Micturition Physiology — Flashcards

Flashcard 1: In an automatic bladder, emptying is _____voluntary

Answer: in

Flashcard 2: The _____ bladder is controlled by the intrinsic (intramural) plexus of the bladder.

Answer: Autonomous

Flashcard 3: _____ do not help create the medullary hyperosmolarity but prevent it from being dissipated.

Answer: Vasa recta

Flashcard 4: The _____ and outer medullary collecting ducts are permeable to H2O and impermeable to urea (ADH present)

Answer: cortical

Flashcard 5: The _____ bladder is controlled by the sacral reflex center of the bladder.

Answer: Automatic (Reflex) bladder

Flashcard 6: The amount of _____ excreted in the urine is directly proportional to muscle mass

Answer: creatinine

Flashcard 7: Renal autoregulation is primarily controlled by changing _____ of the afferent arteriole

Answer: vascular resistance

Flashcard 8: The _____ mechanism of renal autoregulation states that renal afferent arterioles contract in response to vasoactive substances released by the macula densa

Answer: tubuloglomerular feedback

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).