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Respiration CD Worksheet #2 Pulmonary Ventilation Graphics are used with permission of A.D.A.M.® Software, Inc. and Benjamin/Cummings Publishing Co. Introduction • Pulmonary ventilation, or breathing, is the exchange of air between the atmosphere and the lungs. • As air moves into and out of the lungs, it travels from regions of high air pressure to regions of low air pressure Goals • To relate Boyle's law to ventilation. • To identify the muscles used during ventilation. • To understand how volume changes in the thoracic cavity cause pressure changes that lead to breathing. • To identify factors which influence airway resistance and lung compliance. Study Questions: 1. What is another term for pulmonary ventilation? Breathing 2. Define pulmonary ventilation in simple terms. The exchange of air between the atmosphere and the lungs 3. What causes pressure within a gas sample? Pressure is caused by gas molecules striking the walls of a container 4. Define Boyle's Law. The pressure of a gas is inversely proportional to the volume of its container 5. a. What happens to the pressure of a gas if you increase the size of a container? b. What happens to the pressure of a gas if you decrease the size of a container? a. Pressure decreases. b. Pressure increases 6. How is the volume of the thoracic cavity changed? By muscle contraction and relaxation. 7. What two muscles contract during quiet inspiration? What is the effect of their contraction? The diaphragm and the external intercostals. As a result the thoracic cavity enlarges in all dimensions 8. What happens to pressure when we increase the volume within the thoracic cavity and the lungs? Pressure decreases. 9. a. What happens to the diaphragm muscle when it contracts? b. What happens to the external intercostal muscles when they contract? . a. The diaphragm flattens and moves inferiorly. b. The external intercostal muscles elevate the rib cage and move the sternum anteriorly 10. Explain what happens in quiet expiration. The diaphragm and the external intercostal muscles relax, and the elastic lungs and thoracic wall recoil inward 11. What effect does quiet expiration have on the volume of the thoracic cavity? How does this effect the pressure within the cavity? The volume is decreased and therefore the pressure increases within the thoracic cavity 12. Which of these are active and which are passive processes? active: a,c,d passive: b a. quiet inspiration b. quiet expiration c. deep inspiration d. forceful expiration 13. What is the pressure within the lungs called? . Intrapulmonary, or intra-alveolar, pressure. 14. What is a typical value for intrapulmonary, or intra-alveolar, pressure during normal breathing at these times. Assume the atmospheric pressure is 760 mm Hg. a. 760 mm Hg b. 759 mm Hg c. 760 mm Hg d. 761 mm Hg a. before inspiration b. during inspiration c. after inspiration and before expiration d. during expiration 15. When discussing respiratory pressures, what do these pressures mean? a. 0 b. -1 c. +1 a. atmospheric pressure b. 1 mm Hg below atmospheric pressure c. 1 mm Hg above atmospheric pressure 16. What is the value of intrapleural pressure compared to intrapulmonary (alveolar) pressure? Intrapleural pressure is always less than intrapulmonary (alveolar) pressure. 17. What three factors cause the intrapleural pressure to be less than intrapulmonary (alveolar) pressure? (1) The surface tension of the alveolar fluid. (2) The elasticity of the lungs. (3) The elasticity of the thoracic wall. 18. How do each of the following decrease the pressure inside the pleural cavity: a. the surface tension of the alveolar fluid b. The elasticity of the lungs. c. The elasticity of the thoracic wall. . a. The surface tension of the alveolar fluid tends to pull each of the alveoli inward and therefore pulls the entire lung inward. This force acts to increase the volume of intrapleural cavity, therefore decreasing its pressure. b. The elastic tissue in the lungs tends to recoil and pull the lung inward. As the lung moves away from the thoracic wall, the cavity becomes slightly larger. This force acts to increase the volume of intrapleural cavity, therefore decreasing its pressure. c. The elastic thoracic wall tends to pull away from the lung. This force also acts to increase the volume of intrapleural cavity, therefore decreasing its pressure. 19. What happens to the volume of the pleural cavity and the intrapleural pressure during a. inspiration? The volume of the pleural cavity increases, decreasing intrapleural pressure b. expiration? The volume of the pleural cavity decreases, increasing the intrapleural pressure 20. Why does a lung collapse if you cut into the pleural cavity? . Because the pressure of the intrapleural cavity becomes equal to atmospheric pressure. There is no longer less pressure in the intrapleural cavity compared to within the alveoli so the lung collapses. 21. a. What is the transpulmonary pressure? b. What is the function of the transpulmonary pressure? a. The difference between the intrapleural and intrapulmonary pressures. b. It creates the suction to keep the lungs inflated. 22. If a pneumothorax occurs in one lung, why doesn't it also occur in the other lung? . Each lung has its own pleural cavity and pleural membranes so that changes in the intrapleural pressure of one lung do not affect the other lung. 23. Match the pressures to their definition: a. Intrapleural Pressure b. Intrapulmonary Pressure c. Transpulmonary Pressure • Intrapulmonary Pressure a. The pressure within the pleural cavity. • Transpulmonary Pressure b. The pressure within the • Intrapleural Pressure alveoli. c. The difference between the pressure within the pleural cavity and the pressure within the alveoli. 24. What is the tidal volume? The volume of air which enters and leaves the lungs during quiet breathing 25. Chose the proper words to explain what happens during inspiration. The diaphragm and external intercostal muscles __________ (contract, relax). contract
The volume of the thoracic cavity _________ (increases, decreases). increases
Intrapleural pressure becomes ________ (more, less) negative. more
Lungs ________ (recoil, expand). expand
Intrapulmonary pressure __________ (increases, decreases). decreases
Air flows _________ (into, out of) the lungs. into 26. Chose the proper words to explain what happens during expiration. The diaphragm and external intercostal muscles __________ (contract, relax). relax
The volume of the thoracic cavity _________ (increases, decreases). decreases
Intrapleural pressure becomes ________ (more, less) negative. less
Lungs ________ (recoil, expand). recoil
Intrapulmonary pressure __________ (increases, decreases). increases
Air flows _________ (into, out of) the lungs. out of 27. What two factors play roles in ventilation besides muscle contraction? (1) The resistance within the airways (2) Lung compliance 28. What is airway resistance due to? The gas molecules encountering resistance as they strike the walls of the airway 29. What happens to the airway resistance as the bronchiole constricts? As the diameter of the walls of the bronchiole decrease, the resistance increases 30. 31. 32. 33. 34.
Does histamine constrict or dilate bronchioles? Constrict Does epinephrine constrict or dilate bronchioles? Dilates What term is used to describe the ease with which the lungs expand? Lung compliance What two factors is lung compliance dependent upon? (1) The stretchability of the elastic fibers within the lungs. (2) The surface tension within the alveoli. What happens to alveoli when there is not enough surfactant? Alveoli have high surface tension, and they tend to collapse Summary • Muscle activity causes changes in the volume of the thoracic cavity during breathing. • Changing the thoracic cavity volume causes intrapulmonary and intrapleural pressure changes, which allow air to move from high pressure to low pressure regions. • Airway resistance is normally low, but nervous stimulation and chemical factors can change the diameter of bronchioles, thereby altering resistance and airflow. • Lung compliance is normally high due to the lung's abundant elastic tissue and surfactant's ability to lower the surface tension of the alveolar fluid.