1. Chapter 42 Circulation and Gas Exchange

2. Material Exchange The exchange of materials from inside to outside is an important function for organisms. The exchange of materials from inside to outside is an important function for organisms. It’s easy for unicellular organisms. It’s easy for unicellular organisms. It becomes more difficult for multicellular organisms. It becomes more difficult for multicellular organisms. Complex organ systems have evolved to move materials throughout an organism. Complex organ systems have evolved to move materials throughout an organism.

3. GAS Exchange in Animals RESPIRATORY SYSTEM RESPIRATORY SYSTEM –OXYGEN IS NEEDED FOR AEROBIC RESPIRATION –GAS EXCHANGE: UPTAKE OF O2 & DISCHARGE OF CO2 –RESPIRATORY MEDIUM: SOURCE OF OXYGEN  AMOUNT OF DISSOLVED O2 IN WATER LESS THAN IN THE AIR

4. RESPIRATORY SURFACE PART OF ANIMAL WHERE GAS EXCHANGE OCCURS PART OF ANIMAL WHERE GAS EXCHANGE OCCURS DIFFUSION DIFFUSION THIN AND LARGE MAXIMIZE DIFFUSION THIN AND LARGE MAXIMIZE DIFFUSION CELLS MUST BE BATHED IN WATER TO MAINTAIN PLASMA MEMBRANE CELLS MUST BE BATHED IN WATER TO MAINTAIN PLASMA MEMBRANE –SURFACES THUS ARE MOIST –SIZE INFLUENCED BY SIZE OF ANIMAL –ENDOTHERM HAS LARGER R.S. THAN ECTOTHERM OF SAME SIZE

6. Respiratory System EXTENSIVE FOLDING OR BRANCHING EXTENSIVE FOLDING OR BRANCHING –ENLARGENS SURFACE AREA FOR GAS EXCHANGE In animals that don’t respire through their skin, there are three common respiratory surfaces: In animals that don’t respire through their skin, there are three common respiratory surfaces: 1. Gills 1. Gills 2. Trachea 2. Trachea 3. Lungs 3. Lungs

7. 1. Gills Are out-foldings of the body surface suspended in water. Are out-foldings of the body surface suspended in water. Creates a large surface area Creates a large surface area They are loaded with capillaries. They are loaded with capillaries. Animals with gills ventilate them which moves water with a high concentration of O 2 over them. Animals with gills ventilate them which moves water with a high concentration of O 2 over them. This ventilation consumes a lot of energy!! This ventilation consumes a lot of energy!!

9. 1. Countercurrent Exchange Gills Blood moves in an opposite direction to the movement of water past the gills. Blood moves in an opposite direction to the movement of water past the gills. The O 2 transfer is highly efficient. The O 2 transfer is highly efficient. This is called counter-current exchange, and loads the blood with O 2. This is called counter-current exchange, and loads the blood with O 2. It keeps a diffusion gradient over the entire length of the capillary. It keeps a diffusion gradient over the entire length of the capillary.

10. PROBLEMS ASSOCIATED WITH WATER AS A RESPIRATORY MEDIUM O2 CONCENTRATIONS ARE LOW O2 CONCENTRATIONS ARE LOW THE WARMER, THE LES DISSOLVED OXYGEN IT CAN HOLD THE WARMER, THE LES DISSOLVED OXYGEN IT CAN HOLD THE SALTIER, THE LES DISSOLVED OXYGEN IT CAN HOLD THE SALTIER, THE LES DISSOLVED OXYGEN IT CAN HOLD OVERCOME BY VENTILATION OVERCOME BY VENTILATION FISH OPENS WATER, WATER PASSES THROUGH PHARYNX & OVER GILLS FISH OPENS WATER, WATER PASSES THROUGH PHARYNX & OVER GILLS (FISH EXPEND A LOT OF ENERGY VENTILATING GILLS!!) (FISH EXPEND A LOT OF ENERGY VENTILATING GILLS!!)

11. Terrestrial breathing: Air has advantages over water as a respiratory medium Higher O2 conc Higher O2 conc Gas exchange faster through air Gas exchange faster through air Less ventilation of Resp. Surfaces required Less ventilation of Resp. Surfaces required AND DISADVANTAGES: AND DISADVANTAGES: Resp surfaces continuously desiccate ( dry out) Resp surfaces continuously desiccate ( dry out) Evolution overcomes this problem: surfaces within animal) Evolution overcomes this problem: surfaces within animal)

12. 2. Tracheal System Found in insects. Found in insects. Tubes that branch through the body Tubes that branch through the body Delivers air to all body cells Delivers air to all body cells Air enters tracheae through pores (spiracles) at the surface, passes through smaller tracheoles; end at cellular membranes. Air enters tracheae through pores (spiracles) at the surface, passes through smaller tracheoles; end at cellular membranes. Air sacks Air sacks

13. 3. Lungs Restricted to one location in body. Restricted to one location in body. Circulatory system connects respiratory surface with all body cells. Circulatory system connects respiratory surface with all body cells. They have a dense net of capillaries immediately below the epithelium on the respiratory surface. They have a dense net of capillaries immediately below the epithelium on the respiratory surface.

15. Air Pathway Nares, pharynx, larynx, trachea, bronchi, bronchioles, alveoli Nares, pharynx, larynx, trachea, bronchi, bronchioles, alveoli It is like a tree tipped upside down. It is like a tree tipped upside down. The epithelial lining of the three major branches of the respiratory system are covered by cilia and a thin film of mucus. The epithelial lining of the three major branches of the respiratory system are covered by cilia and a thin film of mucus.

16. Air Pathway The mucus traps particulate matter and the cilia sweeps it out. The mucus traps particulate matter and the cilia sweeps it out. O 2 dissolves in the moist film covering the epithelium and quickly diffuses into the web of capillaries surrounding the alveolus. O 2 dissolves in the moist film covering the epithelium and quickly diffuses into the web of capillaries surrounding the alveolus. CO 2 diffuses in the opposite direction. CO 2 diffuses in the opposite direction.

17. Alveoli Tips of smallest bronchioles Clusters of dead-ended air sacs Site of gas exchange Surrounded by web of capillaries Diffusion by differences in partial pressures (air is only part oxygen/CO2) Diffusion by differences in partial pressures (air is only part oxygen/CO2) High to low High to low

18. Oxygen Transport By respiratory pigments in the blood By respiratory pigments in the blood Hemoglobin –most vertebrates Hemoglobin –most vertebrates –Reversible binding –Iron Cooperative unloading Cooperative unloading –Unloading of O2 from one heme group stimulates unloading from the other three in a hemoglobin molecule Bohr shift is the lowering of hemoglobin’s affinity for oxygen upon a drop in pH. Bohr shift is the lowering of hemoglobin’s affinity for oxygen upon a drop in pH. –This occurs in active tissues due to the entrance of CO2 into the blood Heme group Iron atom O 2 loaded in lungs O 2 unloaded In tissues Polypeptide chain O2O2 O2O2

19. Oxygen Transport Cooperative unloading Cooperative unloading –Unloading of O2 from one heme group stimulates unloading from the other three in a hemoglobin molecule Bohr shift is the lowering of hemoglobin’s affinity for oxygen upon a drop in pH. Bohr shift is the lowering of hemoglobin’s affinity for oxygen upon a drop in pH. –This occurs in active tissues due to the entrance of CO2 into the blood Heme group Iron atom O 2 loaded in lungs O 2 unloaded In tissues Polypeptide chain O2O2 O2O2

20. Carbon Dioxide Transport Most transported in the plasma as bicarbonate ions: HCO3- Most transported in the plasma as bicarbonate ions: HCO3- CO2 enters RBC’s CO2 enters RBC’s In RBC’s, CO2 converted into bicarbonate. In RBC’s, CO2 converted into bicarbonate. Then diffuses out of RBC’s into the plasma Then diffuses out of RBC’s into the plasma

21. Figure 42.30 Tissue cell CO 2 Interstitial fluid CO 2 produced CO 2 transport from tissues CO 2 Blood plasma within capillary Capillary wall H2OH2O Red blood cell Hb Carbonic acid H 2 CO 3 HCO 3 – H+H+ + Bicarbonate HCO 3 – Hemoglobin picks up CO 2 and H + HCO 3 – H+H+ + H 2 CO 3 Hb Hemoglobin releases CO 2 and H + CO 2 transport to lungs H2OH2O CO 2 Alveolar space in lung 2 1 3 4 5 6 7 8 9 10 11 To lungs Carbon dioxide produced by body tissues diffuses into the interstitial fluid and the plasma. Over 90% of the CO 2 diffuses into red blood cells, leaving only 7% in the plasma as dissolved CO 2. Some CO 2 is picked up and transported by hemoglobin. However, most CO 2 reacts with water in red blood cells, forming carbonic acid (H 2 CO 3 ), a reaction catalyzed by carbonic anhydrase contained. Within red blood cells. Carbonic acid dissociates into a biocarbonate ion (HCO 3 – ) and a hydrogen ion (H + ). Hemoglobin binds most of the H + from H 2 CO 3 preventing the H + from acidifying the blood and thus preventing the Bohr shift. CO 2 diffuses into the alveolar space, from which it is expelled during exhalation. The reduction of CO 2 concentration in the plasma drives the breakdown of H 2 CO 3 Into CO 2 and water in the red blood cells (see step 9), a reversal of the reaction that occurs in the tissues (see step 4). Most of the HCO 3 – diffuse into the plasma where it is carried in the bloodstream to the lungs. In the HCO 3 – diffuse from the plasma red blood cells, combining with H + released from hemoglobin and forming H 2 CO 3. Carbonic acid is converted back into CO 2 and water. CO 2 formed from H 2 CO 3 is unloaded from hemoglobin and diffuses into the interstitial fluid. 1 2 3 4 5 6 7 8 9 10 11

