Answer: A fall in blood pressure or renal blood flow, triggering renin release.
- A A drop in blood calcium detected by the parathyroid-linked pathway
- B A rise in blood glucose that is sensed directly by the kidney
- C Excess ADH circulating in the blood reaching the kidney
- D A fall in blood pressure or renal blood flow, triggering renin release
Correct answer: D. A fall in blood pressure or renal blood flow, triggering renin release
Explanation: Falling blood pressure/renal perfusion stimulates juxtaglomerular cells to release renin, which converts angiotensinogen to angiotensin I, eventually raising aldosterone and restoring blood pressure.
The hypothalamus releases hormones that direct the pituitary, which releases its own trophic hormone to a target gland; that gland's hormone output then feeds back (dashed lines) to suppress both the pituitary and hypothalamus once levels are sufficient - a self-correcting loop running the entire endocrine system.
Concept context
The endocrine glands, hormone classification and mechanism of action, and negative feedback regulation.