K1 - Body Fluid Compartments and Challenges to Homeostasis Flashcards
what is osmolarity ?
concentration in a solution of osmotically active particles
How can osmolarity be calculated?
molar concentration x number of osmotically active particles
what is the difference between osmolarity and osmolality?
osmolality is measures in osmole per kg or water where as osmolarity is meausres in osmole per litre of water
what is tonicity?
the effect a solution has on the volume of a cell
what is a solution called when there is no change in cell volume?
isotonic
what happens if a solution is hypotonic?
increase in cell volume
what happens if a solution is hypertonic ?
decrease in cell volume
what are the body fluid compartments ?
intracellular fluid - 67%
extracellular fluid -33%
what does the extracellular fluid contain?
plasma - ~20%
interstitial fluid - 80%
lymph and transcellular fluid (negligible)
what can be used to meausure volumes in the body fluid compartments?
tracers - specific chemicals which can be used to determinate the distribution volume
examples of tracers
TBW - 3H2O
ECF - inulin
Plasma - labelled albumin
what is the equation used to measure the volume of distribution?
Volume = Dose/ Sample Concentration
how is water balance controlled in our body?
homeostasis where water input = water output
what causes water imbalance?
changes in body fluid osmolarity
what are ways in which water is taken in ?
fluid intake
food intake
metabolism
what are ways in which water is outputted?
insensible loss - skin & lungs
sensible loss - sweat, faeces and urine
what are the general values of ionic composition of major fluid compartments?
more Na+ and Cl- outside the cell
more K+ inside
what is important about the osmolarity of the extra/intracellular fluids?
they are the same
what is fluid shift ?
movement of water between ICF and ECF in response to an osmotic gradient
what happens when he osmotic concentration o ECF increases?
- occurs when dehydrated
- took away water left the salt so ECF is hypertonic compared to the cell
- less water outside the cell so water will move from inside to outside so cell volume would decrease and the ECF would increase
what happens when the osmotic concentration of the ECF decreases?
- caused by over hydration
- more water in ECF than ICF so water move into cell resulting in increase cell volume and decreases ICF
what happens i there is a gain or loss of water?
change in fluid osmolarity so similar changes in ICF and ECF
what happens when there is a gain or loss of NaCl ?
change in fluid osmolarity resulting in Na+ excluded from ICF and osmotic water movements
how does ICF and ECF volumes change with a loos or gain of NaCl?
gain - increase ECF decrease ICF
loss - decrease ECF and increase ICF
what happens if there is a gain or loss of isotonic fluid ?
no change in fluid osmolarity only change in ECF volume
when does electrolyte balance occur?
rate of gain = rate of loss
why is electrolyte balance important?
- total electrolyte concentration can directly affect water balance
- the concentrations of individual electrolytes can affect cell functions
why are K|+ and Na+ important in electrolyte balance?
- major contributors to the osmotic concentrations of EFC and ICF
- directly affect the function of all cells