22. Elite Animal Athletes Migratory and diving mammals Migratory and diving mammals –Have evolutionary adaptations that allow them to perform extraordinary feats

23. Diving Mammals-seals, dolphins, whales Google Google –Stockpile O 2  Higher myoglobin concentration in their muscles  Large spleen-store blood –and deplete it slowly  Blood diverted FROM muscles  Pulse slows upon diving

24. Diving Mammals-seals, dolphins, whalesGoogle Image Result for http- -bp3_blogger_com-_5v0u3ocGyrY- RyLZteHqzUI-AAAAAAAAAxM- gkbrVHneoMk-s400- Cachalot_jpg.mht Google Image Result for http- -bp3_blogger_com-_5v0u3ocGyrY- RyLZteHqzUI-AAAAAAAAAxM- gkbrVHneoMk-s400- Cachalot_jpg.mhtGoogle Image Result for http- -bp3_blogger_com-_5v0u3ocGyrY- RyLZteHqzUI-AAAAAAAAAxM- gkbrVHneoMk-s400- Cachalot_jpg.mht

25. Breathing The diffusion of a gas depends on partial pressures. The diffusion of a gas depends on partial pressures. When water is exposed to air, the amount of gas dissolved in the water is proportional to the partial pressure in the air, and its solubility in water. When water is exposed to air, the amount of gas dissolved in the water is proportional to the partial pressure in the air, and its solubility in water. Gases always diffuse from regions of high partial pressure to regions of low partial pressure. Gases always diffuse from regions of high partial pressure to regions of low partial pressure.

26. How an Amphibian Breathes An amphibian such as a frog An amphibian such as a frog –Ventilates its lungs by positive pressure breathing, which forces air down the trachea

27. How a Mammal Breathes Mammals ventilate their lungs Mammals ventilate their lungs –By negative pressure breathing, which pulls air into the lungs Air inhaledAir exhaled INHALATION Diaphragm contracts (moves down) EXHALATION Diaphragm relaxes (moves up) Diaphragm Lung Rib cage expands as rib muscles contract Rib cage gets smaller as rib muscles relax Figure 42.24

28. Lung volume increases Lung volume increases –As the rib muscles and diaphragm contract

29. Breathing & Amount of air inhaled Tidal volume is the volume of air inhaled & exhaled with each breath.(.5 l) Tidal volume is the volume of air inhaled & exhaled with each breath.(.5 l) –Vital capacity: The MAXIMUM -- during forced breathing is 3-4.8L Residual volume is the amount remaining in the lungs after a forced exhale. Residual volume is the amount remaining in the lungs after a forced exhale.

30. Breathing Human breathing is mostly under autonomic control. Human breathing is mostly under autonomic control. 2 regions of the brain control this: 2 regions of the brain control this: –The pons and the medulla. The pons controls the medulla which sets a basic breathing rhythm. The pons controls the medulla which sets a basic breathing rhythm.

31. Breathing Sensors in the aorta and carotid arteries exert secondary control over breathing. Sensors in the aorta and carotid arteries exert secondary control over breathing. These sensors monitor O 2, CO 2 and blood pH. These sensors monitor O 2, CO 2 and blood pH. The pH is largely controlled by CO 2 levels. The pH is largely controlled by CO 2 levels.

32. Breathing When CO 2 levels increase, carbonic acid levels increase lowering the blood pH. When CO 2 levels increase, carbonic acid levels increase lowering the blood pH. When pH drops, the depth and rate of breathing increases helping to remove excess CO 2. When pH drops, the depth and rate of breathing increases helping to remove excess CO 2. O 2 levels only have an effect on breathing rate at high altitudes. O 2 levels only have an effect on breathing rate at high altitudes.

33. Breathing In addition to transporting O 2, hemoglobin helps transport CO 2 and assists in buffering. In addition to transporting O 2, hemoglobin helps transport CO 2 and assists in buffering. Respiring cells produce CO 2. Carbonic anhydrase catalyzes the reaction of CO 2 with H 2 O to form H 2 CO 3. Respiring cells produce CO 2. Carbonic anhydrase catalyzes the reaction of CO 2 with H 2 O to form H 2 CO 3. H 2 CO 3 dissociates into H + + HCO 3 - H 2 CO 3 dissociates into H + + HCO 3 - Most of the H + attaches to hemoglobin and other proteins minimizing the change in blood pH. Most of the H + attaches to hemoglobin and other proteins minimizing the change in blood pH.

34. Breathing HCO 3 - diffuses into the plasma. HCO 3 - diffuses into the plasma. As blood flows through the lungs, the process is reversed. As blood flows through the lungs, the process is reversed. Diffusion of CO 2 out of the blood shifts the chemical equilibrium in favor of the conversion of HCO 3 - to CO 2. Diffusion of CO 2 out of the blood shifts the chemical equilibrium in favor of the conversion of HCO 3 - to CO 2.