Control composition and Volume of ECF Flashcards
What determines the osmotic pressure generated by a solution
Molar conc of the solution - osmotic pressure is determined by number of active particles per unit volume not their size
what things are high in intracellular fluids
potassium , proteins and HPo4 and magnesium
more protein higher oncotic pressure - material end BP higher than osmotic pressure net pressure out and venous end osmotic pressure higher than blood pressure so net in
what is tonicity
Tonicity is the final osmotic pressure after any solute removal
Where is the bodys fluid distributed
Compartments divide ⅓ , ⅔
Whole body is 70kg - 70L
Solid is ⅓ and fluid is ⅔ - 45L
Fluid divided into intracelualr ⅔ - 30L and extracellular is 15L
Extracellular fluid can be divided into intravascular(5L) and interstitial space(10L)
Intravascular divides into plasma 3L and RBC so 2L
water moves between all somsosi maybe enhance by AQU - glucose though endoltheiul and readyily in most cells - plasma into interstitial or intracellular
what is pinocytosis
Pinocytosis - clathrin coated pits - proteins bind to receptor - invagination generated by actin and myosin activating so vesicle and delivered to cell for needed so could be neurotransmitter
release by ADH is controlled by
hypothalamic osmoreceptors - anti-diuretic
when plasma osmolarity rises, water leaves what cells causing shrinkage, tiegsgerign mechanically regulated ion channels causing an AP generation and stimulating ADH release from posterior pituitary
osmoreceptors in VOLT ( vascular organ of lamina terminals) outside BBB
Water goes out shrinking cell when plasma osmolarity risesSympatheic NS and angiotensin II also stimulate hypothalamus
if normal osmolarity increases by diarrhoea for example so increased ECF osmolarity - stimulates HYPOthalamic osmorecpors so paraventricular and supra-optic nuclei cause ADH release so CD permeable and more water retention by kidney
also stimulates lateral prep-tic area increasing thirst so dris water therefore returning osmolarity to normal
what happens when normal osmolarity decreases
normally by excessive fluid digestion so hypothalamic orsmorecptors ar inhibited so thirst is spurred by lateral prep-tic area and paravenricular and supra-optic nuclie suppress ADH release and CD made impermeable so increased water excretion
nicotine increase ADH secretion whereas alcohol decrease it
what aldosterone stimulate via gene expression
ENaC synthesis - increase sodium reabsorption and potassium excretion
ATPase pump to keep intracellular sodium down
what inhibits aldosterone release
ANP
Released by low pressure atrial stretch ( expanded blood volume ) to cause
Increase GFR
Aldosterone secretion reduced
Renin released reduced
Adh releases reduced
therefore increasing amount of sodium excretion
blood fluid disturbances are controlled by what
osmolarity ( if high ADH increased and retain water VV)
volume ( high aldosterone decreased but ANP increase so sodium is excreted more , vv)
what drugs retain sodium
fludrocortisone - agonist
antagonist is spironolactone
ADH - terlipressin - water
normal 0.9% saline contains what
154 sodium and chloride
hartmanns solution contains
131 sodium , 111 chloride and potassium 5
5% dextrose contains
278 glucose
in hyponatremia what IV should use use
dextrose- saline 0.18% - low sodium so cannot have tjhat as sodium is already below 120mmol/L - water retention leads to dilution causing HF , inappropriate ADH secretion ( SIADH) intake excess oil or IV
Hyponatremia sodium is below 120mmol/L in the serum - water retention leads to dilution - causes - heart failure , inappropriate ADH secretion (SIADH) - intake excess oral or IV
If it’s not fluid retention that has caused hyponatremia it may be due to sodium loss
Causes of this are diuretics, vomiting and diarrhoea or adrenal failure like in addison’s disease
