BIO2870 Chapter 23 Slides and Lecture Notes
BIO2870 Chapter 23 Slides and Lecture Notes Bio 2870
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Ch-23 The Respiratory System Nov-19-2015 Bio-2870 Anatomy and Physiology Chapter 23 The Respiratory System 1 Ch-23 The Respiratory System Nov-19-2015 Anatomy of the Heart Figure 20–6a-b The Sectional Anatomy of the Heart 2 Ch-23 The Respiratory System Nov-19-2015 Components of the Respiratory System ▯ Five Functions of the Respiratory System 1) Provides extensive gas exchange surface area between air and circulating blood 2) Moves air to and from exchange surfaces of lungs 3) Protects respiratory surfaces from outside environment 4) Produces sounds 5) Participates in olfactory sense 3 Ch-23 The Respiratory System Nov-19-2015 Components of the Respiratory System ▯ Organization of the Respiratory System ▯ The respiratory system is divided into ▯ Upper respiratory system: above the larynx ▯ Lower respiratory system: below the larynx ▯ The Respiratory Tract ▯ Consists of a conducting portion ▯ From nasal cavity to terminal bronchioles ▯ Consists of a respiratory portion ▯ The respiratory bronchioles and alveoli ▯ Alveoli ▯ Are air-filled pockets within the lungs ▯ Where all gas exchange takes place 4 Ch-23 The Respiratory System Nov-19-2015 Components of the Respiratory System Figure 23–1 The Components of the Respiratory System. 5 Ch-23 The Respiratory System Nov-19-2015 Components of the Respiratory System The Respiratory Epithelium ▯ For gases to exchange efficiently ▯ Alveoli walls must be very thin (<1 µm) ▯ Surface area must be very great (about 35 times the surface area of the body) Figure 23–2a The Respiratory Epithelium of the Nasal Cavity and Conducting System: A Surface View. 6 Ch-23 The Respiratory System Nov-19-2015 Components of the Respiratory System ▯ The Respiratory Mucosa ▯ Consists of ▯ An epithelial layer ▯ An areolar layer called the lamina propria ▯ Lines the conducting portion of respiratory system ▯ The Lamina Propria ▯ Underlying layer of areolar tissue that supports the respiratory epithelium ▯ In the upper respiratory system, trachea, and bronchi ▯ It contains mucous glands that secrete onto epithelial surface ▯ In the conducting portion of lower respiratory system ▯ It contains smooth muscle cells that encircle lumen of bronchioles 7 Ch-23 The Respiratory System Nov-19-2015 Components of the Respiratory System ▯ Structure of Respiratory Epithelium ▯ Changes along respiratory tract ▯ Pseudostratified columnar epithelium (superior portions of pharynx) ▯ Stratified squamous epithelium (inferior portions of pharynx) ▯ Pseudostratified columnar epithelium (lower respiratory system) ▯ Cuboidal epithelium with scattered cilia (smaller bronchioles) ▯ Simple squamous epithelium (alveoli) ▯ Alveolar Epithelium ▯ Is a very delicate, simple squamous epithelium ▯ Contains scattered and specialized cells ▯ Lines exchange surfaces of alveoli 8 Ch-23 The Respiratory System Nov-19-2015 Components of the Respiratory System Figure 23–2b, c The Respiratory Epithelium of the Nasal Cavity and Conducting System. 9 Ch-23 The Respiratory System Nov-19-2015 Components of the Respiratory System ▯ The Respiratory Defense System ▯ Consists of a series of filtration mechanisms ▯ Removes particles and pathogens ▯ Components of the Respiratory Defense System ▯ Mucous cells and mucous glands ▯ Produce mucus that bathes exposed surfaces (10μm or above particles stopped) ▯ Cilia ▯ Sweep debris trapped in mucus toward the pharynx (mucus escalator) (5-10 μm particles stopped) ▯ Filtration in nasal cavity removes large particles ▯ Alveolar macrophages engulf small particles that reach lungs (1-5μm particles stopped) 10 Ch-23 The Respiratory System Nov-19-2015 Upper Respiratory Tract Learn details covered in lecture and slides Figure 23–3c Structures of the Upper Respiratory System. 11 Ch-23 The Respiratory System Nov-19-2015 Upper Respiratory Tract ▯ The Pharynx ▯ A chamber shared by digestive and respiratory systems ▯ Extends from internal nares to entrances to larynx and esophagus ▯ Divided into : 1) The Nasopharynx (superior portion of pharynx) ▯ Contains pharyngeal tonsils and openings to left and right auditory tubes 2) The Oropharynx (middle portion of pharynx) ▯ Communicates with oral cavity 3) The Laryngopharynx (inferior portion of pharynx) ▯ Extends from hyoid bone to entrance of larynx and esophagus 12 Ch-23 The Respiratory System Nov-19-2015 The Lungs ▯ The Pleural Cavities and Pleural Membranes ▯ Two pleural cavities ▯ Are separated by the mediastinum ▯ Each pleural cavity ▯ Holds a lung ▯ Is lined with a serous membrane (the pleura) ▯ The Pleura ▯ Consists of two layers ▯ Parietal pleura ▯ Visceral pleura ▯ Pleural fluid ▯ Lubricates space between two layers 13 Ch-23 The Respiratory System Nov-19-2015 The Lungs ▯ The Bronchial Tree ▯ Is formed by the primary bronchi and their branches A. Extrapulmonary Bronchi ▯ The left and right bronchi branches outside the lungs B. Intrapulmonary Bronchi ▯ Branches within the lungs ▯ Primary Bronchus ▯ Branches to form secondary bronchi (lobar bronchi) ▯ One secondary bronchus goes to each lobe ▯ Secondary Bronchi ▯ Branch to form tertiary bronchi, also called the segmental bronchi ▯ Each segmental bronchus ▯ Supplies air to a single bronchopulmonary segment 14 Ch-23 The Respiratory System Nov-19-2015 The Lungs Figure 23–9 The Bronchi and Lobules of the Lung. 15 Ch-23 The Respiratory System Nov-19-2015 The Lungs ▯ Bronchopulmonary Segments ▯ The right lung has 10 ▯ The left lung has 8 or 9 ▯ Bronchial Structure ▯ The walls of primary, secondary, and tertiary bronchi ▯ Contain progressively less cartilage and more smooth muscle ▯ Increased smooth muscle tension affects airway constriction and resistance ▯ The Bronchioles ▯ Each tertiary bronchus branches into multiple bronchioles ▯ Bronchioles branch into terminal bronchioles ▯ One tertiary bronchus forms about 6500 terminal bronchioles ▯ Bronchiole Structure ▯ Bronchioles ▯ Have no cartilage ▯ Are dominated by smooth muscle 16 Ch-23 The Respiratory System Nov-19-2015 The Lungs ▯ Autonomic Control ▯ Regulates smooth muscle ▯ Controls diameter of bronchioles ▯ Controls airflow and resistance in lungs ▯ Bronchodilation ▯ Bronchoconstriction ▯ Dilation of bronchial airways ▯ Constricts bronchi ▯ Caused by sympathetic ANS ▯ Caused by: activation • parasympathetic ANS ▯ Reduces resistance activation • histamine release (allergic reactions) ▯ Bronchitis ▯ Asthma ▯ Inflammation of bronchial walls ▯ Excessive stimulation and ▯ Causes constriction and bronchoconstriction breathing difficulty ▯ Stimulation severely restricts airflow 17 Ch-23 The Respiratory System Nov-19-2015 The Lungs ▯ Surfaces of the Lungs ▯ Each terminal bronchiole delivers air to a single pulmonary lobule ▯ Each pulmonary lobule is supplied by pulmonary arteries and veins ▯ Exchange surfaces within the lobule ▯ Each terminal bronchiole branches to form several respiratory bronchioles, deliver air to gas exchange surfaces of lungs (alveoli) ▯ An Alveolus ▯ Respiratory bronchioles are connected to alveoli along alveolar ducts ▯ Alveolar ducts end at alveolar sacs ▯ Common chambers connected to many individual alveoli ▯ Has an extensive network of capillaries ▯ Is surrounded by elastic fibers 18 Ch-23 The Respiratory System Nov-19-2015 The Lungs ▯ Alveolar Epithelium ▯ Consists of simple squamous epithelium ▯ Consists of thin, delicate pneumocytes type I (site of gas diffusion) ▯ Patrolled by alveolar macrophages, also called dust cells ▯ Contains pneumocytes type II (septal cells) that produce surfactant Figure 23–10a Alveolar Organization: Basic Structure of a Portion of Single Lobule. 