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Question #46342
The Question
During the expulsion phase of parturition, a mother performs forced expiration against a closed glottis, actively recruiting her diaphragm and abdominal muscles. Despite this intense voluntary somatic effort, labor is prolonged due to a failure in the primary neuroendocrine reflex. Which of the following best explains the physiological disconnect occurring in this scenario?
Options
- A.
Impairment of the fetal ejection reflex halts the positive feedback loop of maternal oxytocin, depriving the voluntary diaphragmatic effort of its essential involuntary myometrial synergy.
- B.
Downregulation of oxytocin receptors on the skeletal muscles of the diaphragm prevents their synchronized contraction with the uterine myometrium.
- C.
A premature drop in maternal progesterone levels inhibits the Fergusson reflex, directly paralyzing the voluntary abdominal musculature.
- D.
Inadequate secretion of relaxin from the maternal posterior pituitary prevents the widening of the birth canal, negating the increased intra-abdominal pressure.
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
Diaphragm|Parturition_Neuroendocrine_Reflex|Oxytocin|Abdominal_Muscles
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between the involuntary neuroendocrine-driven smooth muscle contractions (myometrium via oxytocin) and the voluntary somatic muscle exertion (diaphragm/abdomen).
The trap relies on functional and anatomical confusion—students often misattribute the target tissues of oxytocin (assuming it acts on the diaphragm during labor) or misidentify the source of relaxin (confusing it with posterior pituitary hormones like oxytocin).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Breathing and Exchange of Gases - Class 11 |
| Concept | Diaphragm Mechanics |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |