Flashcards in Acid Base regulation Deck (57):
Where does most of the acid come from within the body? What are the lesser sources?
Breakdown of metabolic products, producing CO2
Lesser = breakdown of proteins produces sulfuric/phosphoric acid
What are the three acids that are only secreted through the kidneys?
1. Phosphoric acid
2. Sulfuric acid
3. Lactic acid
What is the normal pH of the blood?
What are the two major organs responsible for regulating blood pH? How long does each take to change the acidity of the blood?
Lungs- fast acting
Kidneys - slow acting
What is the range of pH of urine? What does this depend on?
4.5- 8, depending on whether the kidney needs to excrete more acid or more base
What is acidemia?
Blood pH <7.35
What is acidosis?
Disease process or condition that acts to lower pH
What is alkalemia?
Blood pH >7.45
What is alkalosis?
Any disease process that raises pH
What is severe acidosis?
Blood pH <7
What is the highest pH that the body can tolerate?
What part of the diet can contribute to alkalosis? How?
Fruits, since they contain the salts of weak organic acids (Na, and K)
What is the immediate source of buffering changes in blood pH?
Body proteins (Hb)
If the pH decreases, what is the response by the respiratory system?
Respiratory center of the brain will increase ventilation to blow off CO2, to decrease carbonic acid
Respiratory acidosis is caused by what? (Hypoventilation or Hyperventilation?)
Respiratory alkalosis is caused by what? (Hypoventilation or Hyperventilation?)
Can metabolic acidosis/alkalosis be eliminated by respiratory compensation?
No, but can adjust
If acidosis/alkalosis is nonrespiratory it is called what?
How does the kidney compensate for metabolic alkalosis?
Excrete alkaline urine (HCO3)
How does the kidney compensate for metabolic acidosis?
Excreting acidic urine, and reabsorb all of the bicarbonate in the filtrate
What is a buffer?
A weak acid/base and its conjugate
What is the Henderson-Hasselbalch equation?
pH = pka+log(base/acid)
What is the equation for the bicarbonate buffer system? Walk through what would happen if [H] were to increase/decreases.
H2CO3 -> H +HCO3
If H increases, rxn shifts left
If H decreases, rxn shifts right
A buffer system acts best around what pH?
where pH = pKa
What is the buffer system used by the kidneys and intracellular fluid? What is its pKa?
Phosphate buffer system
pKa = 6.8
Why are proteins not part of the normal compensatory response to acid-base changes?
The amount of protein does not change in response to changes in the acid/base status of the body
Why is Q the main AA involved in the ammonium buffer system?
can be broken down to HCO3 to go the the blood, and NH4 to the tubular lumen
Where in the nephron is H+ secreted? (3) What is the mechanism behind this?
Proximal tubule, thick ascending tubule, and early distal tubule
What happens to the H+ secreted into the tubular lumen?
Reacts with HCO3 to produce bicarb.
Bicarb then converts to CO2 and H2O, and CO2 is picked up by the blood or converted to bicarb
How do we "reabsorb" bicarb from the nephron?
Pump out H, take in H2O that that makes, and react it with water to produce bicarb
For every H+ secreted into the tubular lumen, what happens?
a bicarbonate ion enters the blood
How do we increase bicarb [c] if there is no more bicarb left in the tubular lumen?
Use carbonic anhydrase to convert CO2 in the blood to bicarb, and pump out H ion into the tubular lumen. Cl is used to follow this.
What is the rxn that carbonic anhydrase catalyzes?
CO2 + H2O -> bicarb + H
How does the hydrogen phosphate system work in the tubular cells?
Same way as CO2 is excreted, but more inert compound produced (NaH2PO4)
What drives the dissociation of bicarb?
Drawing out H ions into the tubular lumen, which can be picked up by bicarb, phosphate, or excreted with Cl
What if we have reabsorbed all the bicarbonate and used up all the phosphate buffers that can be excreted but are still acidotic? What is the next system utilized?
The glutamine- NH4+ system can be used for compensating for extreme acidotic condition
What is the Q-NH4 system? Where does this take place in the nephron?
Q can be broken down into two bicarbs and two ammonium ions to be secreted into the urine
This is found in the proximal tubule
What is the process utilized later in the nephron to have the same effect as the Q-NH4 system?
ammonia is excreted to ensure urine is not too acidic
What is secreted in the urine if the body needs to get rid of acid?
H+ and NH4
What is secreted in the urine if the body needs to get rid of base?
How do the kidneys compensate for respiratory alkalosis? (hint, there is less CO2)
Reabsorb less bicarb; increase bicarb excretion
What are the axes of the Davenport diagram?
What happens to the davenport curve if you have an increase in baseline pCO2 (e.g. in COPD)
What happens to the davenport curve if you have an decrease in baseline pCO2?
Short term changes are reflected how on the Davenport diagram?
Shifts **along** the respiratory curve
Long term changes are reflected how on the Davenport diagram?
Shift of the metabolic curve
Review that graph and situations!
Review that graph and situations!
How do you differentiate between respiratory and metabolic acidosis in the clinic?
If change is due to pCO2, respiratory
If change is due to HCO change, then it is metabolic
What is the process of acid/base secretion used by the proximal tubules?
What is the process of acid/base secretion used by the collecting ducts?
What are the two buffers in the urine that can absorb excess H+ from the blood?
Phosphate and ammonium buffers
Where does the NH4 buffer come into play (proximal tubule or collecting duct)?
proximal tubule and thick limb
What AA is used to generate 2 NH4 and 2 HCO3 for the ammonium buffer system?
Is NH3 permeable to the cell membrane in the nephron? Is NH4?
NH3 is, but NH4 is not. Thus is hold H+ ions in the urine
When is the glutamine budder utilized?
Under extreme acidemia
What can hydrogen ions combine with (what are the buffers utilized)?
NH4 (from Q)