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Respiratory System (Pulmonary Ventilation (Breathing) (Major Regions (Dead…

- - - - intra pleural pressure: pressure within pleural cavity; always negative to act as suction with lungs
      - transpulmonary pressure: difference between the intrapleural and intrapulmonary pressures
        creates the suction to keep the lungs inflated
        *when there is no pressure difference there is no suction and the lung collapses
      - intrapulmonary pressure: pressure within lungs
  - - - Total Dead Space: sum of anatomical and alveolar dead space
      - Anatomical: air that remains in passageways (conducting zone)
        does NOT contribute to gas exchange
      - Minute Ventilation: amount of gas that flows into/out of respiratory tract in 1 minute
        **does NOT take dead space into account
      - Alveolar Ventilation: flow of gases into/out of alveoli during particular time
        **DOES take dead space into account
        AVR = Resp Rate x (TV - dead space)
        (ml/min) (breaths/min) (ml/breath)
      - Alveolar: space occupied by non functional alveoli
        
        caused by collapse or destruction (emphysema)
  - - - Inspiratory Reserve Volume (IRV)
        
        Amt air that can be inspired forcibly beyond TV
      - Expiratory Reserve Volume (ERV)
        
        amt air that can be forcibly expelled from lungs
      - Tidal Volume (TV)
        
        Amt air moved in/out of lungs with each (normal) breath
      - Residual Volume (RV)
        
        amt air always in lungs, needed to keep alveoli open
    - - functional residual capacity (FRC)
        
        amt air TYPICALLY staying in lungs (normal breathing)
        FRC = RV + ERV
      - vital capacity (VC)
        
        amt of air we move through lungs
        VC = TV + IRV + ERV
      - Inspiratory Capacity (IC)
        
        total amt we can take into lungs
        IC = TV + IRV
      - total lung capacity (TLC)
        
        total amt air lungs can hold
        TLC = TV + IRV + ERV + RV
- - - - Partial pressure gradients and gas solubilities
        
        Partial pressure gradients of O2 and CO2 drive the diffusion of these gases across the respiratory membrane. O2 rapidly diffuses from the alveoli into the pulmonary capillary blood because PO2 is 104 mm Hg in the alveoli and 40 mm Hg in the pulmonary arteries.
        
        CO2 diffuses in the opposite direction, but the pressure difference isn't as great (5 mm Hg vs. 40 mm Hg). Expiration gradually expels CO2 from the alveoli but at an equal amount as O2 is being diffused because CO2 is more soluble in plasma and alveolar fluid that O2.
        
        Dalton's Law of Partial Pressure: Total pressure exerted by mixture of gases is equal to sum of pressures exerted by each gas
        Partial pressure: Pressure exerted by each gas in mixture;
        directly proportional to its percentage in mixture
      - Thickness and surface area of the respiratory membranes
        
        Gas exchange is so efficient because of how thin the respiratory membrane is and how large the surface area is for the most efficient diffusion.
      - Ventilation-perfusion coupling (matching alveolar ventilation with pulmonary blood perfusion)
        
        For optimal gas exchange, the ventilation (amount of gas reaching the alveoli) and perfusion (the blood flow in pulmonary capillaries) should be very close.
        
        PO2 controls perfusion by changing arteriole diameter.
        
        PCO2 controls ventilation by bronchiolar diameter
        
        If alveolar ventilation is inadequate, PO2 is low which will make the terminal arterioles constrict so that blood will be redirected to areas where PO2 are higher. If alveoli ventilation is maximal, and PO2 is higher, pulmonary arterioles dilate and blood flow into the capillary increases. For PCO2: Bronchioles dilate where CO2 levels are high to allow for CO2 to leave body quicker. When CO2 levels are low, bronchioles constrict.
- - - - when H+ concentration increases: excess is removed by combining H+ with bicarbonate to form carbonic acid, which is then broken down to carbon dioxide and water to lower pH
      - when H+ concentration decreases: carbon dioxide and water combine to form carbonic acid, which is converted to H+ and bicarbonate to increase pH
- - - - How is CO2 transported?
        
        7-10% dissolved in plasma as PCO2
        
        20% transported as carbaminohemoglobin
        
        70% transported as bicarbonate ions in plasma
      - How is O2 transported?
        
        1.5% is dissolved in plasma
        
        98.5% is loosely bound to each heme group of hemoglobin in RBC's
      - What affects internal respiration?
        
        Gas solubility
        
        Henry's Law: For gas mixtures in contact with liquids
        
        Each gas will dissolve in the liquid in proportion to its partial pressure
        
        At equilibrium, partial pressures in the two phases will be equal
        
        Amount of each gas that will dissolve depends on:
        
        Solubility:CO2is 20 ×more soluble in water than O2, and little N2 will dissolve
        Temperature: as temperature of liquid rises, solubility decreases
        
        partial pressure of O2 and CO2
        
        Partial pressure of O2 in blood: 100mm Hg
        Partial pressure in tissues: 40 mm Hg
        
        Partial pressure of CO2 in blood: 40 mm Hg
        Partial pressure of CO2 in tissues: 45 mm Hg
        
        Gases move from areas of high concentration to low concentration so CO2 wants to diffuse into the blood and O2 wants to diffuse into tissues
    - - amount of CO2 transported is affected by PO2
      - the lower the PO2, the more CO2 can bind to hemoglobin and form carbaminohemoglobin
    - - At tissues, as more CO2 enter blood, more O2 dissociates from hemoglobin, more CO2 can bind to hemoglobin and form carbaminohemoglobin