TopicRevRespW11

TopicRevRespW11 - January 22, 2011 1 2 3 4 5 ...

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Unformatted text preview: January 22, 2011 1. 2. 3. 4. 5. NPB101  ­ W11 TOPICAL REVIEW RESPIRATION Page 1 of 2 Know the respiratory volumes and capacities, particularly tidal volume and functional residual capacity. It is important that you understand the functional role of FRC as a reservoir for oxygen and buffer volume for carbon dioxide during tidal, phasic ventilation. What would happen to alveolar and pulmonary capillary partial pressure for oxygen during inspiration and expiration in the absence of a functional residual capacity, e.g. the alveoli would fill only with outside air during inspiration and empty of air during expiration? Understand the relationship between the intrinsic forces of the lung and chest wall in determining intrapleural pressure at FRC. (Concept: A wall only moves in or out when there is a net force acting on the wall. Lung volume only changes if there if there is a net force acting across the lung. If the lung volume is not changing, there is no net force acting on the lung. Therefore, the transmural pressure for the lung and chest wall must be equal in magnitude and opposite in direction to the intrinsic forces of the lung. The same relationship between the intrinsic forces and transmural pressure applies to the chest wall.) Know the role of surface tension in determining one of the intrinsic forces acting on the lung. Understand the definitions of transmural pressure. Understand the sequence of changes in the relationship between pleural pressure and the instrinsic forces of the lung or initiating inspiration, the end of inspiration, the initiation of expiration and termination of expiration at FRC.. Understand how changes in thoracic volume produce changes in pleural pressure which in turn produce changes in the transmural pressure for the lung leading to changes in lung volume. Understand the relationship between Palv, transmural pressure, and the intrinsic forces of the lung at FRC, during inspiration, at end of inspiration, and during expiration. If I give you magnitudes of pressures and forces for the lung, Palv, and the pleural space be able to determine if the lung will remain at its volume, expand or decrease its volume. Know the relationship between dead space ventilation and alveolar ventilation in determining alveolar Po2 and Pco2. Understand the interaction between ventilation and blood flow (perfusion) in determining alveolar gas composition and the partial pressure of gases in the blood leaving the pulmonary capillaries and entering the pulmonary veins. (Concept: Blood leaving the pulmonary capillaries and entering the pulmonary veins equilibrates in partial pressure with the gas in the alveolar air.) Understand the concept of the interaction between the rate of gas delivery to and rate gas removal from the alveoli on alveolar and pulmonary capillary/pulmonary venous gas composition. (Concept: Alveolar ventilation supplies oxygen and removes carbon dioxide. Blood flow (through tissue metabolism) to the alveoli removes oxygen and supplies carbon dioxide.) Understand that alveolar partial pressures for oxygen and carbon dioxide represent the equilibrium established between the rate of gas delivery and the rate of gas removal. Understand why alveolar Po2 is not the same as ambient, outside air. Understand why alveolar Pco2 isn’t the same as outside air or the same as pulmonary arterial/systemic venous blood. What would happen to alveolar Po2 and Pco2 if there is an increase in alveolar ventilation? What would happen to alveolar and pulmonary capillary/pulmonary venous Po2 and Pco2 if there was a change in metabolism but no change in ventilation? If there is an increase in partial pressure of oxygen in the alveolar air with no change in metabolism, will oxygen uptake/utilization increase? (Do changes in the partial pressure of pulmonary capillary and systemic arterial blood change oxygen utilization by the tissues?) If there were an increase in alveolar ventilation with no change in metabolism what would you predict will happen to systemic arterial Po2 and systemic arterial Pco2? What would happen to systemic venous Po2 and Pco2? What is the relationship between partial pressure of a gas and its content in air ?