Lecture 14 Outline (Ch. 49)

2. Lecture 14 Outline (Ch. 49) • I. Overview • Respiration in different organism • III. Methods – bulk flow vs. diffusion • Gas exchange and partial pressures • Inhalation/exhalation • Brain control • Respiratory problems

3. Thought Question: If you are an athlete who trains at high elevations, what happens if you compete at a lower elevation?

4. Living things process energy Overview They need oxygen for this - Why?

5. Cellular respiration uses O2 and produces CO2 Overview Cell C6H12O6 + O2 CO2 + H2O + ATP energy Breathing – respiration supports this process by exchanging gasses

6. Exchanging gasses Gas Exchange Systems • Moist surface • Gasses dissolve in water to move in/out of cells • Thin • Large surface area

7. Who needs a respiratory system? I don’t! I do! Gas Exchange Systems Moist environment Small (or thin) Low energy demand Dryer environment Large or thick-bodied High energy demand

8. Respiratory systems enable gas exchange Gas Exchange Systems • Bulk flow • Fluids move in bulk • Air/water move to respiratory surface • Blood moves through vessels • Diffusion • Individual molecules move down concentration gradients • Gas exchange across respiratory surface • Gas exchange in tissues

9. Gills Gas Exchange Systems • Elaborately folded ( surface area) • Contain capillary beds • Gill size inversely related to [O2] • Large gills = low [O2] Aquatic gas exchange

10. Fish Efficiency Gas Exchange Systems • Dissolved O2 is < 1% of water (21% of air) • Countercurrent exchange increases efficiency

11. Terrestrial respiration Gas Exchange Systems • Internal • Stay moist & supported • Insects have tracheae • Air enters/exits through spiracles • Branching channels (trachioles) allow gas exchange with cells

12. Vertebrate respiration Gas Exchange Systems • Terrestrial use of lungs • Evolved from accessory respiratory organs of freshwater fish • Amphibians are weird • Remain tied to water • Larval gills to adult lungs • Moist skin transfers gasses

13. Reptiles & Mammals use lungs exclusively Gas Exchange Systems • Lack permeable skin • Lungs are more efficient • Especially birds!

14. Human Respiration Mammals Air enters through nose and mouth to pharynx Travels through larynx (voice box) Epiglottis directs travel

15. On to the lungs Human Respiration Air is warmed & cleaned • Dust & bacteria trapped by mucus • Swept up and out by cilia • Microscopic chambers provide enormous surface area • Surfactant keeps surface moist • Association with capillaries • Diffusion of gasses Trachea  Bronchi  Bronchioles  Alveoli

16. Diffusion Lungs • Blood arrives from pulmonary artery • Low in O2 • Higher concentration in air diffuses into blood • High in CO2 • Higher concentration in blood diffuses into air

17. Human Respiration • Gas exchange is driven by differences in pressures • Blood from body with low O2, has a partial oxygen pressure (PO2) of ~40 mm Hg • By contrast, the PO2 in the alveoli is about 105 mm Hg • Blood leaving lungs, thus, normally contains a PO2 of ~100 mm

18. CO2 Transport Transport of gasses • The Bohr Effect: • Hemoglobin binds more tightly to O2 when pH is increased and loosely when pH is decreased • CO2 binds hemoglobin loosely • Dissolved in plasma • Combines with H20 to form bicarbonate (HCO3-) • More CO2 = lower pH

19. O2 Transport Transport of gasses • CO binds more tightly to hemoglobin than O2 • Prevents O2 transport • Binds to hemoglobin • Removes O2 from plasma solution • Increases concentration gradient; favors diffusion from air

20. Breathing Mechanisms • Outside lung covered by the visceral pleural membrane • Inner wall of thoracic cavity lined with parietal pleural membrane • Space between called the pleural cavity • Thin space w fluid • Causes 2 membranes to adhere • Lungs move with thoracic cavity

21. Breathing Mechanisms • Inhalation: • Contraction of intercostal muscles expands rib cage • Contraction of diaphragm expands the volume of thorax and lungs • Thoracic cavity expands, produces negative pressure which draws air into the lungs

22. Breathing is involuntary Breathing Mechanisms • Controlled by respiratory center of the brain • Adjusts breath rate & volume based on sensory input • Maintain a constant concentration of CO2

23. Asthma Respiratory Problems • Chronic obstructive pulmonary disease (COPD) • Refers to any disorder that obstructs airflow on a long-term basis Smooth muscle in bronchioles becomes irritated and constricts or spasms Increased mucus Can lead to collapse Linked to air quality and allergies

24. Emphysema Respiratory Problems • Alveoli rupture or become brittle creating larger but fewer alveoli Reduces surface area available for gas exchange Labored and difficult breathing 80-90% of deaths linked with smoking

25. Bronchitis & Pneumonia Respiratory Problems Jim Henson, creator of the Muppets, died at age 53 from pneumonia Inflammations of respiratory passages & lungs Increase in mucus production, decrease in cilia Reduces air flow to alveoli Causes include bacteria, viruses, fungi, & parasites

26. Tuberculosis Respiratory Problems Bacteria attack and cause lesions on lung tissue

27. Smoking Lung cancer accounts for more deaths than any other form of cancer Caused mainly by cigarette smoking Lung cancer metastasizes rapidly – usually cancer has spread to other tissues before detected Chance of recovery poor: only 3% of patients survive > 5 yrs 3 of the Marlboro men died from lung cancer 200 different toxins! • Includes tar, carbon monoxide, formaldehyde

28. Lecture 14 Summary • 1. Respiration Overview (Ch. 49) • Diffusion • Insects • Gills • Birds, reptiles, mammals • 2. Airway Route & gas exchange (Ch. 49) • Hemoglobin • Partial pressures • 3. Control (Ch. 49) • Inhalation/exhalation • Brain control • 4. Respiratory Problems (Ch. 49) • Asthma, emphysema, lung cancer, bronchitis, pneumonia, tuberculosis