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ACID-BASE BALANCE

ACID-BASE BALANCE. pH is a measure of H + pH = - log [H + ] Importance: Chemical reactions. Acid + Base = Salt Water (NEUTRALIZATION REACTION: HCl + NaOH  NaCl + H 2 O ). pH SCALE. Logarithmic 1.0 to 14.0 7.0 = neutral (chemical) 7.4 = normal (biological) <7.0 (7.4) = acidic

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ACID-BASE BALANCE

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  1. ACID-BASE BALANCE • pH is a measure of H + • pH = - log [H +] • Importance: • Chemical reactions

  2. Acid + Base = Salt Water(NEUTRALIZATION REACTION: HCl + NaOH  NaCl + H2O)

  3. pH SCALE • Logarithmic • 1.0 to 14.0 • 7.0 = neutral (chemical) • 7.4 = normal (biological) • <7.0 (7.4) = acidic • >7.0 (7.4) = alkaline (basic) • body pH range = 7.35 to 7.45

  4. ACIDS AND BASES • Acid = releases H+ = proton donor • Base = accepts H+ = proton acceptor • Strong acid vs. weak acid • Strong base vs. weak base

  5. SOURCES OF H+ • Metabolic reactions • Carbon dioxide • Exercise acids • Food

  6. pH MAINTENANCE • Buffer systems • Respiratory system • Urinary system

  7. BUFFER SYSTEMS • Buffer = substance preventing extreme fluctuations of pH • Strong acids/bases to weak ones • Work in buffer pairs; a base and an acid • Action: • BB + strong acid weak acid + salt • BA + strong base weak base + water • Systems: bicarbonate; phosphate; protein

  8. BICARBONATE BUFFERS • Important in blood • Buffer pair = NaHCO3/H2CO3 • HCl + NaHCO3 H2CO3 + NaCl • NaOH + H2CO3 NaHCO3 + H2O

  9. PHOSPHATE BUFFERS • Important in kidney • Buffer pair = Na2HPO4/NaH2PO4 • HCl + Na2HPO4 NaH2PO4 + NaCl • NaOH + NaH2PO4 Na2HPO4 + H2O

  10. PROTEIN BUFFERS • Important in cells • Amphoteric • Side groups: • COOH acts as acid – donates H+ • NH2 acts as base – accepts H + • Hb can act as a buffer

  11. Respiratory Control of pH • Review respiratory centers of brain • Review respiratory equation • Review chemoreceptors • It is fast acting when buffers need help • Control lasts relatively short time • NOT a long term solution • H+ = pH = resp. equation left = ventilation • Consider the opposite scenario

  12. Renal Control of pH • Kidney slow to respond to pH changes • Responds only after persistent changes • Compensates for a relatively long period • NOT a solution to chronic pH problems • Rids the body of H+ by tubular secretion • PCT, DCT, CD • Also: • Reabsorption of HCO3- • Regulation of PO4-3 • Production and elimination of NH3

  13. Summary of Kidney Action Blood Tubule Cells Filtrate CO2 CO2+ H2O H2CO3- HCO3- + H + H + + Na2HPO4 Na+ +NaH2PO4 HCO3- + Na+ Na+ NH3 NH3 + H+ (for excess H+) NH4+

  14. Coupling of H+ Secretion &Reabsorption of HCO3- p. 1007

  15. Buffers & New HCO3- p. 1008

  16. New HCO3- & Ammonia p. 1009

  17. Acidosis & Alkalosis • Look at the listed values in the above order

  18. Acidosis & Alkalosis

  19. Compensation • One system helping another to alleviate an acid/base problem: • An overload of the buffer system results in an increase in breathing rate; the respiratory system is compensating.

  20. Fluids & Electrolytes • Body water content • Fluid compartments: • Intracellular • Extracellular • Plasma • Interstitial fluid

  21. Fluid Compartments p. 1041

  22. Fluid Composition • Electrolytes • Nonelectrolytes • Comparison of intracellular & extracellular

  23. Fluid Composition • Note sodium and potassium • Note similarity of plasma & interstitial fluid except for protein p. 1043

  24. Fluid Movement • Water follows osmotic and hydrostatic pressure gradients

  25. Fluid & Solute Movement p. 1037

  26. Water Balance • Input must equal output p. 1037

  27. Regulation of Water Intake p. 1038

  28. Disorders of Water Balance • Dehydration • Water loss exceeds intake; When? • Diabetes • Decreased volume = hypovolemic shock • Water movement out of cells • Hypotonic hydration (Water intoxication) • Excess water • Diluted ECF • hyponatremia • Edema

  29. Disorders of Water Balance p. 1040

  30. Electrolyte Regulation - Sodium p. 1043

  31. ADH Action p. 1039

  32. Water: Pressure /Volume Relationships p. 1039

  33. Water: Pressure /Volume Relationships p. 1045

  34. Respiratory Centers • Medulla • Pons • Apneustic – works to smooth transition between inspiration and expiration • Pneumotaxic (pontine respiratory group) • Inhibits respiratory center • fine tunes rhythm • Prevents overinflation

  35. END

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