(Concept: the partial pressure of gas in air defines the content of gas in air.) How do the interactions among the quantity of free gas, gas that is dissolved, and that which is chemically combined/reacted with elements in blood or in another medium determine the total gas content within the blood or medium? If you are comparing two gases in the same or different mediums, can you explicitly determine gas content for TopicRevRespW11.docx January 22, 2011 NPB101  ­ W11 TOPICAL REVIEW RESPIRATION Page 2 of 2 each gas from their partial pressures without knowing the properties of the gas or the properties of the medium? Why? Understand the concept of equilibrium among gas states in determining the partial pressure of the gas within a medium or blood and the content of gas in each state of the gas in the medium. What would happen to the partial pressure or the quantity of a gas in a medium if there was an increase or decrease in the ability of the gas to chemically combine when the gas cannot leave the medium? What would happen to the partial pressure of a gas and the partitioning of a gas between phases for a given quantity of gas if there was a decrease in the solubility of the gas in the medium? Would the partial pressure of the gas increase, decrease or remain unchanged? Understand why the partial pressure of carbon dioxide in arterial blood is lower than that for oxygen even though there is over 2 ½ time the quantity of carbon dioxide in blood. 6. 7. 8. 9. How are oxygen and carbon dioxide transported in the blood? What are the relative proportions that are dissolved and chemically combined for each gas? What is the major mode or form in which carbon dioxide is carried in the blood? What would have to happen to your cardiac output required to meet your normal resting oxygen needs if there was no hemoglobin? Why? Would the transport of carbon dioxide and oxygen be affected equally in the absence of hemoglobin? Why (Think about how much oxygen is carried by hemoglobin and how much carbon dioxide is carried by hemoglobin)? Be able to draw/visualize the oxyhemoglobin dissociation curve and be aware of the X axis and Y axis scales. Understand the relationship between oxygen partial pressure and oxygen content for the oxyhemoglobin dissociation curve. What are the affects of changes in Pco2, H+, bis ­phosphoglycerate (same as DPG), and temperature on the oxyhemoglobin dissociation curve? What happens to the position of the curve, the partial pressure of oxygen, and oxygen content at the lung and why? What happens to the position of the curve, the partial pressure of oxygen, and oxygen content at the tissues and why? Understand how changes in Po2 over different regions of the curve affect oxygen content and why. Also understand how equal changes in content over different regions of the curve affect the partial pressure of oxygen and why, e.g. a decrease in content from 20 to 18 ml O2/100 ml blood produces a much larger decrease in Po2 for oxygen than a corresponding decrease in content from 10 to 8 ml O2/100 ml of blood. Recognize that the magnitude of change in the partial pressure for oxygen for a change in content changes more if all the change occurs through that dissolved versus a change that involves both oxygen combined with hemoglobin and that dissolved (the buffering of a change in partial pressure of oxygen when hemoglobin either takes up or gives up oxygen.). Be able to work with the oxyhemoglobin dissociation curve in determining the affects of changes in the partial pressure of oxygen over different ranges on oxygen content within the blood. Be able to work with the oxyhemoglobin dissociation curve to determine changes in the partial pressure of oxygen with changes in oxygen content of the blood over different ranges of blood oxygen content. Understand the chemoreceptive reflexes. What is sensed and where is each sensed? Recognize that changes in Po2 are sensed through the peripheral chemoreceptors while changes in Pco2 and H+ are sensed through the central chemoreceptors. Is there greater sensitivity of the general chemoreceptor population (central and peripheral) to changes in Po2 or changes in Pco2/H+? What is the effective intracellular stimulus to changes in Pco2 and H+? How do the two populations of central chemoreceptors respond to changes in blood Pco2 and H+? Would both respond to changes in Pco2? Why? Would both respond to changes in H+ or pH with no change in Pco2? Why? Reflexes from the lung. (Effective stimuli, receptors, afferent, central integration and efferent responses) What is the affect of the Hering ­Breuer Reflex (inspirato ­inhibitory reflex) on tidal volume? If the vagi/parasympathetic afferent nerves coming from the lung are cut, what will happen to tidal volume and breathing frequency? Understand central control of respiration. Where is the basic breathing rhythm generated? Understand the roles of the hypothalamus and higher brain regions on ventilation. TopicRevRespW11.docx ...
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This note was uploaded on 08/21/2011 for the course NPB 101 taught by Professor Fuller,charles/goldberg,jack during the Winter '08 term at UC Davis.

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