Flashcards in Physiology Deck (28):
What substances are used to calculate GFR? Which is more accurate?
Inulin and creatinine. Inulin is more accurate.
What substance is used to calculate renal plasma flow (RPF)?
Para-aminohuppuric acid (PAH)
Describe the filtration of PAH.
PAH completely filtered at the nephron: freely filtered at the glomerulus (~20%) and the rest is secreted into the tubules (~80%). Thus the urinary excretion of PAH = RPF.
Describe the filtration of inulin.
Inulin is freely filtered at the glomerulus, and neither secreted nor absorbed at the tubules. Thus, it can be used to estimate GFR.
What is the volume of intracellular water in a 70 kg man? ECF?
28 L, 12 L
Volume of interstitial fluid in a 70 kg man?
Volume of plasma in a 70 kg man?
(urine conc/plasma conc) * urine flow rate
GFR = (w/ relation to inulin)
(Uinulin/Pinulin) * V
What does an increase in BUN indicate?
Decrease in GFR.
What is a normal BUN:creatinine ratio?
What does a BUN:creatinine ratio above 20:1 indicate?
Prerenal azotemia (not renal failure)
If both BUN and serum creatinine are increased at a ratio of 10:1, where is the problem?
Renal (kidney failure)
GFR = (w/ relation to glomerular pressures)
Kf [(Pgc-Pbs) - (πgc-πbs)
ERPF = (w/ regard to PAH)
(Upah/Ppah) * V
What is the effect of prostaglandins on GFR? RPF? FF?
GFR and RPF up
PGs' site of action on the glomerulus?
dilate afferent arteriole
Effect of NSAIDs on GFR? RPF? FF?
(FF is filtration fraction)
GFR and RPF down
Where is the site of action of Ang II on the glomerulus?
constricts efferent arteriole
Effects of Ang II on GFR? RPF? FF?
At what plasma concentration of glucose does some begin to appear in the urine?
At what plasma glucose concentraion are all renal tubular glucose transporters occupied (Tm)?
What kind of transporter reabsorbs glucose that is filtered into the Bowman's capsule? Where is this transporter located?
Na+/glucose cotransporter in the proximal tubule
Why must you alkalinize the urine to excrete more of an acidic substance such as sialycylic acid?
The unprotonated, charged form will not back-diffuse from urine into blood.
What are the 3 main Sx of pellagra?
Diarrhea, dermatitis, dementia
Diagram pathogenesis of Hartnup's disease.
deficient neutral aa transporter in proximal tubule -> Trp excreted in urine -> niacin (B3) can't be formed -> pellagra