Respiratory System Part 2 PDF

RESPIRATORY RESPIRATORY SYSTEM Marie A. Román Martínez, PhD Department of Biology Office hours: by appointment Email: [email protected] Copyright-This presentation is intended for educational purpose only. No part of this presentation may be reproduced or transmitted in any form without written pe...

RESPIRATORY RESPIRATORY SYSTEM Marie A. Román Martínez, PhD Department of Biology Office hours: by appointment Email: [email protected] Copyright-This presentation is intended for educational purpose only. No part of this presentation may be reproduced or transmitted in any form without written permission. Objectives 1. Describe the five processes involved in respiration. 2. List the functions of the respiratory system. 3. Describe the structures and functions of the respiratory system. 4. Describe the mechanism of breathing. 5. Describe the various respiratory volumes and capacities and the significance of each. 6. Describe the mechanisms of gas exchange in the lungs and the body tissues. 7. Describe how oxygen and carbon dioxide are transported by the blood. 8. Describe the major disorders of the respiratory system. 2 Expiration Process of moving air out of the lungs: Intra-alveolar pressure must be elevated above atmospheric pressure. Process of resting expiration: It is a passive process. Diaphragm and external intercostals relax. Thoracic cavity and lung return to original size. Aided by abundant elastic tissue in lungs and thoracic wall. 3 Expiration Process of resting expiration: (cont.) ↓lung volume, ↑intra-alveolar pressure to +1 cm H2O. High intra-alveolar pressure pushes air out of lungs. Air outflow continues until both pressures are equal. 4 Expiration Forceful expiration requires muscle contraction: Contraction of internal intercostal muscles. Depress and retract the ribs. Contraction of abdominal muscles. Force abdominal viscera and diaphragm upward. Muscle contraction further decreases volume of the thoracic cavity and lungs. Causes a greater increase in intraalveolar pressure, causing more air to flow out. 5 Respiratory Volumes and Capacities Healthy adult: 12 to 15 breathing cycles/min. Breathing cycle: one inspiration followed by one expiration. Volume of air inhaled and exhaled during resting or forceful breathing cycle varies. Size, age, sex, physical condition. Volumes 80% or less than healthy range indicate pulmonary disease. Spirometers are used to determine respiratory volumes. Produces a spirogram, a graphic record of air volume being exchanged. 6 Respiratory Volumes and Capacities Tidal volume (VT): Volume of air exchanged (inhaled or exhaled) during a resting breathing cycle. Approx. 500 ml. Inspiratory reserve volume (IRV): Maximum volume of air that can be forcefully inhaled after a tidal inspiration. Approx. 3,000 ml. 7 Respiratory Volumes and Capacities Expiratory reserve volume (ERV): Maximum volume of air forcefully exhaled after a tidal expiration. Approx. 1,100 ml. Residual volume (RV): Volume of air in lungs after expelling ERV. Approx. 1,200 ml. Exists because of intrapleural pressure and surfactant. 8 Respiratory Volumes and Capacities Respiratory capacities can be calculated by summation of two or more respiratory volumes. Vital capacity (VC): Maximum amount of air that can be forcefully exchanged. VT + IRV + ERV Approx. 4,600 ml Total lung capacity (TLC): VC + RV Approx. 5,800 ml 9 Control of Breathing Centers for involuntary control of breathing are located in the brainstem, where the medulla oblongata and the pons regulate breathing. Voluntary override of breathing is controlled by primary motor area of cerebral cortex. 10 Respiratory Rhythmicity Center Two bilateral groups of neurons compose the respiratory rhythmicity center in the medulla oblongata: Ventral respiratory group (VRG) Dorsal respiratory group (DRG) 11 Respiratory Rhythmicity Center Ventral respiratory group (VRG) Responsible for normal rhythmic cycle of breathing. Neurons rhythmically send action potentials to diaphragm and external intercostals. Action potentials cause muscles to contract; inspiration occurs for approx. 2 seconds. When action potentials stop, muscles relax; expiration occurs for approx. 3 seconds. This pattern of alternating neural activity and inactivity of the VRG produces the cyclic nature of inspiration and expiration. 12 Respiratory Rhythmicity Center Dorsal respiratory group (DRG) Center for receiving and integrating input from sensory sources. Sends action potentials to VRG to alter breathing as the needs of the body change (in accordance with the sensory input). Deeper or shallower, faster or slower. 13 Pontine Respiratory Group (PRG) Located in pons. Receives input from higher brain centers. Sends action potentials to DRG and VRG to modify breathing pattern. Has neurons that stimulate or inhibit the VRG and DRG. Can either speed up or slow down transition from inspiration to expiration. Alters the rate and depth of breathing. Adapts breathing to speaking, singing, exercise, sleep, and emotional responses (crying, gasping). 14 BREAK! 15 Chemicals Most important chemical factors in blood and cerebrospinal fluid (CSF) affecting respiration are: CO2 H+ By-product of CO2 transport. Increase CO2 concentration will increase H+ concentration. O2 The central chemoreceptors (sensory receptors that are sensitive to these factors) in medulla oblongata detect changes in H+ and CO2 in CSF. Are sensitive to increase in H+ and CO2. The peripheral chemoreceptors in carotid and aortic bodies detect changes in H+, CO2, and O2 in blood. Strategically located, especially to monitor blood going to the brain 16 If CO2 and H+ increase in the blood or CSF, DRG stimulates the VRG to increase rate and depth of breathing. Causes loss of CO2 and H+, which lowers levels to homeostasis. Chemicals If CO2 and H+ decrease in blood or CSF, breathing will be shallow and slow. Provides time for concentrations to increase back to homeostasis. Peripheral chemoreceptors in the carotid and aortic bodies are sensitive to a decline in blood O2 concentration. O2 levels have little effect on rate and depth of breathing unless they are very low. A drop of O2 seems to increase the sensitivity of peripheral chemoreceptors to changes in CO2 concentrations. 17 Inflation Reflex Baroreceptors are found in the bronchi, bronchioles, and visceral pleurae. Sensitive to lung inflation. Inspiration activates baroreceptors. Baroreceptors send action potentials via vagus nerve to the DRG. Action potentials causing inspiration are inhibited. Promotes expiration and prevents excessively deep inspirations that may damage the lungs. 18 Irritant Reflexes Irritant receptors are sensitive to chemical and physical irritants in respiratory tract. Such as smoke, dust, and excessive amounts of mucus. When stimulated by irritants, these receptors send action potentials to the DRG. DRG alter VRG function which triggers a reflex contraction of the respiratory muscles to trigger a sneeze or cough to expel the irritants from the respiratory tract. 19 Higher Brain Centers Action potentials voluntarily generated by cerebral cortex: Created when a person chooses to alter the pattern of resting breathing. Voluntary control is limited. Involuntary action potentials from cerebral cortex and hypothalamus. Created during emotional experiences that activate the autonomic division. Fear, anxiety, and excitement can lead to an increase in breathing rate. Sudden emotional experience, sharp pain, or sudden cold stimulus can cause apnea (momentarily stop breathing). 20 Body Temperature Increase temperature, increase breathing rate. Strenuous exercise or a fever. Decrease temperature, decrease breathing rate. 21 Alveolar Gas Exchange Gas exchange between air in pulmonary alveoli and blood in capillaries that surround them. Diffusion (O2 and CO2) across the respiratory membrane. Process of alveolar gas exchange: Alveolar air has higher concentration of O2 and lower concentration of CO2 than blood in capillaries. Type I Type II O2 moves from air into blood. CO2 moves from blood into air. Blood entering alveolar capillaries is O2 poor and CO2 rich. Blood leaving alveolar capillaries is O2 rich and CO2 poor. 22 Systemic Gas Exchange After blood has been oxygenated, it returns to the heart and is pumped throughout the body to supply the tissue cells through systemic gas exchange. Gas exchange between blood in capillaries and tissue cells. Involves diffusion across capillary walls. Process of systemic gas exchange: Blood entering tissues is O2 rich and CO2 poor. Tissue cells have a lower concentration of O2 and higher concentration of CO2 than blood in capillaries. O2 moves from blood into interstitial fluid and then into tissue cells. CO2 moves from tissue cells into interstitial fluid and then into blood. Blood leaving tissues is O2 poor and CO2 rich. 23 Transport of Respiratory Gases Oxygen transport: In alveolar capillaries, 98.5% of O2 enter RBCs and binds to heme of hemoglobin to form oxyhemoglobin (HbO2). 1.5% is dissolved in plasma. In resting body tissues, 25% of O2 is released so it can diffuse out of the capillary. Forms deoxyhemoglobin. 24 Transport of Respiratory Gases Oxygen Transport: The bond between O2 and hemoglobin is unstable. Reason why Hb is an effective carrier of oxygen. If surrounding O2 level is high, hemoglobin readily binds O2. If surround O2 level is low, hemoglobin readily releases O2. 25 Transport of Respiratory Gases Carbon Dioxide Transport: When CO2 diffuses into capillary blood, it is transported one of three ways. 7% is dissolved in plasma. 23% enters RBCs and combines with globin of hemoglobin to form carbaminohemoglobin (HbCO2). Hemoglobin can transport O2 and CO2 at the same time. CO2 and O2 have different binding sites on hemoglobin. 70% enter RBCs and combines with water to form carbonic acid (H2CO3). Reaction catalyzed by carbonic anhydrase. Carbonic acid rapidly breaks down (dissociates) into H+ and bicarbonate ions (HCO3-). 26 Transport of Respiratory Gases Carbon Dioxide Transport: Bicarbonate ions diffuse out of RBCs into plasma for transport to lungs. All of these reactions run in reverse in the lungs to release CO2 for diffusion into pulmonary alveoli. 27 Respiration (3D) https://anatomy.mheducation.com/html/apr.html?animal=human& 28 Disorders of the Respiratory System Respiratory disorders are grouped into: Inflammatory disorders Noninflamatory disorders 29 Inflammatory Disorders Chronic obstructive pulmonary disease (COPD) Group of disorders in which there is a long-term obstruction that reduces airflow to and from the lungs. Chronic bronchitis Emphysema Bronchitis: Inflammation of bronchi accompanied by excessive mucus production partially obstructing airflow. Acute bronchitis: viral or bacterial infection. Chronic bronchitis: chronic asthmatics and smokers (due to persistent exposure to irritants in tobacco smoke). 30 Inflammatory Disorders Emphysema: Due to long-term exposure to airborne irritants (especially tobacco smoke). Effects: Large spaces form when pulmonary alveoli rupture. Air trapped in pulmonary alveoli due to excess mucus production in bronchioles. Reduces respiratory surface area and impairs gas exchange. Exhaling requires voluntary effort. Uncommon except long-term smokers or people with long-term exposure to secondhand smoke. No cure but can be prevented and progressive deterioration can be stopped by removing the irritant (usually tobacco smoke). 31 Inflammatory Disorders Asthma: COPD with intermittent reduction in airflow. Characterized by wheezing upon exhalation and dyspnea (labored breathing). Due to bronchoconstriction. Allergic reactions to airborne substances. Hypersensitivity to pathogens infecting the bronchial tree. 32 Inflammatory Disorders Pneumonia: Acute inflammation of pulmonary alveoli caused by viral or bacterial infection. Pulmonary alveoli become filled with fluid, pathogens and WBCs. Reduces gas exchange space, resulting in low blood oxygen level. Pleurisy: Inflammation of pleurae. Can have two results: Decrease pleural fluid production. Causes sharp pains during breathing. Increase pleural fluid production: Causes increase in pressure on lungs. Impairs lung expansion. 33 Noninflammatory Disorders Infant respiratory distress syndrome (IRDS): Disease of newborn infants, usually those prematurely born. Due to insufficient surfactant production in pulmonary alveoli. Causes alveolar collapse. Without surfactant, pulmonary alveoli collapse after every expiration. Requires a lot of energy to perform each inhalation. 34