NEETZoologyExcretory Products and their Elimination
A patient experiences a significant fall in Glomerular Filtration Rate (GFR) and blood volume, which activates the juxtaglomerular (JG) cells to release renin. This cascade eventually leads to the secretion of a steroid hormone from the adrenal cortex. What will be the primary effect of this steroid hormone on the renal tubules?
Options
- AStimulation of the reabsorption of Na ⁺ and water, and excretion of K ⁺ and phosphate ions
- BIncreased secretion of Na ⁺ and water into the filtrate to maintain osmolarity
- CDecreased reabsorption of water from the distal tubules due to the suppression of ADH release
- DStimulation of maximum reabsorption of electrolytes and water in the proximal convoluted tubule (PCT)
Correct answer
A. Stimulation of the reabsorption of Na ⁺ and water, and excretion of K ⁺ and phosphate ions
Step-by-step solution
A fall in GFR and blood volume activates the Renin-Angiotensin-Aldosterone System (RAAS). Renin converts angiotensinogen to angiotensin I, which is further converted to angiotensin II. Angiotensin II stimulates the adrenal cortex to release aldosterone, a steroid hormone. According to NCERT, aldosterone acts mainly at the renal tubules (specifically the distal parts) and stimulates the reabsorption of Na ⁺ and water, and the excretion of K ⁺ and phosphate ions. Option 2 is incorrect as aldosterone promotes reabsorp