Please enable JavaScript.

Coggle requires JavaScript to display documents.

Respiratory System (Pulmonary Ventilation (Mechanisms (Boyle's Law:…

- - - - P1 x V1=P2 x V2
      - Pressure varies inversely with volume
    - - Inspiration: Lung volume increases -> Pressure decreases
      - Expiration: Lung volume decreases -> Pressure increases
    - - Inspiration: chest wall expands -> pressure more negative
      - Expiration: chest wall recoils -> pressure returns to initial value (less negative)
    - - Minute ventilation (L/min)
        
        Rough estimate of effectiveness
        
        Define: amount of gas that flows into or out of respiratory tract in 1 min
        
        = Tidal volume (ml) x Respiratory rate (/min)
      - Alveolar ventilation rate (ml/min)
        
        Better indicator
        
        Define: amount of gas that flows into or out of alveoli in a particular time
        
        = frequency (breaths/min) x (Tidal volume - dead space) (ml/breath)
        
        Dead space (usually alveolar dead space): constant, AVR usually affected by TV rather than frequency
        
        Total Dead Space: sum of anatomical and alveolar dead space
        
        Anatomical: air remains in passageways -> not contribute to gas exchange
        
        Alveolar: occupied by non-functional alveoli due to collapse or obstruction
  - - - Vital Capacity (VC): Sum of TV+IRV+ERV
      - Inspiratory Capacity (IC):Sum of TV+IRV
      - Total Lung Capacity (TLC): Sum of all lung volumes (TV+IRV+ERV+RV)
      - Functional Residual Capacity (FRC): Sum of RV+ERV
- - - - CO2 diffuses from the blood to the lungs
      - O2 diffuses from the lungs to the blood
  - - - Thickness and Surface area of Respiratory Membrane: The greater the surface area of the respiratory membrane, the more gas can diffuse across it
      - Partial Pressure Gradients and Gas Solubilities: Steep partial pressure gradient for O2 exists between blood and lungs; Partial pressure gradient for CO2 is less steep, but diffuses in equal amounts with O2 because CO2 is 20x more soluble in plasma and alveolar fluid than O2
        
        Dalton's Law of Partial Pressures: Total pressure exerted by mixture of gases is equal to sum of pressures exerted by each gas; partial pressures of each gas is directly proportional to the percentage of that gas in the gas mixture; At high altitudes, partial pressures decline, while at lower altitudes (under water), partial pressures increase significantly
        
        Henry's Law: states that when a gas is in contact with a liquid, the gas will dissolve in the liquid in proportion to its partial pressure; the greater the concentration of a particular gas in the gas phase, the more and the faster the gas will move into the liquid. At equilibrium, partial pressures in the two phases will be equal. The amount of each gas that will dissolve depends on solubility of the gas in liquid and the temperature of the liquid; CO2 is 20x more soluble in water than O2 and little N2 will dissolve; solubility decreases as temperature of liquid rises
      - Ventilation-Perfusion Coupling: alveolar ventilation and pulmonary blood perfusion rates must be matched for optimal, efficient gas exchange
- - - - Dissolved CO2 is bound and carried in the RBCs as carbaminohemoglobin. (CO2+Hb⇌HbCO2) This reaction is rapid and does not require a catalyst. Carbon dioxide binds to amino acids of globin. Carbon dioxide rapidly dissociates from hemoglobin in the lungs, where the PCO2 of alveolar air is lower than that in blood. Carbon dioxide readily binds with hemoglobin in the tissues, where the PCO2 is higher than that in blood. Deoxygenated hemoglobin combines more readily with carbon dioxide than does oxygenated hemoglobin.
    - - Most carbon dioxide molecules entering the plasma quickly enter RBCs. The reactions that convert carbon dioxide to bicarbonate ions for transport mostly occur inside RBCs. CO2+H2O⇌H2CO3 (carbonicacid)⇌H+ +HCO3−(bicarbonate ion). Although this reaction also occurs in plasma, it is thousands of times faster in RBCs because they contain carbonic anhydrase, an enzyme that reversibly catalyzes the conversion of carbon dioxide and water to carbonic acid. Hydrogen ions released during the reaction (as well as CO2 itself) bind to Hb, triggering the Bohr effect. In this way CO2 loading enhances O2 release. Once generated, HCO3− moves quickly from the RBCs into the plasma, where it is carried to the lungs. To counterbalance the rapid outrush of these anions from the RBCs, chloride ions move from the plasma into the RBCs. This ion exchange process, called the chloride shift, occurs via facilitated diffusion through an RBC membrane protein.
      - The Haldane effect: reflects the greater ability of reduced hemoglobin to form carbaminohemoglobin and to buffer H+ by combining with it. The lower the PO2 and the lower the Hb saturation with oxygen, the more CO2 that blood can carry.
      - Comparing the Haldane and Bohr effects: As CO2 enters the systemic bloodstream, it causes more oxygen to dissociate from Hb (Bohr effect). The dissociation of O2 allows more CO2 to combine with Hb (Haldane effect).
      - The bicarbonate buffer system resists shifts in blood pH. If the hydrogen ion concentration in blood begins to rise, excess H+ is removed by combining with HCO3− to form carbonic acid (a weak acid). If H+ concentration in blood drops below desirable levels, carbonic acid dissociates, releasing hydrogen ions and lowering the pH again.
  - - - Each hemoglobin molecule can combine with 4 molecules of O2 (each oxygen can bin to one heme group). This is called oxyhemoglobin. Hemoglobin that has released oxygen for the cells to use is called deoxyhemoglobin.
        
        Rate at which Hb reversibly binds or releases O2 is reulated by PO2, temprature, blood pH, PCO2, and BPG concentration. All factors modify hemoglobin's 3D structure.
        
        When factors are decreased: When more oxygen is available (pulmonary capillaries), it will want to bind to hemoglobin. When one O2 molecule saturates a heme group, the hemoglobin molecules's affinity for other O2 molecules to bind increases.
        
        When factors are increased: All of these factors tend to be highest in the systemic capillaries, where oxygen unloading is the goal. As cells metabolize glucose and use O2, they release CO2, which increases the PCO2 and H+ levels in capillary blood. Both declining blood pH (acidosis) and increasing PCO2 weaken the Hb-O2 bond This is called the Bohr effect, it enhances oxygen unloading where it is most needed.
- - - - Chemoreceptors: sensors that respond to chemical fluctuations. Among the factors that influence breathing rate and depth, the most important are changing levels of CO2, O2, and H+ in arterial blood.
- - - - Oxygen moves from blood to tissues because tissue PO2 is always lower than in arterial blood PO2 (40 vs. 100 mm Hg)
      - CO2 moves from tissues into blood because tissue PCO2 is always higher than arterial blood PCO2 (45 vs. 40mm Hg)
      - Venous blood returning to the heart has PO2 of 40 mm Hg and PCO2 of 45 mm Hg
    - - Molecular O2 is cariied in blood in 2 ways. 1.5% is dissolved in plasma and 98.5% is looslely bound to each Fe of hemoglobin (Hb) in RBCs. Each Hb can transport 4 O2 molecules.
        
        Oxygen-Hemoglobin Dissociation Curve: Percent of Hb saturation can be plotted against PO2 concentrations. The graph is an S shaped curve. Increases in temperature, H+, and PCO2 shift curve to the right. Decreases in same factors shift curve left.