1. Respiration
Chapter 53
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2. Fick’s Law of Diffusion
Gas exchange is accomplished by diffusion
Rate of diffusion between two regions is governed by Fick’s Law.
R = D x A ( p/d)
R = Rate of diffusion
D = Diffusion Constant
A = Area over which diffusion takes place.
p = Differences in concentrations
d = Distance across which diffusion takes place.
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3. How Animals Maximize the Rate of Diffusion
Beating cilia producing water current.
Respiratory organs that increase surface area available for diffusion.
Bring external environment close to internal fluid.
Atmospheric Pressure and Partial Pressures
One atmosphere is 760 mm Hg.
Partial Pressure is fraction contributed by a gas.
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4. The Gill as a Respiratory Structure
External gills provide a greatly increased surface area for gas exchange.
Disadvantages are that they must be moved constantly and are easily damaged.
Gills of Bony Fish
Located between buccal cavity and opercular cavity.
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5. The Gill as a Respiratory Structure
Buccal cavity can be opened and closed by opening and closing the mouth.
Opercular cavity can be opened and closed by movements of the operculum.
Ram ventilation
Blood flows in an opposite direction to the flow of water, thus maximizing oxygenation of blood.
Countercurrent Flow.
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6. Respiration in Air-Breathing Animals
Gills replaced in terrestrial animals because:
Air is less buoyant than water.
Water vapor diffuses into the air through evaporation.
Two Main terrestrial respiratory organs:
Tracheae
Lung
Lungs use a uniform pool of air in constant contact with gas exchange surface.
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7. Respiration in Amphibians and Reptiles
Lungs of amphibians are formed as saclike outpouching of the gut.
Amphibians force air into their lungs creating positive pressure.
Fill buccal cavity with air, and then close mouth and nostrils and elevate floor of oral cavity.
Reptiles expand their rib cages by muscular contraction and take air into lungs via negative pressure breathing.
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8. Respiration in Mammals
Lungs of mammals packed with Alveoli.
Air brought to alveoli through system of air passages.
Inhaled air taken to the larynx, passes through glottis into the trachea.
Bifurcates into right and left bronchi which enter each lung and further subdivide into bronchioles that deliver air into alveoli.
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10. When air sacs are expanded during inspiration, they take in air.
Respiration in Birds
Bird lung channels air through tiny air vessels called parabronchi, where gas exchange occurs.
Uni-directional flow.
When air sacs are expanded during inspiration, they take in air.
When they are compressed during expiration, they push air into and through the lungs.
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11. Respiration in Birds Avian respiration occurs in two cycles.
Each cycle has an inspiration and an expiration phase.
Cross-current flow has the capacity to extract more oxygen from the air than a mammalian lung.
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12. Structures and Mechanisms of Breathing
The outside of each lung is covered by a visceral pleural membrane.
Second parietal pleural membrane lines inner wall of thoracic cavity.
Pleural cavity between the two membranes.
Mechanics of Breathing
Boyle’s Law - When the volume of a given quantity of gas increases, its pressure decreases.
When the pressure within the lungs is lower than the atmospheric pressure, air enters the lungs.
Thoracic volume increased by contraction of external intercostals and the diaphragm.
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13. Structures and Mechanisms of Breathing
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14. Structures and Mechanisms of Breathing
Breathing Measurements
Tidal Volume - Volume of air moving into and out of the lungs.
Vital Capacity - Maximum amount of air that can be expired after a forceful inspiration.
Hypoventilating - Slow breathing - Too much carbon dioxide.
Hyperventilating - Rapid Breathing - Not enough carbon dioxide.
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15. Mechanisms That Regulate Breathing
Rise in carbon dioxide causes blood pH to lower, stimulating neurons in the aortic and carotid bodies to send impulses to the control center in the medulla oblongata.
Sends impulses to diaphragm and external intercostal muscles, stimulating them to contract, expanding chest cavity.
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16. Hemoglobin and Oxygen Transport
Hemoglobin is a protein composed of four polypeptide chains and four organic heme groups.
Iron atom at center of each heme group.
Hemoglobin loads up with oxygen in the lungs, forming oxyhemoglobin.
As blood passes through the capillaries, some of the oxyhemoglobin releases oxygen and become deoxyhemoglobin.
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17. Hemoglobin and Oxygen Transport
Oxygen transport in the blood is affected by many conditions.
pH - Bohr’s Effect.
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18. Carbon Dioxide and Nitric Oxide Transport
About 8% of CO2 in blood is dissolved in plasma and another 20% is bound to hemoglobin.
Remaining 72% of CO2 diffuses into red blood cells where carbonic anhydrase catalyzes the combination of CO2 with water to form carbonic acid.
Blood flow and blood pressure are also regulated by the amount of NO released into the bloodstream.
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19. Copyright © McGraw-Hill Companies Permission required for reproduction or display
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