Ch49_Lecture_Spr11

Ch49_Lecture_Spr11 - 4 28 49 Gas Exchange in Animals 49 Gas...

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Gas Exchange in Animals 49
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49 Gas Exchange in Animals • 49.1 What Physical Factors Govern Respiratory Gas Exchange? • 49.2 What Adaptations Maximize Respiratory Gas Exchange? • 49.3 How Do Human Lungs Work? • 49.4 How Does Blood Transport Respiratory Gases? • 49.5 How Is Breathing Regulated?
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49.1 What Physical Factors Govern Respiratory Gas Exchange? Gas exchange systems are made up of surfaces and the mechanisms that ventilate and perfuse those surfaces Ventilation is ambient fluid (water or air) flowing past exterior of exchange surface Perfusion is circulatory fluid (blood, hemolymph) flowing inside exchange surface http://www.pnas.org/content/99/16/10411/F1.small.gif
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49.1 What Physical Factors Govern Respiratory Gas Exchange? O 2 and CO 2 are respiratory gases exchanged by diffusion along their concentration gradients Partial pressure is concentration of a gas in a mixture Barometric pressure – atmospheric pressure at sea level is 760 mm Hg Partial pressure of O 2 (P O 2 ) is 159 mm Hg or 20.9% of atmosphere www.allstar.fiu.edu/aero/images
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49.1 What Physical Factors Govern Respiratory Gas Exchange? Fick’s law of diffusion applies to all gas exchange systems: Q : rate of diffusion D : diffusion coefficient — characteristic of diffusing substance, medium, and temperature Q = DA P 1 P 2 L
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49.1 What Physical Factors Govern Respiratory Gas Exchange? A : surface area where diffusion occurs P 1 and P 2 : partial pressures of gas at two locations L : path length between locations (P 1 – P 2 )/L is partial pressure gradient sets how fast gases diffuse Q = DA P 1 P 2 L
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49.1 What Physical Factors Govern Respiratory Gas Exchange? Oxygen is easier to obtain from air than from water: O 2 content of air is higher than water O 2 diffuses much faster through air Air and water must be moved by animal over its gas exchange surfaces to obtain O 2 it requires more energy to move denser/more viscous water across membranes than air
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49.1 What Physical Factors Govern Respiratory Gas Exchange? O 2 diffusion is slow even cells with low metabolism must be only 1–2 mm from O 2 source limits size and shape of species without internal systems for gas exchange these species have evolved larger surface areas central cavities, or specialized respiratory systems
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Figure 49.1 Keeping in Touch with the Medium
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49.1 What Physical Factors Govern Respiratory Gas Exchange? An aquatic animal’s body temperature and metabolic rate rise with an increase in water temperature Dilemma : need for O 2 increases while available O 2 decreases in warmer water Increase in altitude reduces available O 2 for air breathers due to lower partial pressure of O 2 at high altitudes www.as.ua.edu/ant/bindon/ant475/altitude
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Figure 49.2 The Double Bind of Water Breathers
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Respiratory gas exchange is a two-way process: CO 2 diffuses out of body as O 2 diffuses in Concentration gradient of CO 2 from air-breathers to environment is always large Partial pressure of CO 2 in air is
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Ch49_Lecture_Spr11 - 4 28 49 Gas Exchange in Animals 49 Gas...

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