physiology Flashcards
what is osmolarity
the concentration of osmotically active particles present in a solution
unit of osmolarity used for body fluids
mosmol/l
how would you calculate the osmolarity of 150mM of NaCl
molar concentration of the solution x number of osmotically active particles present
2 x 150 = 300 mosmol/l
name the 3 main types of osmotically active particles
ions, small molecules and proteins
what is the difference between osmolarity and osmolality
osmolarity - number of osmoles per litre of solution
osmolality - number of osmoles per kilogram of solvent
what is tonicity
the effect a solution has on the cell volume
isotonic solution
causes no change in cell volume
hypotonic solution
causes an increase in cell volume as water enters the cell
consequence of a hypotonic solution
cell lysis
hypertonic solution
causes a decrease in cell volume as water leaves the cell
consequence of hypertonic solution
cell shrinkage
what are the 2 major compartments of total body water
intracellular fluid - fluid inside the cells
extracellular fluid - plasma, interstitial fluid + lymph, CSF
what can be useful when determining the volume of body fluid compartments
tracers
what is the volume of distribution
determines how a drug distributes itself within the body
what does it mean if a drug has a low Vd
mainly stays in the plasma
what does it mean if a drug has a moderate Vd
distributes into extracellular fluid
what does it mean if a drug has a high Vd
drug extensively enters tissues
what can be used as a tracer in extracellular fluid
inulin
what can be used as a tracer in plasma
labelled albumin
what are the 3 main ions found in extracellular fluid
Na+, Cl- and HCO3-
what is interstitial fluid
the fluid surrounding the cells in tissues
describe the relationship between ICF, interstitial fluid and blood plasma
ICF | (plasma membrane) | interstital fluid
interstital fluid | (capillary wall) | plasma
what is fluid shift in the body
movement of water between the ICF and the ECF in response to an osmotic gradient
what happens to the ECF in a patient who is dehydrated and what is the consequence of this
becomes hypertonic
water moves out of cells into ECF so cells shrink