MCAT® ExamBiological and Biochemical Foundations of Living SystemsMedium
A patient with severe renal failure exhibits an inability to properly regulate their blood pressure, often experiencing episodes of both hypertension and hypotension. This dysregulation is most likely due to the impaired function of which of the following endocrine systems?
- AInsulin-glucagon regulation
- BGrowth hormone pathway
- CRenin-angiotensin-aldosterone system (RAAS)
- DThyroid hormone axis
Show answer & explanationAnswer & explanation
Correct answer: C. Renin-angiotensin-aldosterone system (RAAS)
The kidneys play a central role in the Renin-Angiotensin-Aldosterone System (RAAS), which is a key regulator of blood pressure and fluid balance. Impaired kidney function directly disrupts RAAS, leading to blood pressure dysregulation.
Why the other options are wrong
- A. Insulin and glucagon regulate blood glucose levels, not blood pressure.
- B. Growth hormone primarily regulates growth and metabolism, with no direct role in acute blood pressure regulation.
- D. Thyroid hormones primarily regulate metabolism and growth, not direct blood pressure control.
Renin-Angiotensin-Aldosterone System (RAAS)
A hormone system that regulates blood pressure and fluid balance. It is initiated by the kidneys' release of renin in response to low blood pressure or fluid volume.
- Renin converts angiotensinogen to angiotensin I.
- ACE converts angiotensin I to angiotensin II (a potent vasoconstrictor).
- Angiotensin II stimulates aldosterone release, increasing Na+ and water reabsorption.
Memory trick: RAAS 'R'aises 'A'nd 'A'djusts 'S'ystemic pressure.