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Physiology Lecture 20

Physiology Lecture 20. Tanveer Raza MD MS razajju@yahoo.com. Oxygen-Hemoglobin Dissociation Curve. Oxygen-Hemoglobin Dissociation Curve. Oxygen-Hemoglobin Dissociation Curve. Arterial end of tissue capillaries (PO 2 = 95 mm Hg, 97% saturated Hb) 19.4 ml/ 100 ml blood

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Physiology Lecture 20

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  1. Physiology Lecture 20 Tanveer Raza MD MS razajju@yahoo.com

  2. Tanveer Raza MD MS MBBS razajju2@yahoo.com

  3. Oxygen-Hemoglobin Dissociation Curve Tanveer Raza MD MS MBBS razajju2@yahoo.com

  4. Oxygen-Hemoglobin Dissociation Curve Tanveer Raza MD MS MBBS razajju2@yahoo.com

  5. Oxygen-Hemoglobin Dissociation Curve Arterial end of tissue capillaries (PO2= 95 mm Hg, 97% saturated Hb) 19.4 ml/ 100 ml blood Venous end of tissue capillaires (PO2 =40 mm Hg, 75% saturated Hb) - 14.4 ml/ 100ml blood O2 released from Hb, under normal conditions = 5 ml/ 100 ml blood Tanveer Raza MD MS MBBS razajju2@yahoo.com

  6. Oxygen-Hemoglobin Dissociation Curve • During Strenuous Exercise, O2 released from Hb can be = 15 ml/ 100 ml blood (PO2 =15 mm Hg) Tanveer Raza MD MS MBBS razajju2@yahoo.com

  7. Utilization Coefficient • Percentage of blood that gives up O2 as it passes through the tissue capillaries is called the utilization coefficient • Normal value about 25% 5 ml/ 100 ml blood • During strenuous exercise 75 – 85% 15 ml/ 100 ml blood • In local tissue where • Extremely slow blood flow • Very high metabolic rate 100% Tanveer Raza MD MS MBBS razajju2@yahoo.com

  8. “Tissue oxygen buffer" system • Maintains Nearly Constant tissue PO2 • Atmospheric O2 Concentration Changes • Hb Buffer Effect maintains almost constant tissue PO2 • Tissue demand • Steep slope of the oxygen-hemoglobin dissociation curve • Increased tissue blood flow Tanveer Raza MD MS MBBS razajju2@yahoo.com

  9. “Tissue oxygen buffer" system • Maintains Nearly Constant tissue PO2: Atmospheric O2 Concentration Changes • In high altitude PO2 can fall half of normal. When alveolar PO2=60 mmHg, arterial Hb is still 89% saturated with O2. So, tissue PO2changes little Tanveer Raza MD MS MBBS razajju2@yahoo.com

  10. “Tissue oxygen buffer" system • Maintains Nearly Constant tissue PO2: Atmospheric O2 Concentration Changes • In deep sea (compressed air), PO2 may rise 10 times. When alveolar PO2=500 mmHg, O2 saturation of Hb can never rise above 100%, (only 3% above normal level of 97%). So, tissue PO2changes little Tanveer Raza MD MS MBBS razajju2@yahoo.com

  11. “Tissue oxygen buffer" system Tanveer Raza MD MS MBBS razajju2@yahoo.com

  12. Oxygen-Hemoglobin Dissociation Curve Shift of Oxygen-Hemoglobin dissociation curve to the right Tanveer Raza MD MS MBBS razajju2@yahoo.com

  13. Oxygen-Hemoglobin Dissociation Curve Shift of Oxygen-Hemoglobin dissociation curve to the right • Increase in H+ • Blood becomes acidic (decrease in pH) • Increased CO2 concentration • Increased blood temperature • Increased BPG Tanveer Raza MD MS MBBS razajju2@yahoo.com

  14. Oxygen-Hemoglobin Dissociation Curve Shift to the right • The Bohr EffectIncrease in H+ (decreased pH) and Increased CO2 concentration shifts the Curve to the right • Enhances 02 release from tissues Increased Delivery of O2to the Tissues by enhancing release of O2 from blood Tanveer Raza MD MS MBBS razajju2@yahoo.com

  15. Oxygen-Hemoglobin Dissociation Curve Shift to the right • The Bohr Effect • As the blood passes through tissues • Increased delivery of O2 to tissues • As the blood passes through lungs • Opposite effect: Increased transport of O2 by blood Tanveer Raza MD MS MBBS razajju2@yahoo.com

