It is the intrinsic capability of blood vessels to constrict when blood pressure is increased?

Correct Answer: C

Rationale: The myogenic mechanism is vessels' intrinsic constriction to high pressure autoregulates GFR (e.g., afferent stretch). Hormonal control (e.g., angiotensin) is extrinsic renin-driven. Sympathetic control uses nerves reduces GFR. Tubuloglomerular feedback is macula densa NaCl-based. Intrinsic response distinguishes it, key to vascular autoregulation, unlike extrinsic or feedback controls.

Correct Answer: B

Rationale: Intracellular potassium is ~150 mM high vs. extracellular ~4 mM (e.g., Na /K -ATPase maintains). 125 mM is close understated. 3.5 mM is extracellular opposite. 50 mM underestimates gradient incorrect. High concentration distinguishes it, critical for membrane potential, unlike lower values.

Correct Answer: D

Rationale: Na absorption in ascending Loop is active in thick (Na /K /2Cl⁻ cotransport) and passive in thin (e.g., gradient-driven). All passive ignores thick's pump false. All active overstates thin incorrect. Reversed activity misaligns thick is active. Dual mechanism distinguishes it, critical for concentration gradient, unlike uniform or swapped errors.

Correct Answer: D

Rationale: Normal adult blood pH is 7.35-7.45 tightly regulated (e.g., bicarbonate buffer). 7.45-7.8 is alkalosis abnormal. 6.8-7.35 includes acidosis too broad. 6.8-6.8 is lethal false. Narrow range distinguishes it, critical for homeostasis, unlike wide or extreme ranges.

Correct Answer: C

Rationale: H binds HCO₃⁻ first forms H₂CO₃, then splits to CO₂/H₂O (e.g., buffering sequence). H₂CO₃ to CO₂ is second not initial. HCO₃⁻ to H₂CO₃ reverses H drives. All in order missequences false. Binding start distinguishes it, critical for buffer mechanics, unlike subsequent or reversed steps.