchodilation|Rib_Cage_Dynamics
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Decoupling airway resistance (obstructive factors) from thoracic compliance (restrictive factors).
Students often assume chemical bronchodilation universally improves ventilation, failing to realize that Boyle's Law dictates volume expansion must occur first to create the negative pressure gradient required for inspiration.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Locomotion and Movement - Class 11 |
| Concept | Rib Cage Architecture |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |