Acid Base Balance In Fishes

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  • 1. ACID-BASE BALANCE IN FISHES FEROSEKHAN S FISHERIES SCIENCE CIFE,MUMBAI
  • 2. Introduction
    • Acid –base balance involves the maintenance of internal pH.
    • Regulation of acid –base homeostasis is of critical importance to fishes.
    • In order to achieve homeostasis, there must be a balance between the intake or production of hydrogen ions and the net removal of hydrogen ions from the body.
  • 3. CONT….
    • A delicate balance of fluids, electrolytes, and acids and bases is required to maintain good health.
    • This balance is called Homeostasis
  • 4. pH Review
    • pH = - log [H + ]
    • H + is really a proton
    • Range is from 0 - 14
    • If [H + ] is high, the solution is acidic; pH < 7
    • If [H + ] is low, the solution is basic or alkaline ; pH > 7
  • 5.
    • Acids are H + donors.
    • Bases are H + acceptors, or give up OH - in solution.
    • Acids and bases can be:
      • Strong – dissociate completely in solution
        • HCl, NaOH
      • Weak – dissociate only partially in solution
        • Lactic acid, carbonic acid
  • 6. Body Fluids
    • Intracellular fluid (ICF)
      • found within the cells of the body
      • constitutes 2/3 of total body fluid
      • major cation is potassium
    • Extracellular fluid (ECF)
      • found outside the cells
      • accounts of 1/3 of total body fluid
      • major cation is sodium
  • 7. The Body and pH
    • Homeostasis of pH is tightly controlled
    • Intracellular fluid = 7.2 – 7.5
    • Blood pH = 7.7 – 8.0
    • < 7.0 or > 8.5 death occurs
    • Acidosis (acidemia) below 7.4
    • Alkalosis (alkalemia) above 8.3
  • 8. pH of Fish Blood 7.7 8.0 Normal blood pH Alkalosis Acidosis 8.2 8.4 7.4 7.2 7.0
  • 9. Small changes in pH can produce major disturbances
    • Most enzymes function only with narrow pH ranges
    • Acid-base balance can also affect electrolytes (Na + , K + , Cl - )
    • Can also affect hormones
  • 10. The body produces more acids than bases
    • Acids take in with foods
    • Acids produced by metabolism of lipids and proteins
    • Cellular metabolism produces CO 2 .
    • CO 2 + H 2 0 ↔ H 2 CO 3 ↔ H + + HCO 3 -
  • 11. How the Body defends against fluctuations in pH
    • Three Systems in the body:
    • 1.Buffers in the blood
    • 2.Respiration through the gills
    • 3.Excretion by the kidneys
  • 12. Buffers in the Blood
    • Buffers are substances that neutralize acids or bases
    • Bicarbonate which is a base and carbonic acid in the body fluids protect the body against changes in acidity
    • These buffer systems serve as a first line of defense against changes in the acid-base balance
  • 13. Respiration through the gills
    • Carbon Dioxide which is formed during cellular metabolism forms carbonic acid in the blood decreasing the pH
    • When the pH drops respiration rate increases this hyperventilation increases the amount of CO2 exhaled thereby lowering the carbonic acid concentration and restoring homeostasis
  • 14. Excretion by the Kidneys
    • The kidneys play the primary role in maintaining long term control of Acid-Base balance
    • The kidney does this by selecting which ions to retain and which to excrete
    • The kidneys adjust the body’s Acid-Base balance
  • 15. Control of Acids
    • Buffer systems:
      • Take up H+ or release H+ as conditions change
      • Buffer pairs – weak acid and a base
      • Results in a much smaller pH change
  • 16. Cont…
    • 1. Extracellular buffer
    • - Bicarbonate , Ammonia
    • 2.Intracellular buffer
    • - Protein, Phosphate
  • 17. Bicarbonate buffer
    • Sodium Bicarbonate (NaHCO 3 ) and carbonic acid (H 2 CO 3 )
    • Maintain a 20:1 ratio : HCO 3 - : H 2 CO 3
    • HCl + NaHCO 3 ↔ H 2 CO 3 + NaCl
    • NaOH + H 2 CO 3 ↔ NaHCO 3 + H 2 O
  • 18. Phosphate buffer
    • Major intracellular buffer
    • H + + HPO 4 2- ↔ H 2 PO4 -
    • OH - + H 2 PO 4 - ↔ H 2 O + H 2 PO 4 2-
  • 19. Protein Buffers
    • Non-bicarbonate buffers (Nbbs) – plasma proteins and hemoglobin.
    • Includes hemoglobin, work in blood
    • Carboxyl group gives up H +
    • Amino Group accepts H +
  • 20. 2. Respiratory mechanisms
    • Exhalation of carbon dioxide
    • CO 2 solubility in water is 25 times higher than that of oxygen ,so CO 2 is easily lost to the envt.
    • CO 2 + H 2 0 ↔ H 2 CO 3 ↔ H + + HCO 3 -
    • Body pH can be adjusted by changing rate and depth of breathing.
  • 21. 3. Kidney excretion
    • Can eliminate large amounts of acid
    • Can also excrete base
    • Can conserve and produce bicarb ions
    • Most effective regulator of pH
    • If kidneys fail, pH balance fails
  • 22. Rates of correction
    • Buffers function almost instantaneously
    • Respiratory mechanisms take several minutes to hours
    • Renal mechanisms may take several hours to days
  • 23.  
  • 24.  
  • 25. Acid-Base Imbalances
    • pH< 7.4acidosis
    • pH > 8.3 alkalosis
    • The body response to acid-base imbalance is called compensation
    • Partial compensation if range is still outside norms.
  • 26. Compensation
    • If underlying problem is metabolic, hyperventilation or hypoventilation can help : respiratory compensation .
    • If problem is respiratory, renal mechanisms can bring about metabolic compensation.
  • 27. 7–8.0
  • 28. There are 4 Types of Acid-base Imbalances
    • 1.Respiratory Alkalosis
    • 2.Respiratory Acidosis
    • 3.Metabolic Alkalosis
    • 4.Metabolic Acidosis
  • 29. Respiratory Alkalosis
    • Is a decrease in CO2, decrease in H+ (Hydrogen ions) and in increase in pH
    • This condition can be caused by continuous fish movement or anxiety reaction
    • The body compensates by the gills slowing the respiration rate and kidneys excreting more bicarbonate
  • 30. Respiratory Acidosis
    • Is an increase in CO2, an increase in H+ and a decrease in pH
    • This condition can be caused by , restrictive or obstructive gill diseases
    • The body compensates by the gills increasing respiration rate and the kidneys by conserving bicarbonate ions and increasing renal net acid excretions
  • 31. Metabolic Alkalosis
    • Is a decrease in CO2, a decrease in H+ and an increase in pH
    • This condition can be caused by , increased ingestion of alkali
    • The body compensates by the gills creating a slow respiration rate and the kidneys excreting more bicarbonate
  • 32. Metabolic Acidosis
    • Is an increase in CO2, and increase in H+ and a decrease in pH
    • This condition can be caused by alkaline loss, excess acid production or ingestion
    • The body compensates by the gills increasing respiration rate and the kidneys increasing renal net acid excretion
  • 33.  
  • 34. Conclusion
    • Fishes are capable of regulating their internal pH using both internal buffering and transepithelial exchanges across the gills.
    • Though their Pco 2 and HCO 3 - are well below those found in mammals, they can tolerate a variety of acid-base challenges.
  • 35.
    • QUERIES ?