chapter 26 Flashcards
(33 cards)
potassium secretion depends on
plasma concentration
aldosterone
plasma concentration
high K+ in ECF drives K+ into principal cells
increased secretion and excretion
low K+ in ECF drives reabsorption
Aldosterone
Stimulates K+ secretion
adrenal cortex secretes aldosterone when K+ high in ECF
optimal ph of arterial blood
7.4
7.45 or higher: alkalosis
7.35 or lower : physiological acidosis
sources of H+ in diet
- ingested food
- metabolic processes: lactic acid, loading of CO2, phosphoric acid
chemical buffer systems
one or more compounds that resist changes in pH when strong acids or bases are introduced
release H+ when pH rises
binds H+ when pH drops
three important buffer systems
bicarbonate buffer system
phosphate buffer system
protein buffer system
bicarbonate buffer system
-important for ECF
-mixture of carbonic acid (weak acid) and bicarbonate salt (weak base)
what does bicarbonate salt do in chemical buffer system
-bicarbonate salts ties H+ -from a strong acid:
-converted to carbonic acid
-conversion of strong acid to weak acid lowers pH only slightly
what does carbonic acid do in chemical buffer system
-carbonic acid ties up OH- from a strong base and also releases H+ in the process
-converted to bicarbonate salt
-conversion of a strong base to weak base raises pH slightly
phosphate buffer system
important for ICF and urine
similar to the bicarbonate buffer system but uses diff weak acids and bases
what acid and base is used in phosphate buffer system
dihydrogen phosphate (weak acid)
monohydrogen phosphate (weak base)
protein buffer system
important for ICF and blood plasma
carboxyl groups can release H+ when pH rises
NH2 can bind H+ when pH decreases
amphoteric molecule
a single protein can function as either an acid or base
depends on the pH of the environment
respiratory regulation of H+ rising PCO2
activates the respiratory centers
respiratory rate and depth increases
pH rises as more CO2 is blown off
respiratory regulation of H+ decreasing PCO2
depress respiratory centers
respiratory rate and depth decreases
pH decreases as CO2 accumulates
renal regulation
important for long term acid base balance
primary mechanism of acid base balance: adjusting amount of bicarbonate in blood
A.reabsorbing HCO3-
- kidney tubule cells cannot reabsorb bicarbonate directly from the filtrate
-H2CO3 in tubule cell broken down into H+ and HCO3-
what happens to H+ and HCO3-
H+ secreted into filtrate
HCO3- generated in tubule cell is pumped into peritubular capillary
B.generating new bicarbonate
PCT and type A intercalated cells of collecting ducts can generate new bicarbonate ions to be pumped into plasma
C. secretion of bicarbonate
-Type B intercalated cells in collecting ducts can secrete bicarbonate ions while reclaiming H+ from the filtrate
- secretion of bicarbonate is not efficient : even in alkalosis, more bicarbonate reabsorbed than secreted
respiratory acidosis
PCO2> 45 mm Hg
Respiration is shallow/slow (hypoventilation)
caused by: many respiratory diseases/conditions
respiratory alkalosis
PCO2< 35 mm Hg
respiration is deep and fast
causes: stress/anxiety, pain
metabolic acidosis and alkalosis
any acid base imbalance that doesnt involve CO2
bicarbonate ions especially
