05.05 - Homeostasis (Rao) - Lecture, no reading Flashcards
Formula for Plasma Osmolarity
(2 x Na mM) + (Glucose mOsm) + (Urea mOsm)
Major cation in ICF
K+
What happens to normal RBC when placed in solution of Low Pna and High Glycerol
Initially shrinks, then swells
Probes for Total Body Water
2H2O, 3H2O, Antipyrene
Major extracellular anion
Cl-
Is Cl- greater in plasma or interstitial fluid
Greater in interstitial fluid (Gibbs Donnan Effect)
Formula for BV
BV= PV/(1-Hct)
Probe for measuring ECFV
Inulin, Thiosulfate, Na+
Major cation in ECF
Na+
Is HCO3- greater in ICV or ECV
ECV
Is PO4+ greater in ICV or ECV
ICV
How does Infusion of Isotonic Salt Solution change ECF and ICF
Increase ECF, no change in ICF
Formula for ICF
ICF = TBW - ECF
Is SO4+ greater in ICV or ECV
ICV
Permeability of Na, Urea, Water, Glycerol across PM
Im, Per, Per, Slowly permeable
What causes Gibbs Donnan Effect?
Proteins impermeable to PM - Anionic so bind Na in plasma and repel Cl- into interstitial fluid
Is Cl greater in ICV or ECV
ECV
How do you correct for filtration/excretion in calculating ECF
Subtract excreted value from numerator
Ca2+ in ICF vs ECF
None in ICF
Is Na greater in plasma or interstitial fluid
Plasma (Gibbs Donnan Effect)
Formula for ISF (interstitial)
ISF = ECF - PV
What percent of Blood is plasma vs rbc
60% plasma, 40% rbc
If probe is metabolized, will it over or underestimate the volume
Overestimate
What to look for when elevated Osmolarity Gap
Missing Osmotic particle
2 Major anions in ECF
Cl-, HCO3
3 Major anions in ICF
Protein, Bicarb, Phosphate
If probe is synthesized, will it overestimate or underestimate volume?
Underestimate
What Osmolarity gap is abnormal
>10
What percent of water intake is from food + drink
88%
Is Mg greater in ICV or ECV
ICV
What percent of TBW is BV
8%
Formula for PV with probe
PV = Q / Conc.
Why is Inulin good probe for ECFV
Smaller than Albumin, can diffuse across capilary wall but not PM
Probe for measuring PV
131 I-Albumin, Evans blue dye
