The Respiratory System Ventilation moving air into and out of lungs Gas exchange

1. The Respiratory System Ventilation moving air into and out of lungs Gas exchange diffusion through lung tissue Oxygen utilization in cell respiration

2. The conducting and respiratory zones

3. Properties of lungs Compliance- ability to expand when stretched Elasticity- ability to return to original size Surface tension exerted by fluid in alveoli Surfactant helps prevent alveoli from collapsing RDS-surfactant lacking in the lungs of premature babies ARDS- alveolar permeability and reduced surfactant

4. Ventilation is a mechanical process

6. Restrictive disorders- vital capacity is reduced; FEV is normal Obstructive disorders- FEV is reduced, vital capacity is normal, e.g., asthma Bronchoconstriction- resistance to air flow Inflammation- clogs air passages Emphysema- destruction of alveoli COPD- obstructive and restrictive; chronic bronchitis and emphysema

7. Partial pressures of oxygen and carbon dioxide Most O2 in blood is bound to RBCs (0.3ml out of 20 ml/100 ml blood is dissolved in plasma) Increasing PO2 in blood increases rate of diffusion to tissues Arterial levels are significant because they reflect lung function

9. Regulation of breathing • Voluntary • Somatic motor neurons controlled by centers in medulla oblongata and pons • Involuntary • Feedback from receptors that detect changes in blood chemistry

12. Chemoreceptor control of breathing • Mostly controlled by chemoreceptors in medulla • CO2 can cross blood-brain barrier • Increased CO2 lowers blood pH • Peripheral receptors are affected by H+ concentration • Oxygen levels do not change as fast

13. Blood CO2 levels are most immediately affected by changes in breathing (affects blood pH) Carotid and aortic bodies respond to changes in pH Oxygen levels do not change as fast Sensitivity to oxygen augments sensitivity to carbon dioxide (ventilation rate increases at high altitude)

14. Hemoglobin and oxygen transport Loading (in lungs) deoxyhemoglobin becomes oxyhemoglobin; reversed in tissues Affinity for oxygen decreases in lower pH and higher temperature 2,3-DPG (unique to RBCs) also reduces affinity of oxyhemoglobin for oxygen (this works if oxygen levels are low or in anemia) Net effect: favors unloading of oxygen into tissues

15. Carbon dioxide transport and acid-base balance Carbon dioxide is converted to carbonic acid by carbonic anhydrase in red blood cells Hydrogen ions are produced; these combine with hemoglobin This promotes unloading of oxygen from hemoglobin

18. pH balance Hypoventilation- acidosis Hyperventilation- alkalosis Normal blood pH is 7.35-7.45

19. Compensations for exercise and high altitude Exercise ventilation increased oxygen delivery to tissues increased by vasodilation increased temperature lowers affinity for oxygen so is released to tissues lactate threshold- higher in physically fit people (they have higher maximal oxygen uptake)

20. Adaptations to high altitude Polycythemia can be dangerous

21. Summary • Designed for ventilation, gas exchange, and transport of gases through blood • Muscles of respiration are controlled autonomically through medulla oblongata and pons • Chemoreceptors detect changes in carbon dioxide, hydrogen, and oxygen levels in the blood • Environmental factors affect affinity of hemoglobin for oxygen • Ventilation helps regulate acid-base balance in blood • Respiratory system adapts to “extremes” of exercise and high altitude