Acid Base Balance Flashcards
what is the average pH of blood?
7.4
what is the pH of ECF?
7.4
what effect can acidosis have on the CNS?
depression of the CNS
what effect can alkalosis have on the nervous system?
over excitability
how can the kidneys control plasma bicarbonate concentration?
reabsorb HCO3
can add new HCO3 to the blood
what does kidney control of bicarbonate concentration depend on?
hydrogen secretion into the tubule
how much hydrogen is filtered into the tubular fluid at normal pH?
very few
there aren’t many in the plasma
what cells secrete hydrogen ions into the filtrate?
proximal tubule
distal tubule
collecting duct
how much bicarbonate is present in normal filtrate?
a lot - as they are freely filtered
how are bicarbonate ions taken up by tubular cells?
combine with hydrogen in the tubular fluid to form carbonic acid, dissociates into CO2 and H2O which enter the cell by diffusion
what transporter secretes hydrogen ions into the tubular fluid normally?
the sodium hydrogen anti-porter
how is bicarbonate moved out of the tubular cell into the interstitial fluid?
H2O + CO2 reform carbonic acid, dissociates into bicarbonate + H
leaves by the sodium bicarbonate co transporter
when bicarbonate in the tubular fluid is low due to buffering an acidosis, what is the next most plentiful buffer available?
phosphate
how does phosphate act as a buffer in the tubular fluid?
binds to hydrogen ions forming an acid phosphate which is excreted from the body in the urine
what acts as a buffer in acidosis when all bicarbonate and phosphate has been used up?
ammonia
how does ammonia act as a tubular buffer?
combines with hydrogen to form ammonium ions which are excreted in urine