1. Comparative Vertebrate Physiology
Respiration:
Gas exchange

2. Gas transfer systems Components: 1. Breathing 2. Respiratory diffusion
3. Bulk transport
4. Cellular diffusion

3. Dalton’s Law PT = P1 + P2 + P3 etc.
Therefore each gas has a partial pressure (Pgas)
Pgas = % of total mixture

4. Dalton’s Law
Atmospheric air

5. Henry’s Law
Gases dissolve into liquid in proportion to their partial pressure and their solubility
[G] = Pgas x Sgas
Equilibrium will be reached (e.g. gases in the lung)

6. Gas solubility Air: CO2 > O2(1/20th) > N2 (1/2)
What if air had more CO2 than O2?

7. Alveolar gases
Air in alveoli contains:
Less O2, more CO2 & H2O

8. Why is gas composition different?
O2 diffuses into blood, CO2 in opposite direction
Humid air in conductive pathway
Air in alveoli a mixture of air from more than one breath
How to alter gas composition?
Increase rate and depth of breathing

9. Pressure gradients

10. Pressure gradients Oxygen pO2 in deoxygenated blood is 40 mmHg
pO2 in alveoli is 104 mmHg

11. Pressure gradients Carbon dioxide pCO2 in alveoli is 40 mmHg
pCO2 in deoxygenated blood is 45 mmHg

12. Pressure gradients
Relatively the same amount of O2 and CO2 are exchanged. Why?
ANSWER: Solubility

13. Ventilation-perfusion coupling

14. Gas transport in blood Methods
Dissolved in plasma (3 ml per liter) Problem: C.O. would need to be 80 l/min
Bound to a respiratory pigment (Hb) (200 ml per liter)
Hb carries both O2 and CO2 simultaneously

15. Hemoglobin structure
Oxy vs. deoxyhemoglobin

16. Oxygen transport in blood
Percent saturation
Deoxyhemoglobin: Hb is 75% saturated

17. Oxygen transport in blood
Lampreys have modified Hb (1 heme)
Why the sigmoidal shape with Hb?

18. Hb-O2 affinity Decreasing affinity
Bohr Effect: Decrease in pH or increase in PCO2

19. Hb-O2 affinity Decreasing affinity Binding to 2,3 DPG
Elevated temperature

20. Carbon dioxide transport
Ways to transport
Dissolved in plasma (7 - 10%)
Bound to Hb ( %) *
Bicarbonate ion ( %) ** ** ** *