Jan4 M1-Water balance Flashcards
ref phgy individual weight and body water
70kg. 60%. 42L
how much fluid goes IV if give 1L water in IV compartment
83ml. 1/12
body fluid compartments and values
IC: 8/12
IS: 3/12
IV: 1/12
daily water intake and output value
2550 mL
daily urine output and insensible losses
1500 mL urine. 900 mL insensible losses
water in the PCT
(67%) NaK ATPase drives Na movement. Water follows (tight junctions and aquaporins)
normal ECF osmolality (or osmolarity same thing)
275-290 mOsm/kg
osmolality equation (blood)
Nax2 + urea + glucose = 275-290
urea and alcohol osmotically active or inactive + def of that
urea: inactive (crosses cell membrane)
alcohol: active. add to equation if present
ADH type of hormone + produced where and released where
peptide. group of hypothalamic neurons. released from posterior pituitary
ADH acts how (exact names of receptors and proteins)
binds to V2 receptors in the collecting duct to stimulate the insertion of aquaporin-2 channels in the luminal membrane
2 stimuli to ADH release and sensed where
hypertonicity, sensed by osmoreceptors in the hypothalamus
hypovolemia, sensed by carotid sinus. signals hypothalamus
osmolality threshold for ADH release
290 or more
how much water reabso at CD when no ADH and consequence
none. water diuresis. CD is impermeable to water
diabetes insipidus pathophgy
malfunction of ADH system. ADH not released or doesn’t bind receptor. urine high in water
DI can happen when
head injury or post neuro procedure
2 main components of water regulation
permability to CD to water via ADH
high osm of medullary interstitium
osmolality of the filtrate in Bowman’s space
same as blood (275-290)
what nephrons do the high osm in the medullary interstitium and % they represent
juxtamedullary glomeruli (or corpuscules)
% of juxtamedullary glomeruli vs not and loop of Henle in each
20% juxtamedullary: loop of Henle is in medulla + vasa recta with it
80% short loop of Henle and is in the cortex
max urine osms
1400
osms in diff parts of the nephron when ADH active vs when inactive
PCT: 300 DL: 600 to 1200 AL: 1200 to 100 DCT: 100 CT and CD: 300 to 1200. if no ADH, osm of 50 in CT and CD.
tDL and TAL: what they are permeable to (most importantly)
tDL: water and not salt
TAL: salt and not water
filtrate osms as enters DCT
100 mosm/L
how filtrate osms goes from 1200 to 100 in AL
Na-Cl cotransporters pull Na and Cl into interstitium
function of vasa recta and why the shape
take extra water and solutes back in the blood
shape avoids losses of solute gradient from interstitium
2 portions of vasa recta and osms in them
descending limb of vasa recta: 300 to 1200
ascending limb of vasa recta: 1200 to 300
vasa recta: what is the net reabsorption
only the water and solute net abso by the medullary tubules
water reabso in %
67% PCT
15% tDL
0% in TAL and DCT
ADH for the rest in CT (CCD) and CD (MCD)
furosemide site of action
inhibits Na-K-2Cl cotransporter in TAL by binding Cl site
medullary interstitium and urine osmolality in patients on furosemide
300
osms in different parts of the nephrons when on furosemide with ADH and without ADH
with and without ADH: 300 in all tubules
why osms don’t increase in tDL when on furosemide
no osmotic gradient to pull water in interstitium
