#8 Acid Base Balance Flashcards
The pH of the ECF is tightly controlled between what pH?
7.35-7.45
how much H+ does a person generate every day?
1meq/kg per day
T/F The concentration of H+ in the body fluids is low?
true, 40neq/L
what pH is compatible with life?
6.8-7.8 pH
what is the major buffer in the body?
HCO3-
what is the function of carbonic anhydrase?
converts co2 and H20 into H2CO3
what is the henderson hasselbalch equation?
acid base: pH=6.1 + log [HCO3-]/[.03CO2]
changes in the pH as a result of HCO3- are termed?
metabolic acid base disorders
changes in the pH as a result of CO2 are termed?
respiratory acid base disorders
what primarily regulates HCO3?
the kidneys
what primarily regulates the co2?
the lungs
carbohydrates and fats in the presence of insulin and O2 result in what?
CO2 and H2O
what does it mean to be a volatile acid?
an acid derived from hydration of CO2. (Gases)
sulfuric acid, hydrochloric acid are examples of what?
non volatile acids
what forms when you combine KCO3 with sulfuric acid?
you form a salt
why do you want to form sodium salts?
because in this form you can excrete them in the kidneys
The net of the diet results in volatile/non volatile acid production?
non volatile
about how much H+ do we excrete in our urine per day?
70mmol/day (40 from NH4+ and 30 from titratable acids)
How do you secrete acids?
majority is in the kidneys as a salt (titratable acids) and as ammonium
what is the net urinary excretion equation?
acid excretion = titratable acids (bound to H+) +(NH4+) - HCO3
how much HCO3 is reabsorbed per day?
4321 meq/day
where is most bicarb reabsorbed?
in the proximal tubule
How is bicarb reabsorbed in the proximal tubule?
1) HCO3 is converted to H2O and CO2 by CA#4
2) both diffuse through the cell membrane and reform using CA#2
3) HCO3 diffuses back into interstitial space
which cells in the kidney secrete bicarb? reabsorb it?
secreted by beta intercalated cells
reabsorbed by alpha intercalated cells
one HCO3 recovered from the urinary space means how much buffering capacity in the blood?
Its a one to one ratio.
state where the bicarb is reabsorbed in the kidney and how much?
proximal=80% TAL=10% distal convoluted= 6% collecting duct = 4% (only .36 moles/day is lost)
which type of intercalated cell in the kidney is Na+ independent?
alpha intercalated cells
what do beta intercalated cells do with the HCO3 that they have?
they put it into the lumen to be excreted in return for a Cl-
on which side of the alpha intercalated cell do you find the H+/K+ antiporter? what about the H+ ATPase?
both are on the apical membrane so that the H+ can be excreted.
what does parathyroid hormone do to the kidney?
it inhibits the Na+/H+ antiporter in the PCT
what does hypokalemia do the H+ movement?
hypokalemia stimulates H+ secretion. Hyperkalemia inhibits H+ secretion.
If you excrete 60 mmol of titratable acid in one day, what amount of free HCO3 is liberated?
60 mmol because it is one to one.
where do you generate most of you new Bicarb?
in the PCT
T/F when the body is acidic it creates bicarb and excretes acids with the same general pathway?
True. This happens because when you form HCO3 from H2O and CO2, you end up having an extra H+. This hydrogen is transported across the membrane into the lumen where binds to an acid such as HPO4 and makes it H2PO4 and this traps it if in the collecting duct.
How can you make ammonia and HCO3 together de novo?
break apart glutamine
How much HCO3 do you get when you break down glutamine?
2 molecules of HCO3
you also get 2 molecules of NH4+
what happens when you add a H+ to ammonia in the collecting duct?
you get NH4 that has to be secreted. Anywhere else it can diffuse through.
what will happen if NH4 is not secreted in the urine?
the blood will take it to the liver to make urea which is not very toxic like ammonium. This requires HCO3
what happens to glutamate metabolism during acidosis?
I dont know! But, GLUTAMINE degradation increases to make more bicarb.
what stimulates NH4 production?
acidosis
hypokalemia
what causes renal tubular acidosis?
defects in proximal and distal tubular H+ secretion
inadequate NH4 production
what is the first line of defense against acid/base imbalances?
extracellular and intracellular buffering
what is the primary extracellular buffer?
HCO3 50-70%
bone, phosphate, and proteins are also effective
what is the second line of defense to defend against large changes in pH?
Respiration to increase or decrease co2
what is the third line of defense to normalize pH?
Kidney.
How does the kidney regulate acid base problems?
formation/excretion of HCO3 and H+
requires several days
increased glutamine breakdown
If the HCO3 drops by 1 mEq, how much does pCO2 drop?
1.2 decrease = 1mEq decrease in HCO3
its a 1.2 to 1 ratio
if you have a 1 mEq increase in HCO3 how does this affect pCO2?
.7 increase=1mEq increase in HCO3
in acute respiratory acidosis, if you see a 1 mEq increase in plasma HCO3, this is due to how much of a rise in CO2?
10mmHg higher than normal (short term)
In chronic respiratory acidosis, if you see a rise in HCO3 by 3.5 mEq, how much change in CO2 caused this?
this means that CO2 has risen 10 mmHg above the normal
during acute respiratory alkalosis, if you see a decrease in HCO3 by 2 mEq, how much change in CO2 can this be attributed to? what about chronic respiratory alkalosis?
1) an acute decrease of 2mEq HCO3 is due to a fall of 10mmHg of CO2
2) a chronic decrease of 5mEq HCO3 is due to a fall of 10 mmHg of CO2.
What is the normal HCO3 level?
24mEq
what is the normal CO2 level?
40mmHg
