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29 Cards in this Set
- Front
- Back
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3 fluid compartments of the body
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ECF (plasma & ISF)
ICF TBW |
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percent of body weight equal to water
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60% (TBW)
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percent of TBW in ICF
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40%
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percent of TBW in ECF
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20%
- plasma = 4% - ISF = 16% |
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characteristics of ICF
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high K, low Na & Cl (b/c pump)
little affect from change in Na |
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characteristics of ECF
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high Na, low K
Na & water move freely proteins do not increase in water goes here first changes in Na affect ECF first |
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changes in Na concentration affect...
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ECF volume (compartment size)
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concentration of Na in body
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58 meq/Kg body weight
135-145 mM in ECF |
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normal osmolarity in body
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290 mOSM
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measure TBW
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labeled water
long time to equilibrate not used in clinic |
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measure ECF
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infuse LOW CONC innulin or mannitol
(higher conc will cause vol shift) |
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measure plasma fluid volume
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use labeled proteins
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measure ICF
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can't measure directly
diff between TBW & ECF |
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measure ISF
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can't measure directly
diff between ECW & plasma volume |
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changes in water affect...
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total body osmolarity
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hyperosmotic expansion leads to
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increased plasma osmolarity, plasma Na & EC volume
decreases IC volume increase urine Na (triggers compensatory mechs-water back in to cell) |
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Isoosmotic expansion leads to
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expansion of ECF volume but not ICF
plasma os, plasma Na & IC volume remain the same EC increases increase urine Na |
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hypotonic expansion leads to
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decreased plasma os & plasma Na
increased EC & IC increase in urine Na (triggers ionic mvt out of cell) |
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osmotic pressure
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osmotic difference between compartments
depends on membrane characteristics & starling |
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estimate plasma osmolarity
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Posm = (2xPNa) + [glucose]/18 + BUN/3
or 2xPNa |
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calculate dilution
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V=Q/C
volume=quantity/concentration |
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sensing & response to volume changes
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Baroreceptors: activate symp & RAS decrease Na excretion
increase ECFV Osmoreceptor: activate ADH, decrease H2O out, increase ECFV w/decreased Posm Atrial Stretch: activate ANP, increase Na out, decrease ECFV |
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Affect of diarrhea on body fluids
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isotonic fluid loss
little effect on ICF or serum Na |
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Affect of sweating on body fluids
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hypoosmotic water loss
like diarrhea BUT also affects ICF & Serum Na |
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Affect of ADH on body fluids
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hypotonic volume expansion
(opposite of diarrhea) ICF expansion |
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synthesis in the kidney
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Epo
Renin 1,25 Vit D |
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Affect of adrenal insufficiency on body fluids
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loss of Na
ICF expands TBW, ECF vol & Osm, & Serum Na decrease |
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factors affecting body fluid composition
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Diarrhea- isotonic depletion
Sweating- hypotonic depletion ADH- hypotonic expansion Adrenal Insuff- Hypertonic depletion |
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Regulation of Extracellular fluid volume
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Baroreceptors
-activate Symp & RAS -affect Na excretion Osmoreceptors -sense plasma osmolality -activate ADH -affect water excretion Atrial stretch -sense ECF volume -affect Na excretion |
