TAILIEUCHUNG - Ebook Guyton and hall textbook of medical physiology (12/E): Part 2

(BQ) Part 2 book "Guyton and hall textbook of medical physiology" has contents: Respiration; aviation, space, and deep sea diving physiology; gastrointestinal physiology; metabolism and temperature regulation; sports physiology, and other contents. | Aviation, Space, and Deep-Sea Diving Physiology 43. Aviation, High Altitude, and Space Physiology 44. Physiology of Deep-Sea Diving and Other Hyperbaric Conditions Unit vIII This page intentionally left blank chapter 43 As humans have ascended to higher and higher ­altitudes in aviation, mountain climbing, and space vehicles, it has become progressively more important to understand the effects of altitude and low gas pressures on the human body. This chapter deals with these problems, as well as acceleratory forces, weightlessness, and other challenges to body homeostasis that occur at high altitude and in space flight. Effects of Low Oxygen Pressure on the Body Barometric Pressures at Different Altitudes.  Table 43-1 gives the approximate barometric and oxygen pressures at different altitudes, showing that at sea level, the barometric pressure is 760 mm Hg; at 10,000 feet, only 523 mm Hg; and at 50,000 feet, 87 mm Hg. This decrease in barometric pressure is the basic cause of all the hypoxia problems in high-altitude physiology because, as the barometric pressure decreases, the atmospheric oxygen partial pressure (Po2) decreases proportionately, remaining at all times slightly less than 21 percent of the total barometric pressure; at sea level Po2 is about 159 mm Hg, but at 50,000 feet Po2 is only 18 mm Hg. Alveolar Po2 at Different Elevations Carbon Dioxide and Water Vapor Decrease the Alveolar Oxygen.  Even at high altitudes, carbon dioxide is continually excreted from the pulmonary blood into the alveoli. Also, water vaporizes into the inspired air from the respiratory surfaces. These two gases dilute the oxygen in the alveoli, thus reducing the oxygen concentration. Water vapor pressure in the alveoli remains at 47 mm Hg as long as the body temperature is normal, regardless of altitude. In the case of carbon dioxide, during exposure to very high altitudes, the alveolar Pco2 falls from the sealevel value of 40 mm Hg to lower values. In the .

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• Published financial statements
• Deep sea diving physiology
• Gastrointestinal physiology
• Temperature regulation
• Sports physiology
• Current liabilities
• Ownership interest
• Current assets
• Ratio analysis
• Financial accounting
• Texbook of medical physiology
• Medical physiology
• The nervous system
• Guyton and hall physiology review
• The special senses
• Exercise Physiology
• Nutrition
• Neurotransmitters
• Amino Acids
• Glycogen Stores