body fluids Flashcards
define electrolyte
a substance that separates into cations and anions when dissolved in water to produce an electrically conduction solution
what are the fluid compartments in the body?
ICF
ECF - plasma and interstitial fluid
how much of the body is water?
60%
how much of the body weight is ECF?
20%
how much of the body weight is ICF?
40%
what electrolytes are high in the ECF?
Na+ and Cl-
what electrolytes are high in the ICF?
K+
what forces determine the movement of water between fluid compartments?
osmotic pressure
hydrostatic pressure
what is osmotic pressure?
the pressure that’s sufficient to prevent the uptake of water
related to the number of particles in the solution
what is osmolality?
a measure of the number of osmotically active particles in solution - how much solute is free in solution
what are the three main sources of osmolarity in the body?
charged macromolecules and their counter ions
smaller metabolites and their counterions
small inorganic ions
how do animal cells control their osmolarity?
actively pumping out inorganic ions so that their cytoplasm has a lower conc than the ECF
what toxins inhibit the Na+/K+ ATPase?
oubain
what is tonicity?
the ability of an extracellular fluid to make water move into or out of a cell
what determines tonicity?
the solutes that do not enter the cell bc only these can exert oncotic pressure
define colloid
a large molecular weight particle present in a solution
what percent of water taken in is from food and drink?
90%
what percent of water taken in is from metabolism?
10%
how can water be lost in the body?
sweat
respiration
faeces
urine
what does aldosterone do?
controls reabsorption of sodium in the dct
what does ADH/vasopressin control?
water reabsorption in the collecting duct
explain the mechanism to correct low blood volume
detection by JGA secretes renin triggers angiotensin II release contrists arterioles releases aldosterone increases Na+ and water reabsorption
what is hyponatremia?
decrease in plasma electrolytes
what causes hyponatremia?
congenitive heart failure or kidney failure
over hydration
what is hypernatremia?
increase in plasma electrolytes
caused by dehydration
explain ecstasy induced hyponatraemia
body retains water and secretes sodium
causes swelling of the brain (angiodema)
women more likely to be affected bc of oestrogen
