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Test: MCAT Biology
The interaction between blood pressure and kidney function in humans requires coordination by the renin-angiotensin-aldosterone system (RAAS). This system involves the dynamic interplay of the kidneys, lungs, and blood vessels to carefully regulate sodium and water balance.
A normal human kidney has cells adjacent to the glomerulus called juxtaglomerular cells. These cells sense sodium content in urine of the distal convoluted tubule, releasing renin in response to a low level. Renin is an enzyme that converts angiotensinogen to angiotensin I (AI). AI is converted to angiotensin II (AII) by angiotensin converting enzyme (ACE) in the lung.
AII stimulates aldosterone secretion in the zona glomerulosa of the adrenal gland. Aldosterone then acts to upregulate the sodium-potassium pump on the basolateral side of distal tubule epithelial cells to increase sodium reabsorption from the urine, as well as increasing potassium excretion.
1. | A scientist is studying the effect of aldosterone on the distal tubule cells of a kidney. He finds that antidiuretic hormone also exerts changes on the concentration of urine produced by this kidney. Where does antidiuretic hormone exert its most potent effect? |
Thick ascending loop of Henle
Glomerulus
Collecting duct
Proximal tubule
Distal tubule
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