Basic Physiological Principles Flashcards
mMol/L
How many molecules of substance/L. (mg/mw)/L
mEq/L
Ionic charge
mMol/L * Valence * number of ions in molecule
Ca has 1 ion in CaCl2
mOsm/L
mMol/L * total # of particles in molecule
CaCl2 has 3 particles
% Solution
Amount of a substance in g per 100mL solvent.
% Solution Saline
0.9% Na
Total Body Fluid in L, how is it divided up?
40 L. 25 in cells, 15 EC, 5 in vasculature
Concentration of sodium EC and in skeletal muscle
~140 mEq/L EC, ~10 mEq/L
Concentration of K EC and in skeletal muscle
~4 mEq/L EC, ~145 mEq/L IC
Counter ion for HCO3-
IC proteins, which are negatively charged at physiological pH.
How does the body deal with osmotic imbalance?
Moves water to equilibrate rapidly.
Daily loss of water due to urine
Decreases with exercise and hot weather. Designed to account for loss via other routes.
Loss of water in feces
Remains relatively constant.
Two characteristics of osmotic particles
Must be dissolved and contained by semipermeable membrane.
Does sodium contribute to osmotic pressure of capillaries?
No, because it can pass through, but it does contribute with cell membranes.
Is a 10 mOsm/L difference big or small?
Big, 1 mOsm is 19.3 mmHg.
Solutes that stay extracellular
NaCl, NaHCO3, large sugars
Solutes that go intracellular
K, small sugars (glucose)
What happens when normal saline is infused?
Isotonic solution, 0.9% NaCl, which will stay EC. Goes from vasculature to interstitium, not taken up. Water distributes with the salt. Does not change the osmolarity of the solution.
What happens with high NaCl intake?
Salt into GI tract, rapidly taken into bloodstream, distributes to extracellular volume, does not go IC. Concentration of EC fluid increases. Driving force pulls water out to cells to decrease the concentration in EC space. Osmotic concentration in cells subsequently increases.
What happens when volume is lost due to diarrhea?
GI secretions (with the exception of the mouth) are isotonic. Volume contraction occurs, but there is no ionic composition change. Fluid comes from EC space. No driving force, no loss of IC volume.
Paracellular Transport
Between cells, through tight junctions.
Transcellular Transport
Through cells, dictated by the population of apical protein transporters and basolateral protein transporters.
How is water transported through epithelial cells?
Aquaporins.
Solvent drag
Driving force for water movement, anything dissolved in it will get pulled. RBC’s included.
