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Question #45730
The Question
A patient with a traumatic brain injury exhibits continuous diuresis with highly dilute urine, despite elevated blood osmolarity. An MRI reveals intact hypothalamic nuclei but severed axonal tracts in the infundibulum (pituitary stalk). Which of the following statements correctly describes the physiological disruption causing this condition?
Options
- A.
The synthesis of vasopressin in the pars nervosa is halted, preventing facultative water reabsorption in the collecting duct.
- B.
Action potentials from osmoreceptors fail to reach the neurohypophysis, preventing the calcium-dependent exocytosis of stored ADH.
- C.
The hypophyseal portal circulation is disrupted, preventing hypothalamic releasing hormones from triggering ADH secretion.
- D.
The threshold for osmoreceptor activation is abnormally elevated, leading to a failure in the synthesis of aquaporin channels in the descending limb of loop of Henle.
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
Osmoreceptors|Hypothalamic neurons|Exocytosis
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse the regulatory mechanisms of the anterior and posterior pituitary.
The trap in Option C tests the misconception that ADH release is mediated by releasing hormones via the portal system.
Option A tests the location of ADH synthesis (Hypothalamus vs Pars Nervosa).
The correct answer (B) requires synthesizing the concept of neural conduction (action potentials) with endocrine release (exocytosis of ADH) to explain Central Diabetes Insipidus.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Excretory Products and Their Elimination - Class 11 |
| Concept | ADH (Vasopressin) Logic |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |