Chapter 17 Summary - Respiratory System PDF

530 CHAPTER 17 The Respiratory System: Gas Exchange and Regulation of Breathing CHAPTER REVIEW SUMMARY 17.1 Overview of the Pulmonary Circulation, p. 504 • To maintain relatively constant levels of • • • • • • oxygen in the systemic arterial blood, inspired oxygen moves from alveolar air...

530 CHAPTER 17 The Respiratory System: Gas Exchange and Regulation of Breathing CHAPTER REVIEW SUMMARY 17.1 Overview of the Pulmonary Circulation, p. 504 • To maintain relatively constant levels of • • • • • • oxygen in the systemic arterial blood, inspired oxygen moves from alveolar air into the blood at the same rate it is consumed by the tissues, just as carbon dioxide moves into alveolar air from the blood at the same rate it is produced by the tissues. The respiratory quotient is the ratio of the amount of carbon dioxide produced by the body to the amount of oxygen consumed. The right heart pumps deoxygenated blood to the pulmonary capillaries, where oxygen diffuses from the alveoli to blood, and carbon dioxide diffuses from blood to the alveoli. The respiratory membrane provides a large surface area and short distance for diffusion, so the diffusion rates are rapid. Once oxygenated in the lungs, blood returns to the left side of the heart, where it is pumped to the systemic capillaries in the tissues of the body. Oxygen diffuses from the blood to tissue, and carbon dioxide diffuses from tissue to the blood. After becoming deoxygenated, blood returns to the right side of the heart. Copyright © 2017. Pearson Education, Limited. All rights reserved. Respiratory, Anatomy Review: Respiratory Structures Cardiovascular, Anatomy Review: The Heart 17.3 Exchange of Oxygen and Carbon Dioxide, p. 508 • Gas exchange occurs by diffusion down partial pressure gradients. • In the lungs, oxygen diffuses from alveoli • • • • • • mixture are called partial pressures; they are equal to the fractional concentration of the gas multiplied by the total pressure. • Gases can dissolve in liquids to varying degrees based on their solubility and partial pressure. • The greater its solubility and its partial pressure, the larger the amount of a gas that dissolves in a liquid. • Neither oxygen nor carbon dioxide is very soluble in water, but carbon dioxide is approximately 20 times more soluble than oxygen. Respiratory, Gas Exchange to blood, and carbon dioxide diffuses from blood to alveoli. In respiring tissues, oxygen diffuses from blood to tissue, and carbon dioxide diffuses from tissue to blood. The amount of oxygen and carbon dioxide diffusing across a particular systemic capillary depends on the activity of the tissue; more active tissues have greater partial pressure gradients, leading to greater diffusion rates. Alveolar PO2 and PCO2 are determined by the PO2 and PCO2 of inspired air, the alveolar ventilation, and the rates of oxygen consumption and carbon dioxide production in respiring tissue. Alveolar PO2 and PCO2 determine arterial PO2 and PCO2. Normally, alveolar ventilation is matched to oxygen consumption and carbon dioxide production. Hyperpnea occurs when metabolic activity increases, causing ventilation to increase in an effort to match the oxygen demands of the tissue. • • • • 17.4 Transport of Gases in the Blood, p. 511 • Oxygen is transported in blood by being • • • • dissolved in blood (1.5%) or bound to hemoglobin (98.5%). The relationship between PO2 and the amount of oxygen bound to hemoglobin is shown in the hemoglobin-oxygen dissociation curve. Factors in blood that influence the binding of oxygen to hemoglobin include temperature, pH, PCO2, 2,3-BPG, carbon monoxide, and PO2. The Bohr effect is the decrease in the affinity of hemoglobin for oxygen that occurs when hydrogen ions bind to hemoglobin. The carbamino effect is the decrease in the affinity of hemoglobin for oxygen that occurs when carbon dioxide binds to hemoglobin. affinity of hemoglobin for hydrogen ions and carbon dioxide that occurs when oxygen binds to hemoglobin. Carbon dioxide is transported in blood in three ways: dissolved in blood (5–6%), bound to hemoglobin (5–8%), or dissolved in blood as bicarbonate ions (86–90%). The conversion of carbon dioxide to bicarbonate plays a significant role in maintaining acid-base balance in the blood; bicarbonate is the main form in which carbon dioxide is transported between tissues and lungs. Carbonic anhydrase catalyzes the reversible reaction that converts carbon dioxide and water to carbonic acid, which then dissociates to hydrogen ions and bicarbonate. The chloride shift is the movement of chloride ions into erythrocytes and bicarbonate into plasma; the reverse chloride shift occurs when bicarbonate ions are transported from plasma into erythrocytes in exchange for chloride ions. Respiratory, Gas Transport 17.5 Central Regulation of Ventilation, p. 519 • Breathing is a rhythmic process that is Respiratory, Gas Exchange 17.2 Diffusion of Gases, p. 506 • The pressures of individual gases in a • The Haldane effect is the decrease in the • • • • • caused by cyclical neural excitation of respiratory muscles. The generation of the breathing rhythm requires the action of respiratory centers in the brainstem. The medullary respiratory control center includes the dorsal respiratory group and the ventral respiratory group. Inspiratory neurons in these regions activate the motor neurons that innervate the inspiratory muscles, causing inspiration. The pontine respiratory group may be involved in the transition between inspiration and expiration. Higher brain areas can influence respiration. Various stimuli affect ventilation, including changes in arterial PO2 and PCO2 , stretch of the lungs, irritants in the airways, proprioceptors, arterial baroreceptors, nociceptors, thermoreceptors, emotions, and voluntary controls. Respiratory, Control of Respiration Stanfield, Cindy. Principles of Human Physiology, Global Edition, Pearson Education, Limited, 2017. