The distal portions of the tubules are relatively impermeable to

Correct Answer: C

Rationale: Distal tubules are impermeable to renin it's a hormone, not reabsorbed (e.g., acts systemically). Aldosterone affects Na cells respond. ADH adjusts water collecting duct permeable. Macula densa is a structure not a substance. Renin's impermeability distinguishes it, key to its systemic role, unlike hormones affecting tubules.

Correct Answer: B

Rationale: Kidney innervation (sympathetic) regulates arteriole diameter e.g., constricts afferent/efferent, adjusts GFR. Filtrate composition is glomerular not neural. Water reabsorption is hormonal (ADH) not innervation. Brush border is structural not regulated. Arteriolar control distinguishes it, key to blood flow, unlike filtrate or tubular functions.

Correct Answer: B

Rationale: Aldosterone is secreted by zona glomerulosa e.g., adrenal cortex, boosts Na reabsorption. Adjacent to macula densa is JGA not aldosterone. Tube is ureter unrelated. Hypothalamus synthesizes ADH not aldosterone. Adrenal origin distinguishes it, key to its role, unlike JGA or hypothalamic errors.

Correct Answer: A

Rationale: Renin is secreted by JG cells e.g., JGA responds to low BP. Ureter transports not secretes. Hypothalamus makes ADH not renin. Micturition is urination unrelated. JG secretion distinguishes it, key to BP regulation, unlike tubes or actions.