19 Ch-23 The Respiratory System Nov-19-2015 The Lungs ▯ Respiratory Membrane ▯ The thin membrane of alveoli where gas exchange takes place Three Layers of the Respiratory Membrane 1) Squamous epithelial lining of alveolus 2) Endothelial cells lining an adjacent capillary 3) Fused basal laminae between alveolar and endothelial cells Figure 23–10 d Alveolar Organization: The Respiratory Membrane. 20 Ch-23 The Respiratory System Nov-19-2015 The Lungs ▯ Surfactant ▯ Diffusion ▯ Is an oily secretion ▯ Across respiratory ▯ Contains phospholipids and membrane is very rapid proteins ▯ Because distance is short ▯ Coats alveolar surfaces and ▯ Gases (O2and CO )2are lipid reduces surface tension soluble ▯ Inflammation of Lobules ▯ Respiratory Distress ▯ Difficult respiration ▯ Also called pneumonia ▯ Due to alveolar collapse ▯ Causes fluid to leak into ▯ Caused when pneumocytes alveoli ▯ Compromises function of type II do not produce enough surfactant respiratory membrane 21 Ch-23 The Respiratory System Nov-19-2015 Introduction to Gas Exchange ▯ Respiration refers to two integrated processes ▯ External respiration ▯ Includes all processes involved in exchanging O2 and CO w2th the environment ▯ Internal respiration ▯ Also called cellular respiration ▯ Involves the uptake of O2and production of CO 2 within individual cells ▯ Pressure and Airflow to the Lungs ▯ Air flows from area of higher pressure to area of lower pressure ▯ A Respiratory Cycle ▯ Consists of ▯ An inspiration (inhalation) ▯ An expiration (exhalation) 22 Ch-23 The Respiratory System Nov-19-2015 Introduction to Gas Exchange Figure 23–11 An Overview of the Key Steps in Respiration . 23 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation ▯ Three Processes of External Respiration 1. Pulmonary ventilation (breathing) 2. Gas diffusion: ▯ Across membranes and capillaries 3. Transport of O 2nd CO : 2 ▯ Between alveolar capillaries ▯ Between capillary beds in other tissues 1) Pulmonary Ventilation ▯ Is the physical movement of air in and out of respiratory tract ▯ Provides alveolar ventilation ▯ Atmospheric Pressure ▯ The weight of air ▯ Has several important physiological effects 24 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation 1) Pulmonary Ventilation ▯ Causes volume changes that create changes in pressure ▯ Volume of thoracic cavity changes ▯ With expansion or contraction of diaphragm or rib cage Figure 23–14 Mechanisms of Pulmonary Ventilation. 25 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation ▯ Compliance ▯ An indicator of expandability ▯ Low compliance requires greater force ▯ High compliance requires less force ▯ Factors That Affect Compliance ▯ Connective tissue structure of the lungs ▯ Level of surfactant production ▯ Mobility of the thoracic cage ▯ Pressure Changes during Inhalation and Exhalation ▯ Can be measured inside or outside the lungs ▯ Normal atmospheric pressure: ▯ 1 atm or Patm at sea level: 760 mm Hg 26 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation ▯ The Intrapulmonary Pressure ▯ Also called intra-alveolar pressure ▯ Is relative to Patm ▯ In relaxed breathing, the difference between Patm and intrapulmonary pressure is small ▯ About -1 mm Hg on inhalation or +1 mm Hg on exhalation ▯ Maximum Intrapulmonary Pressure ▯ Maximum straining, a dangerous activity, can increase range ▯ From -30 mm Hg to +100 mm Hg ▯ The Intrapleural Pressure ▯ Pressure in space between parietal and visceral pleura ▯ Averages -4 mm Hg ▯ Maximum of -18 mm Hg ▯ Remains below Patm throughout respiratory cycle ▯ Tidal Volume ▯ Amount of air moved in and out of lungs in a single respiratory cycle 27 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation Figure 23–15 Pressure and Volume Changes during Inhalation and Exhalation. 