  16. Oxygen-Hemoglobin Dissociation Curve Shift to the right • The Bohr Effect • As the blood passes through tissues • Increased CO2in blood • CO2diffuses from tissue cells into blood • Increased H+ • CO2+H20=H2CO3=HCO3+H+ The curve shifts to the right causing decreased O2 combination with Hb and therefore delivering increased amounts of O2 to tissues • As the blood passes through lungs Tanveer Raza MD MS MBBS razajju2@yahoo.com

  17. Oxygen-Hemoglobin Dissociation Curve Shift to the right • The Bohr Effect • As the blood passes through tissues • As the blood passes through lungs • Decreased CO2in blood • CO2diffuses from blood into alveoli • Decreased H+ The curve shifts to the left causing increased O2 combination with Hb, thus greater transport of O2 Tanveer Raza MD MS MBBS razajju2@yahoo.com

  18. Oxygen-Hemoglobin Dissociation Curve Shift to the right • Increased BPG • BPG (2,3-biphosphoglycerate) • In hypoxia BPG in blood increases, thus shifting the curve to the right • More O2 released in hypoxic condition Tanveer Raza MD MS MBBS razajju2@yahoo.com

  19. Oxygen-Hemoglobin Dissociation Curve During Exercise the curve shifts to the RIGHT • The Bohr Effect • Increased H+ • Exercising muscles, release large quantities of CO2 and several other acids, increase H+ concentration in muscle capillary blood. • Increased temperature • Muscle temperature often rises 2-3°C • Increased BPG Tanveer Raza MD MS MBBS razajju2@yahoo.com

  20. Metabolic Use of Oxygen by the Cells • Metabolic use of O2 is controlled by • Rate at which ADP is formed • Diffusion distance from capillary to Cell • Usually pathological • Blood Flow Tanveer Raza MD MS MBBS razajju2@yahoo.com

  21. Transport of O2 in Dissolved State • 3% of total of O2 transported in dissolved state • During strenuous exercise, transport in dissolved state falls to as little as 1.5% • Oxygen poisoning • If person breathes O2 at very high PO2, amount transported in the dissolved state can become much greater, sometimes so serious causing brain convulsions and even death • Example: high-pressure breathing of oxygen among deep-sea divers Tanveer Raza MD MS MBBS razajju2@yahoo.com

  22. Carbon Monoxide poisoning • CO combines with Hb (HbCO) at the same point as O2 • Decreased O2 carrying capacity of blood • Displaces O2 from Hb • CO binds about 250 times more than O2 • Less O2 released from blood • Binding of CO at one of the 4 binding sites of Hb for O2 causes shift of dissociation curve to the left • Less oxygen released Tanveer Raza MD MS MBBS razajju2@yahoo.com

  23. CO2 transport

  24. CO2 transport • Transported in greater quantities than O2 • Amount in blood depends on acid-base balance of body fluids • In normal conditions amount transported from tissues to lungs is = 4ml/ 100ml of blood Tanveer Raza MD MS MBBS razajju2@yahoo.com

  25. CO2 transport Tanveer Raza MD MS MBBS razajju2@yahoo.com

  26. Forms in which CO2 is transported • In the form of HCO3- • About 70% • Dissolved state • About 7% • Combination with Hb and Plasma Proteins • About 20% Tanveer Raza MD MS MBBS razajju2@yahoo.com

  27. Forms in which CO2 is transported In the form of HCO3- • Dissolved CO2 reacts with H2O to form H2CO3 • Catalyzed by carbonic anhydrase inside RBC’s • H2CO3 dissociates into H+ and HCO3- • Most of the H+ combine with Hb (powerful acid-base buffer) Tanveer Raza MD MS MBBS razajju2@yahoo.com

  28. Forms in which CO2 is transported In the form of HCO3- • CHLORIDE SHIFT • Many HCO3- diffuse from RBC into plasma in exchange for Cl-, due to bicarbonate-chloride carrier protein in RBC membrane • Thus, Cl- content of Venous RBC’s > Arterial RBC Tanveer Raza MD MS MBBS razajju2@yahoo.com

  29. Forms in which CO2 is transported In Dissolved State • Quantity of CO2 normally transported in dissolved state is about = 7% of total = 0.3ml of CO2 /100ml blood Tanveer Raza MD MS MBBS razajju2@yahoo.com

  30. Forms in which CO2 is transported In Combination with Hb and Plasma Proteins-Carbaminohemoglobin 20% of total • CO2 + amine radicals of Hb = CO2 Hgb (carbaminohemoglobin) • Reversible reaction. CO2 is easily released into alveoli Tanveer Raza MD MS MBBS razajju2@yahoo.com

  31. THANK YOU Tanveer Raza MD MS MBBS razajju2@yahoo.com

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