Concentration/Dilution (lec 12) Flashcards
Normal urine is what-tonic?
Its normal osmolarity is?
hypertonic
285-295
Kidney response to HYPOsmotic body fluid?
excretes dilute urine (water diuresis)
hyposmotic = water excess
Kidney response to HYPERosmotic fluid?
excretes concentrated urine (antidiuresis)
hyperosmotic = water deficit
Kidney’s ability to regulate water excretion is dependent or independent of solute excretion?
independent
NaCl transport in descending LOH?
no active transport,
highly permeable to H2O
NaCl transport in ascending LOH?
active transport of NaCl back to blood (reab),
impermeable to water
Osmotic gradient in interstitial space (cortex to medulla) has what relationship with urine in collecting ducts?
it removes H2O from urine
As fluid flows down descending LOH, what happens to the concentration?
becomes more [ ]
water is pulled from fluid
As fluid flows up descending LOH, what happens to the concentration?
becomes diluted
NaCl is pulled from fluid
Largest osmotic gradient possible across ascending LOH?
200
Back diffusion = ?
active ion transport out of lumen
Countercurrent Multiplier does?
creates large overall gradient from LOH (corticomedulla border to tip of papilla)
Beginning osmolarity of fluid as enters Descending LOH?
300
Countercurrent Multiplier: Thick Ascending Limb of LOH
NaCl transport mechanism?
Na+/K+/2Cl− cotransporter pulls NaCl from lumen into tubule cell
K+/Cl- cotrans and Na+/K+ pump move NaCl into medulla ISF
Ascending limb IMPERMEABLE to H2O, H2O can’t follow Na+
Countercurrent Multiplier: Thick Ascending Limb of LOH
NaCl transport results in?
ISF osmolarity ↑ to 400,
ascending limb osmolarity ↓ to 200
Countercurrent Multiplier: Descending Limb of LOH
H2O transport mechanism?
Fluid entering descending limb has 300 Osm,
ISF is now 400 Osm (from ascending transport of NaCl),
H2O pulled from lumen into ISF
Coutercurrent Multiplier: Descending Limb of LOH
H2O transport results in?
descending limb osmolarity ↑ and is pushed down the limb,
fluid Osm keeps ↑ as it approaches distal turn of tube
Main drive of the countercurrent multiplier is?
active transport
Vasa Recta is?
capillary that follows inside the LOH hairpin turn
Vasa Recta purpose?
preserve the ISF gradient created by LOH
Vasa Recta: Descending Loop mechanism?
passive diffusion of NaCl in and H2O out
Vasa Recta: Ascending Loop mechanism?
passive diffusion of H2O out and NaCl in
Urea is made by?
hepatic protein catabolism
Urea is recycled where in the kidney?
medulla
Urea recycling is ↑ by?
ADH
AHD affects Urea permeability how/where?
↑ urea permeability in the INNER medullary collecting ducts
Early DCT: NaCl transportation mechanism?
NaCl cotransport and Na+ channel
from lumen into cell
Na+/K+ pump and Cl- channel
move NaCl into ISF
Early DCT: NaCl cotransport blocked by what?
thiazide diuretics
Early DCT: Impermeable to what?
Results in?
H2O
continued dilution of tubular fluid,
fluid remains HYPOsmotic
Late DCT: Na+ and K+ transport mechanisms
Basolateral membrane?
Na+/K+ATPase -> Na+ reabsorption/K+ secretion
Late DCT: Na+ and K+ transport mechanisms
Apical membrane?
Na+ and K+ channels
Late DCT: Principle cells purpose?
Controlled by?
reab Na+/secrete K+
Aldosterone
Late DCT: Aldosterone affects Principle Cells how?
↑ # of apical Na+ channels,
↑ Na+/K+ATPase
Late DCT: ⍺-Intercalated cells purpose?
Mechanism?
secrete H+/reab K+ (balance pH)
H+ATPase
H+/K+ATPase
Collecting Duct (CD): Permeable to?
ONLY in presence of?
H2O, Urea
ADH (vasopressin)
Collecting Duct: ADH mechanism to cause H2O permeability?
ADH binds baso memb of DCT or CD cells ->
activates cAMP ->
↑ aquaporins (water channels) in apical membrane
