measuring GFR and base balance Flashcards
what makes GFR equivalent to the clearance of a drug
known amount of plasma and
not metabolised
not absorbed or secreted
excreted unchanged in urine
how to assess GFR
look at concentration of nitrogenous waste products in the blood
what are 2 nitrogenous waste products
creatine and urea
characteristics of creatine
synthesised at a continual steady rate
production not influenced by many factors
freely filtered in glomerulus
no reabsorption
no secretion
what happens to creatine when GFR is reduced
less creatine excreted and will accumulate in plasma
characteristics of urea
main waste product of animals
water soluble
v small molecule
partially fat soluble
freely filtered through glomerulus
where is urea synthesised
liver
lipid solubility of urea
moderate lipid soluble
what is azotaemia
increased nitrogenous waste products in the blood
marker of decreased GFR
what type A intercalated cells are active on the apical membrane of the DCT
H+ ATPase
H+K+ ATPase
what are protons and bicarbonate formed from
dissociation of carbonic acid
what do protons that have been pumped into urine bind to
bicarbonate buffers
intercalated B cells on basolateral membrane
H+ ATPase
H+K+ ATPase
when do type A intercalated cells in the DCT work
increased H+ in interstitial space
=acidosis
when do type B intercalated cells in the DCT work
when H+ decreased in interstitial space
= alkalosis
what is pH
a measure of the concentration of protons
what does metabolism result in
production of protons
what is the single biggest input of protons under normal conditions
metabolic CO2
what do buffer systems do
act quickly to temporarily bind excess H+ or OH- hiding the highly reactive ions until they can be permanently secreted.
what does changing the rate and depth of breathing do
CO2 is exhaled or retained and blood pH is corrected
limits of respiratory system for correction of acid-base balances
only functions when respiratory system and control centres working normally
availability of bicarbonate ions
cannot protect ECF from pH changes due to increased or depressed CO2 levels (cannot buffer itself)
slowest mechanism
kidney excretion/reabsorption of acidic ions or basic ions
what is respiratory acidosis
when CO2 accumulates because of hypoventilation
what is metabolic acidosis
occurs whenever non-respiratory acids accumulate or the acid load normal but bicarbonate deficient.
