Physiology Review I Flashcards
kidney autoregulation
myogenic and tubuloglomerular feedback
factors determining net filtration pressure
starling forces
nephrogenic diabetes insipidus
ADH receptors not functioning
-cannot increase reabsorption at CD
pt loses free water - develops hypernatremia
freely filtered material
Na, Cl, K, HCO3, urea, creatinine, AAs, inulin, PAH, insulin, myoglobin
not filtered at glomerulus
albumin and other plasma proteins, lipid soluble substances
filtration fraction
fraction of material entering kidney that is filtered - normally 20%
FF = GFR/RPF
RPF - renal plasma flow
sympathetics
vasoconstriction
-greater affect on afferent arteriole
increases filtration fraction
ANG II
vasoconstrictor on arterioles
efferent > afferent
preserve GFR in volume depleted state
NSAIDs in bleeding patient
inhibit prostaglandins - no vasodilation
-vasoconstriction to kidney - renal failure
Na/K ATPase
pumps 3 sodium out of tubule cell
pumps 2 potasisum into tubule cell
low sodium in cell - driving force - drive secondary transport of other substances
filtered load
rate at which substance enters nephron
= GFR x [P]
P free (unbound) concentration in plasma
excretion
= [U] x V
urine concentration x urine flow rate
net transport
= filtered load - excretion rate
= (GFR x [P]) - ([U] x V)
clearance
= excretion rate / plasma concentration
glucose reabsorption
saturable process
splay
rounding of reabsorption curve
-because some nephrons reach TM before others
PAH
saturable - transport maximum system
20% filtered ALWAYS (regardless of concentration)
-always clear the GFR filtered
as concentration increases - clearance decreases
excretion rate
= filtered load + secretion rate
inulin
filtered only
potassium, sodium, urea
filtered and SOME reabsorbed
glucose and bicarb
filtered and ALL reabsorbed
PAH
filtered and ALL secreted (at low concentrations)
low plasma concentration, clearance = renal plasma flow
creatinine
filtered and SOME secreted
inulin
gold standard for estimating GFR
-clearance independent of plasma concentration
intersection y-axis on clearance vs. plasma concentration
-GFR
creatinine
freely filtered and not reabsorbed (only small amount secreted)
creatinine production = creatinine excretion = filtered load of creatinine = Pcr x GFR
-clearance always greater than inulin (some always secreted)
glucose
low concentration - clearance = zero (all reabsorbed)
higher concentration - clearance reaches insulin
-never reaches it though, some always reabsorbed
highest to lowest clearance
PAH > creatinine > inulin > urea > sodium > glucose = albumin
it its in the renal vein
not cleared
free water clearance
how much water is being excreted
positive - hypotonic urine
negative - hypertonic urine
isotonic urine = urine osmolality of 300 mOsm/kg
C-H2O
= V - (Uosm x V) / Posm
urine osmolarity
plasma osmolatiry
V = urine flow rate
sodium
positive clearance
almost entire filtered load is reabsorbed
-clearance just above zero
aldosterone - increases sodium reabsorption - decreases its clearance
urea
freely filtered but partially reabsorbed
-floolws water
diuresis - increases urea clearance
antidiuresis - decreases urea clearance
ADH
increases reabsorption of urea in medullary CD
-increased BUN, decrease in clearance
small volume of concentrated urine
concentration of urea is high - but excretion not as high as in a diuresis (with much lower concentration)
