Homeostasis Flashcards
total body water is what percent
60% of wt.
The three major kidney functions
- ) Regulation of water and inorganic ions
- ) Removal of metabolic waste from the blood and their excretion in urine
- ) Removal of foreign chemicals from the blood and their excretion in urine
More fat = what effect on body water?
Less body water
What percent of body wt is intracellular fluid?
40%
Volume of unknown body fluid compartment = ?
quantity injected divided by final concentration
What kind of probe do you use to measure plasma volume?
l-albumin or evans blue dye
Plasma volume equals?
quantity of probe injected divided by plasma concentration of the probe. Blood volume can then be determined by dividing the plasma volume by 1- hematocrit
Extracellular fluid is composed of what?
Plasma and interstitial fluid
a good probe for ECF volume?
Inulin
How do you calculate ISF from ECF volume?
ECF- Plasma Volume
Probe for measuring total body water?
2H2O, 3H2O, Antipyrene
How do you determine ECF from TBW volume?
ECF = TBW- ECF
What factors determine fluid movement between plasma and ISF?
Starling forces: hydrostatic pressure and oncotic pressure
Oncotic pressure?
caused by proteins that cannot penetrate the capillary wall. For example, if protein conc goes up in plasma, then fluid will come in from ISF to correct osmotic balance.
Does plasma osmolarity play a role in fluid movement between ISF and plasma?
No…because the capillary wall is freely permeable to water and solute so these things are always in balance.
So what is the difference between osmotic pressure and oncotic pressure.
Oncotic pressure is a form of osmotic pressure. My understanding is that oncotic pressure refers to the pressure created by large non-permeable proteins in the blood making sure that the blood retains a certain fluid volume.
What regulates fluid movement between ICF and ECF?
OSMOSIS! Why?, because the plasma membrane is impermeable to most solutes. Therefore, a change in soulte concentration means a fluid shift must occur to keep things in homeostasis.
Plasma membrane permeable to urea?
yes
What is the difference between moles and osmoles?
Moles is a measure of molecules whereas osmoles is a measure of particles. You must differentiate because 1 mole can equal two osmoles and this has an effect on osmotic pressure created by that substnace.
osmolarity
amt of substance dissolved in a solution
What is osmotic pressure?
The pressure required to prevent osmosis. The amount of pressure that must be applied to prevent water from moving through the membrane
Osmotic pressure is directly proportional to the number of osmotically active solute (particles) in that solution
true…so osmotic pressure is directly proportional to osmolarity
Why is it important that the osmolarity be the same in different compartments
So that water is not moving into compartments rapidly
What occurs during a state of dehydration>
You will lose water from the ECF. Kidney function cannot be stopped thus ECF will slowly deplete. This causes an increase in osmolarity due to a high conc of solutes in teh Extracellular compartments. This inc in osmolarity draws water out from the cells. All fluid compartments lose volume and osmolarity is increased everywhere.
Normal osmolarity in all body compartments?
286mOsm
Osmolarity gap?
when measured plasma osmolarity is higher than the estimated plasma osmolarity. There is a missing osmotic particle.
