Acid Base Regulation - Columbo Flashcards
Arrhenius definition of acids/bases
Acids increase H+ ion concentration in aqueous solutions, bases increase OH- in aqueous solutions
Bronsted-Lowry definition of acids/bases
Acids donate protons, while bases accept protons (but do not necessarily increase OH- concentration_
Lewis definition of acids/bases
Acids accept electron pairs, bases donate electron pairs
Most acids/bases we consider in a physiological context are weak as opposed to strong. Why is this important?
Our ability to keep our pH regulated is due to the buffering capacity of our body fluids; strong acids/bases would make it much more difficult to buffer because they completely disassociate in solution
Biological processes that can be affected by changes in pH
- protein folding and conformation
- ion currents
- ligand-receptor interactions
- muscle contraction
- cell proliferation
What is the condition that results from an overabundance of H+ ions in the blood?
acidemia
What is the condition that results from a lowered H+ concentration in the blood?
alkalemia
what does pH describe about the relationship of conjugate base/acid in the blood?
the ratio between them, as opposed to the amount of each
3 ways H+ concentration in the blood serum is controlled
1) lungs can remove CO2
2) kidneys can remove H+, retain HCO3-
3) buffering resists pH change
* these are reversible in cases of alkalosis
What is a respiratory reaction of increased H+ ions (decrease in pH)?
-increase in alveolar ventilation
What is a respiratory reaction of decreased H+ ions (increase in pH)?
- respiratory depression and retention of CO2
- lowered O2 levels can stimulate respiration, so it has less of an impact
In terms of renal control of pH, is the retention of HCO3- or the excretion of H+ more important?
- retention of HCO3-
- the excretion of 1 HCO3- is the same as adding 1 H+
- HCO3- can bind a free H+ (acts as buffer), so retaining it will lower free H+
3 key buffer systems
1) bicarbonate - buffers extracellular fluid
2) phosphate - buffers intracellular fluid and kidney tubules
3) proteins - absorb free H+ ions in intracellular and extracellular environments (example is deoxy-hemoglobin in RBCs)
What is a buffer?
- a substance that is capable of absorbing or releasing H+ ions, helping solution resist pH change
- example: carbonic acid can disassociate to form 1 free H+ ion and bicarbonate, or the reverse can occur (we are either adding an H+ to lower pH, or absorbing an H+ to increase pH)
What is the Henderson-Hasselbalch equation?
pH = pKa + log [A-]/[HA]
- remember that the acid has more Hs
- if the ratio of [A-] to [HA] is equal, then pH = pKa
relative to the Henderson-Hasselbalch equation, when are buffers most effective?
pH = pKa + log [A-]/[HA]
- when pH = pKa
- aka when the ratio of [A-] to [HA] is equal
3 important regulators of intracellular pH
1) ion transporters
2) protein buffer system
3) phosphate buffer system
What can cause hypoventilation-induced acidosis?
- related to blood CO2 levels*
- obstructive lung diseases
- CNS trauma
- Narcotics
- insufficient ventilation
- polio
What can cause hyperventilation-induced alkalosis?
- related to blood CO2 levels*
- anxiety
- stroke
- pain
- over-ventilation
- hypoxemia
What can cause metabolic acidosis?
- related to blood HCO3- levels*
- diarrhea
- renal insufficiency
- excessive lactic acid
What can cause metabolic alkalosis?
- related to blood HCO3- levels*
- excessive vomiting
- hypokalemia
- mineralocorticoids
What is a mixed acid-base disorder?
- when more than one simple disturbance in acid-base exists
- example: one disturbance can cause both acidosis (respiratory or metabolic) and alkalosis (respiratory or metabolic)
