First stimulation in the micturition reflex is when the volume reaches?

Correct Answer: A

Rationale: First micturition reflex stimulation is at 150 mL initial urge from stretch (e.g., afferent signal). 300 mL is fullness later. 400 mL discomfort escalated. 560 mL exceeds typical late. Early trigger distinguishes it, critical for reflex onset, unlike higher volumes.

Correct Answer: B

Rationale: The thin descending limb is water-permeable, ion-impermeable osmosis concentrates filtrate (e.g., countercurrent). PCT is leaky ions/water pass. Cortical collecting duct adjusts with ADH ions move. Thick ascending pumps ions water-impermeable. Unique permeability distinguishes thin descending, critical for gradient, unlike leaky or adjustable segments.

Correct Answer: C

Rationale: ADH won't stop diuresis in nephrogenic diabetes insipidus tubules resist (e.g., receptor defect). Lack of ADH responds diabetes insipidus. Excess water dilutes ADH corrects. Combined is treatable ADH works. Resistance distinguishes it, critical for ADH failure, unlike responsive causes.

Correct Answer: B

Rationale: Low [H₂CO₃] is difficult to measure rapidly dissociates to CO₂/H₂O (e.g., lab challenge). Easy estimation misstates requires CO₂ proxy. Ineffective ignores Henderson-Hasselbalch false. Replacement isn't needed CO₂ suffices. Measurement difficulty distinguishes it, critical for pH calculation, unlike estimation or equation errors.

Correct Answer: A

Rationale: The urinary system excretes waste (e.g., urea) and balances fluids/electrolytes not enzyme production (digestive), oxygen transport (respiratory), or temperature (skin). This defines its primary role, critical for homeostasis, contrasting with unrelated systems.