28 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation ▯ The Respiratory Muscles ▯ Most important are ▯ The diaphragm ▯ External intercostal muscles of the ribs ▯ Accessory respiratory muscles: ▯ activated when respiration increases significantly ▯ The Mechanics of Breathing ▯ Inhalation : Always active ▯ Exhalation : Active or passive 29 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation ▯ The Mechanics of Breathing 1. Diaphragm: ▯ Contraction draws air into lungs ▯ 75% of normal air movement 2. External intercostal muscles: ▯ Assist inhalation ▯ 25% of normal air movement 3. Accessory muscles assist in elevating ribs: ▯ Sternocleidomastoid ▯ Serratus anterior specific names not required ▯ Pectoralis minor ▯ Scalene muscles 30 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation ▯ Muscles of Active Exhalation ▯ Internal intercostal and transversus thoracis muscles ▯ Depress the ribs ▯ Abdominal muscles ▯ Compress the abdomen ▯ Force diaphragm upward 31 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation Figure 23–15 The Respiratory Muscles. 32 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation Figure 23–15 The Respiratory Movements 33 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation ▯ Modes of Breathing ▯ Respiratory movements are classified ▯ By pattern of muscle activity ▯ Into quiet breathing and forced breathing 34 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation ▯ Quiet Breathing (Eupnea) ▯ Involves active inhalation and passive exhalation ▯ Diaphragmatic breathing or deep breathing ▯ Is dominated by diaphragm ▯ Costal breathing or shallow breathing ▯ Is dominated by ribcage movements ▯ Elastic Rebound ▯ When inhalation muscles relax ▯ Elastic components of muscles and lungs recoil ▯ Returning lungs and alveoli to original position ▯ Forced Breathing ▯ Also called hyperpnea ▯ Involves active inhalation and exhalation ▯ Assisted by accessory muscles ▯ Maximum levels occur in exhaustion 35 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation ▯ Respiratory Rates and Volumes ▯ Respiratory system adapts to changing oxygen demands by varying ▯ The number of breaths per minute (respiratory rate= 12) ▯ The volume of air moved per breath (tidal volume= 500ml) ▯ The Respiratory Minute Volume ▯ Amount of air moved per minute ▯ Is calculated by: respiratory rate ▯ tidal volume ▯ Measures pulmonary ventilation ▯ Anatomic Dead Space (= 150ml) ▯ Only a part of respiratory minute volume reaches alveolar exchange surfaces ▯ Volume of air remaining in conducting passages is anatomic dead space 36 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation ▯ Alveolar Ventilation ▯ Amount of air reaching alveoli each minute ▯ Calculated as: (tidal volume - anatomic dead space) ▯ respiratory rate ▯ Alveolar Gas Content ▯ Alveoli contain less O , more CO than atmospheric air 2 2 ▯ Because air mixes with exhaled air ▯ Alveolar Ventilation Rate ▯ Determined by respiratory rate and tidal volume ▯ For a given respiratory rate: ▯ increasing tidal volume increases alveolar ventilation rate ▯ For a given tidal volume: ▯ increasing respiratory rate increases alveolar ventilation ▯ Lung Volume (Spirometry) ▯ Total lung volume is divided into a series of volumes