Integrative Responses to Fluid Challenges — Flashcards

Flashcard 1: Vasopressin escape in SIADH results due to downregulation of _____ production.

Answer: aquaporin 2

Flashcard 2: Renal blood flow (RBF) remains relatively constant between mean arterial pressure (MAP) ranges of _____ to 180 mmHg

Answer: 80

Flashcard 3: PCT cells are involved in sustaining _____ which increases solute and water reabsorption in response to increased GFR.

Answer: glomerulotubular balance

Flashcard 4: A _____ shift in renal pressure natriuresis curve is caused by angiotensin II by increasing Na and water retention

Answer: rightward

Flashcard 5: What is the feedback gain associated with blood volume control of kidney?_____

Answer: Infinity

Flashcard 6: Decreases in _____ (e.g. hemorrhage or decreased Na+) cause a decrease in renal perfusion pressure, which in turn increases secretion of the enzyme renin

Answer: ECF volume

Flashcard 7: In the absence of _____, the principal cells of the late distal tubule and collecting duct are impermeable to water

Answer: ADH

Flashcard 8: The central action of angiotensin II includes increased _____ secretion and induction of thirst

Answer: ADH

Flashcard 9: What is the formula for renal clearance ($C_x$)?

Answer: $C_x = \frac{U_x V}{P_x}$

Extra: $U_x$ = Urine concentration of X $P_x$ = Plasma concentration of X $V$ = Urine flow rate

Flashcard 10: What equation is used to calculate **free-water clearance** ($C_{H_2O}$)?

Answer: $$C_{H_2O} = V - C_{osm}$$ (where $V$ = urine flow rate; $C_{osm}$ = osmolar clearance)

Extra: Free-water clearance ($C_{H_2O}$) represents the volume of solute-free water that must be added to or removed from the urine to make it isotonic with plasma. - If **$C_{H_2O} = 0$**: Urine is isosthenuric (isosmotic to plasma). - If **$C_{H_2O} > 0$**: Free water is excreted (dilute urine; $U_{osm} < P_{osm}$). Seen in low ADH states (e.g., diabetes insipidus, water intoxication). - If **$C_{H_2O} < 0$**: Free water is reabsorbed (concentrated urine; $U_{osm} > P_{osm}$). Seen in high ADH states (e.g., SIADH, dehydration).