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Steps of Respiration

Steps of Respiration. Ventilation Gas Exchange Gas transport (circulatory system) Gas Exchange O 2 Utilization, CO 2 production (cellular respiration). 1. 2. 3. 4. 5. O 2. O 2. O 2. O 2. CO 2. CO 2. CO 2. CO 2. Diffusion of gases.

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Steps of Respiration

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  1. Steps of Respiration • Ventilation • Gas Exchange • Gas transport (circulatory system) • Gas Exchange • O2 Utilization, CO2 production (cellular respiration) 1 2 3 4 5

  2. O2 O2 O2 O2 CO2 CO2 CO2 CO2 Diffusion of gases • Concentration gradient & pressure drives movement of gases into & out of blood at both lungs & body tissue • Gases move from high partial pressure to low partial pressure capillaries in muscle capillaries in lungs blood lungs blood body

  3. Pgas = Patm x Fgas Partial Pressure • The total pressure of a mixture of gases (assuming constant temperature and volume) is dependent upon the number of moles of each gas in the mixture. • Partial Pressure • The contribution of each gas to the total pressure of a mixture of gases • Is dependent upon • Patm pressure exerted by the atmosphere(atmospheric pressure) • Fgas the fraction of gas (concentration of gas) in %

  4. Partial Pressure of Gases: Sea Level vs. Mount Everest Sea Level Mount Everest Patm = 250 mmHg Same gas concentrations (Fgas) Inhale PO2 = 250 mmHg x 0.2093 = 52 mmHg • Patm = 760 mmHg • Fgas 79.04% N2, 20.93% O2, 0.03% CO2 • Inhale • PN2 = 760 mmHg x 0.7904 = 600.70 mmHg • PO2 = 760 mmHg x 0.2093 = 159 mmHg • PCO2 = 760 mmHg x 0.0003 = 0.23 mmHg • Exhale • PN2 = 600.70 mmHg • PO2 = 130.95 mmHg • PCO2 = 28.12 mmHg Pgas = Patm x Fgas

  5. PO2<40 PCO2>45 Tissue Cells

  6. We Have a Problem… • 1L of arterial blood (at sea level) contains • 3 mL dissolved O2 • At rest the heart pumps • 5L of blood/min (cardiac output) • Therefore, a total of 15 mL of O2 is carried/dissolved in blood/min • At rest we need approx. 250 mL O2/min • NOT ENOUGH O2 DISSOLVED IN BLOOD!

  7. The Solution = Hemoglobin! • Hb acts as a “sink” to keep PO2 as low as possible • Maintains gradient for diffusion of O2 PO2 = PO2 PO2 > PO2 PO2 = PO2 B B A B A A Hb Hb

  8. Hemoglobin • Why use a carrier molecule? • O2 not soluble enough in H2O for animal needs • blood alone could not provide enough O2 to animal cells • maintain gradient for diffusion of O2 • hemocyanin in insects = copper (bluish/greenish) • hemoglobin in vertebrates = iron (reddish) • Reversibly binds O2 • loading O2 at lungs or gills & unloading at cells heme group deoxyHb oxyHb

  9. Cooperativity in Hemoglobin • Binding O2 • binding of O2 to 1st subunit causes shape change to other subunits • conformational change • increasing attraction to O2 • Releasing O2 • when 1st subunit releases O2, causes shape change to other subunits • conformational change • lowers attraction to O2

  10. What determines O2 Carrying Capacity of Blood? • PO2 in air/tissues/veins/arteries • High PO2 = high % Hb saturation • Low PO2 = low % Hb saturation • Amount of Hb in RBC PO2<40 PCO2>45 Tissue Cells

  11. 100 pH 7.60 90 pH 7.40 pH 7.20 80 70 60 More O2 delivered to tissues 50 % oxyhemoglobin saturation 40 30 20 10 0 0 20 40 60 80 100 120 140 PO2 (mm Hg) O2 dissociation curve for hemoglobin Effect of pH (CO2 concentration) Bohr Shift • drop in pHlowers affinity of Hb for O2 • active tissue (producing CO2) lowers blood pH • induces Hb to release more O2

  12. 100 20°C 90 37°C 43°C 80 70 More O2 delivered to tissues 60 50 % oxyhemoglobin saturation 40 30 20 10 0 0 20 40 60 80 100 120 140 PO2 (mm Hg) O2 dissociation curve for hemoglobin Effect of Temperature Bohr Shift • increase in temperaturelowers affinity of Hb for O2 • active muscle produces heat • Induces Hb to release more O2

  13. Consider the following… • Changes in PO2 at low levels of Hb saturation produce large changes in Hb saturation • Changes in PO2 at high levels of Hb saturation produce very small changes in Hb saturation At sea level: % Hb saturation~ 97-100% On Mt. Everest: % Hb saturation~ 10%

  14. Useless Useful

  15. Acclimation to Altitude • Immediately • Increased tidal volume, increased amount of air moved in and out of alveoli • Couple of Days • Decrease body H2O  increase % RBC  increase O2 carrying capacity • Within 7-10 days • Increased capillary density around cells • Increase mitochondrial concentration • Increased RBC synthesis due to kidney secreting EPO  increased Hb  increased O2 carrying capacity

  16. Tissue cells CO2 Carbonic anhydrase CO2 dissolves in plasma CO2 + H2O H2CO3 H2CO3 H+ + HCO3– CO2 combines with Hb Cl– HCO3– Plasma Transporting CO2 in blood • Dissolved in blood plasma as bicarbonate ion • High PCO2 in tissues carbonic acid CO2 + H2O  H2CO3 bicarbonate H2CO3  H+ + HCO3– carbonic anhydrase 60% 10% 30% HbCO2 (carbamino Hb) This equation is reversible!

  17. Lungs: Alveoli CO2 CO2 dissolved in plasma CO2 + H2O H2CO3 HCO3 – + H+ H2CO3 Hemoglobin + CO2 HCO3–Cl– Plasma Releasing CO2 from blood at lungs • Lower CO2 partial pressure at lungs allows CO2 to diffuse out of blood into lungs carbonic acid CO2 + H2O H2CO3 bicarbonate H2CO3 H+ + HCO3– carbonic anhydrase

  18. Adaptations for pregnancy • Mother & fetus exchange O2 & CO2 across placental tissue

  19. Fetal hemoglobin (HbF) • HbF has greater attraction to O2 than Hb • low % O2 by time blood reaches placenta • fetal Hb must be able to bind O2 with greater attraction than maternal Hb What is the adaptive advantage?

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