Increase alveolar ventilation decreases what?

Correct Answer: C

Rationale: Increased alveolar ventilation expels more CO₂, reducing blood PCO₂. Per the Henderson-Hasselbalch equation (pH = 6.1 + log([HCO₃⁻]/[0.03 × PCO₂])), lower PCO₂ increases pH (respiratory alkalosis) and decreases extracellular H⁺ concentration, as H⁺ binds with HCO₃⁻. Options A, B, and D misalign with this, making C correct.

Correct Answer: C

Rationale: During the resting (filling) stage of micturition, the detrusor muscle, a smooth muscle in the bladder wall, contracts minimally and stretches to accommodate urine (C), maintaining continence with sphincter tone. Urination (A) and sphincter relaxation (B) occur during voiding, and control (D) is broader, making C correct.

Correct Answer: D

Rationale: Mesangial cells contract to reduce filtration area (A), not produce systemic angiotensin II (B, a juxtaglomerular cell role), and phagocytose debris (C). A and C are true—contraction adjusts GFR, phagocytosis clears mesangium—while B is false, making D (A and C are correct) the answer.

Correct Answer: D

Rationale: Using Henderson-Hasselbalch: pH = 6.1 + log([HCO₃⁻]/(0.03 × pCO₂)), 7.60 = 6.1 + log([HCO₃⁻]/(0.03 × 40)). Solving: 1.5 = log([HCO₃⁻]/1.2), 10^1.5 = [HCO₃⁻]/1.2, 31.6 ≈ [HCO₃⁻]/1.2, [HCO₃⁻] ≈ 40 mEq/L. D (40) matches, indicating alkalosis.

Correct Answer: C

Rationale: Aldosterone (C) increases sodium reabsorption and potassium secretion in the distal tubule, regulating electrolytes. Renin (A) triggers the RAAS, angiotensin II (B) stimulates aldosterone, and angiotensin I (D) is a precursor, making C the direct effector.