acid base balance Flashcards
what are the 3 major blood buffering systems ?
what is pk ?
equilibrium constant for a buffer system, where the concentration of acid = base.
The effective buffering range is ±1 pH unit around the pK value (linear portion of titration curve).
For bicarbonate: pK = 6.1 (range: 5.1–7.1).
For phosphate: pK = 7.2 (range: 5.8–7.8).
what are the advantages and disadvantages of a bicarbonate buffer ?
Advantages of the Bicarbonate Buffer System:
* The acid (CO₂) and salt (HCO₃⁻) forms of the buffer can be regulated independently:
* CO₂ excretion or retention is controlled by the lungs.
* HCO₃⁻ reabsorption and regeneration are controlled by the kidneys.
* A readily available supply of CO₂ from cellular metabolism.
Limitations of Buffers:
* Buffers are limited in capacity.
* As buffer capacity is used, less is available to control pH.
* The renal and respiratory systems are needed to eliminate excess H⁺ or base and restore normal buffer capacity.
how do the kidneys regulate acid base levels ?
✅ Filtration of HCO₃⁻ → Prevents bicarbonate loss.
✅ HCO₃⁻ Reabsorption (Proximal & Distal Tubule) → Conserves buffer.
✅ H⁺ Secretion (Collecting Duct & Tubules) → Removes excess acid.
✅ Bicarbonate Generation → Produces new HCO₃⁻ to maintain balance.
✅ Acid Excretion (H⁺ Buffers) → Uses phosphate & ammonium buffers.
Response to Imbalances:
✅ Acidosis (↓ pH): ⬆ H⁺ secretion, ⬆ HCO₃⁻ reabsorption.
Alkalosis (↑ pH): ⬇ H⁺ secretion, ⬆ HCO₃⁻ excretion.
✅ Goal: Maintain pH 7.35 - 7.45.
how do the kidneys regulate [H⁺] & [HCO₃⁻] ?
✅ Filtration of HCO₃⁻ at the glomerulus.
✅ Reabsorption of HCO₃⁻ (Proximal tubule & Distal tubule).
✅ Secretion of H⁺ (Collecting duct).
✅ Buffering of H⁺ (Phosphate & Ammonium systems).
✅ Response to pH changes (Acidosis: ⬆ H⁺ secretion, Alkalosis: ⬇ H⁺ secretion).
✅ Maintains blood pH (7.35 - 7.45).
Where is most bicarbonate (HCO₃⁻) reabsorbed in the kidney?
✅ Proximal tubule (~80-90%) – Main site of HCO₃⁻ reabsorption.
✅ Distal tubule & Collecting duct (~10%) – Fine-tunes balance.
✅ Prevents loss of bicarbonate, a key buffer.
How do the kidneys secrete H⁺ into urine?
✅ Collecting duct (Intercalated cells): Actively secretes H⁺.
✅ H⁺ secretion allows new HCO₃⁻ generation.
✅ Prevents blood from becoming too acidic.
How is H⁺ buffered in the urine?
✅ Phosphate Buffer: H₂PO₄⁻ → HPO₄²⁻ + H⁺ (Excretes H⁺ safely).
✅ Ammonium Buffer: NH₃ + H⁺ → NH₄⁺ (Ammonium excretion).
How do the kidneys respond to acidosis? (Low pH) ?
✅ ⬆ H⁺ secretion.
✅ ⬆ HCO₃⁻ reabsorption.
✅ Generates new HCO₃⁻ to neutralize excess acid.
✅ Uses phosphate & ammonium buffers to excrete H⁺.
How do the kidneys respond to alkalosis? (High pH) ?
✅ ⬇ H⁺ secretion.
✅ ⬇ HCO₃⁻ reabsorption.
✅ More HCO₃⁻ is excreted to lower pH.
how do the lungs and kidney compensate for acidosis ?
how do the lungs and kidney compensate for alkalosis ?
give a summary of metabolic and respiratory acidosis and alkalosis