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/mqu/detail.action?docID=5187887. Created from mqu on 2023-08-25 02:09:28. CHAPTER 17 17.6 Control of Ventilation by Chemoreceptors, p. 522 The Respiratory System: Gas Exchange and Regulation of Breathing 17.7 Local Regulation of Ventilation and Perfusion, p. 525 • Peripheral and central chemoreceptors • The ventilation-perfusion ratio is the detect changes in PO2, PCO2, and the pH of arterial blood. • PCO2 is the primary stimulus to the central chemoreceptors, but its effects are always indirect: CO2 must first be converted to hydrogen ions (and bicarbonate). • The peripheral chemoreceptors located in the carotid bodies respond directly to changes in pH and PCO2 and to decreases in PO2 to less than 60 mm Hg. • Central chemoreceptors are located in the medulla oblongata and respond to changes in the pH of cerebrospinal fluid. ratio between air flow to the alveoli and blood flow to the capillaries supplying those alveoli. • In normal lungs, the ventilationperfusion ratio is 1. • If ventilation to a particular alveolus is decreased, perfusion will be decreased by vasoconstriction to sustain the normal ventilation-perfusion ratio. • If perfusion to a particular alveolus is decreased, then air flow will be decreased by bronchoconstriction. • • • • 17.8 The Respiratory System in AcidBase Homeostasis, p. 526 Respiratory, Control of Respiration 531 urinary systems work together to maintain normal blood pH. Acidosis is a decrease in blood pH to 7.35 or less; alkalosis is an increase in blood pH to 7.45 or greater. The primary contribution of the respiratory system to acid-base balance is the regulation of arterial PCO2. Because carbon dioxide can be converted to carbonic acid, a change in PCO2 can cause either respiratory acidosis or respiratory alkalosis. The respiratory system works in concert with the kidneys to maintain a ratio of bicarbonate to carbon dioxide of 20:1. Respiratory, Control of Respiration • The pH of blood is tightly regulated between 7.38 and 7.42. The respiratory and EXERCISES Multiple-Choice Questions Copyright © 2017. Pearson Education, Limited. All rights reserved. 1. Under steady-state conditions, the rate at which oxygen enters pulmonary capillaries from alveolar air is equal to a) The rate at which oxygen is delivered to alveoli in inspired air. b) The rate at which oxygen is carried out of the alveoli in expired air. c) The rate at which oxygen is consumed in respiring tissues. d) The rate at which carbon dioxide is produced in respiring tissues. e) The rate at which carbon dioxide leaves the pulmonary capillaries and enters alveolar air. 2. Under normal resting conditions in systemic arteries, hemoglobin is a) Approximately 98% saturated. b) Approximately 75% saturated. c) Approximately 80% saturated. d) Less than 25% saturated. 3. The effect that pH has on the hemoglobin-oxygen dissociation curve is referred to as a) The chloride shift. b) The Bohr effect. c) The Haldane effect. d) The carbamino effect. 4. Which of the following does not affect alveolar PO2? a) The rate of oxygen consumption by respiring tissues b) Alveolar ventilation c) The PO2 of inspired air d) The volume of air contained in the alveoli e) The humidification of air as it moves through the conducting zone 5. Which of the following conditions is caused when blood PCO2decreases below normal levels? a) hypocapnia b) hyperventilation c) hypoventilation d) hypoxia e) hypercapnia 6. The oxygen saturation level of hemoglobin will increase if a) the arterial PCO2 increases b) the level of 2,3-BPG increases c) the temperature increases d) the arterial pH decreases e) the arterial PO2 increases 7. Suppose that alveolar PO2 = 100 mm Hg and PCO2 = 60 mm Hg. Which of the following is true? a) pH will be less than normal. b) Percent saturation of hemoglobin by oxygen will be less than normal. c) Bicarbonate concentration will be greater than normal. d) Both a and c are true. e) All of the above are true. 8. During alveolar gas exchange, the partial pressure of CO2 in blood a) Increases from 40 to 46 mm Hg. b) Decreases from 100 to 46 mm Hg. c) Decreases from 46 to 40 mm Hg. d) Increases from 40 to 100 mm Hg. 9. A rise in arterial PCO2 triggers an increase in ventilation by stimulating both central and peripheral chemoreceptors. The response of central chemoreceptors is due to a) Diffusion of carbon dioxide into brain extracellular fluid, which stimulates chemoreceptors directly. b) Diffusion of hydrogen ions into brain extracellular fluid, which stimulates chemoreceptors directly. c) Diffusion of carbon dioxide into brain extracellular fluid, which reacts with water to form hydrogen ions, which stimulate chemoreceptors directly. d) Diffusion of carbon dioxide into brain extracellular fluid, which reacts with water to form bicarbonate ions, which stimulate chemoreceptors directly. e) Direct stimulation by hydrogen ions in arterial blood. Stanfield, Cindy. Principles of Human Physiology, Global Edition, Pearson Education, Limited, 2017. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/mqu/detail.action?docID=5187887. Created from mqu on 2023-08-25 02:09:28.