and capacities useful in diagnosing problems 37 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation ▯ Four Pulmonary Volumes 1) Resting tidal volume ▯ In a normal respiratory cycle 2) Expiratory reserve volume (ERV) ▯ After a normal exhalation 3) Residual volume ▯ After maximal exhalation ▯ Minimal volume (in a collapsed lung) 4) Inspiratory reserve volume (IRV) ▯ After a normal inspiration 38 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation ▯ Four Calculated Respiratory Capacities 1) Inspiratory capacity ▯ Tidal volume + inspiratory reserve volume 2) Functional residual capacity (FRC) ▯ Expiratory reserve volume + residual volume 3) Vital capacity ▯ Expiratory reserve volume + tidal volume + inspiratory reserve volume 4) Total lung capacity ▯ Vital capacity + residual volume 39 Ch-23 The Respiratory System Nov-19-2015 Pulmonary Ventilation ▯ Pulmonary Function Tests ▯ Measure rates and volumes of air movements Figure 23–17 Pulmonary Volumes and Capacities. 40 Ch-23 The Respiratory System Nov-19-2015 Gas Exchange ▯ Gas Exchange ▯ Occurs between blood and alveolar air ▯ Across the respiratory membrane ▯ Depends on ▯ Partial pressures of the gases ▯ Diffusion of molecules between gas and liquid ▯ Composition of Air ▯ Nitrogen (N ) is about 78.6% 2 ▯ Oxygen (O )2is about 20.9% ▯ Water vapor (H O) is about 0.5% 2 ▯ Carbon dioxide (CO ) 2s about 0.04% 41 Ch-23 The Respiratory System Nov-19-2015 Gas Exchange ▯ The Gas Laws (Boyle’s, Dalton’s, Henry’s) ▯ Diffusion occurs in response to concentration gradients ▯ Rate of diffusion depends on physical principles, or gas laws ▯ For example, Boyle’s law ▯ Dalton’s Law and Partial Pressures ▯ Atmospheric pressure (760 mm Hg) ▯ Produced by air molecules bumping into each other ▯ Each gas contributes to the total pressure ▯ In proportion to its number of molecules (Dalton’s law) ▯ Partial Pressure ▯ The pressure contributed by each gas in the atmosphere ▯ All partial pressures together add up to 760 mm Hg 42 Ch-23 The Respiratory System Nov-19-2015 Gas Exchange Diffusion Between Liquids and gases ▯ Henry’s Law ▯ When gas under pressure comes in contact with liquid ▯ Gas dissolves in liquid until equilibrium is reached ▯ At a given temperature ▯ Amount of a gas in solution is proportional to partial pressure of that gas Figure 23–18 Henry’s Law and the Relationship between Solubility and Pressure. 43 Ch-23 The Respiratory System Nov-19-2015 Gas Exchange ▯ Gas Content ▯ The actual amount of a gas in solution (at given partial pressure and temperature) depends on the solubility of that gas in that particular liquid ▯ Solubility in Body Fluids ▯ Normal Partial Pressures ▯ CO 2s very soluble ▯ In pulmonary vein plasma ▯ P = 40 mm Hg ▯ O2is less soluble CO2 ▯ N2has very low solubility ▯ PO = 100 mm Hg 2 ▯ PN2= 573 mm Hg 44 Ch-23 The Respiratory System Nov-19-2015 Gas Exchange ▯ Diffusion and the Respiratory Membrane ▯ Direction and rate of diffusion of gases across the respiratory membrane is determined by different partial pressures and solubility of gases. ▯ Efficiency of Gas Exchange Due to ▯ Substantial differences in partial pressure across the respiratory membrane ▯ Distances involved in gas exchange are short ▯ O 2nd CO ar2 lipid soluble ▯ Total surface area is large ▯ Blood flow and airflow are coordinated 45 Ch-23 The Respiratory System Nov-19-2015 Gas Exchange ▯ O and CO 2 2 ▯ Blood arriving in pulmonary arteries has ▯ Low P O2 ▯ High P CO2 ▯ The concentration gradient causes ▯ O 2o enter blood ▯ CO t2 leave blood ▯ Rapid exchange allows blood and alveolar air to reach equilibrium ▯ Mixing ▯ Oxygenated blood mixes with unoxygenated blood from conducting passageways ▯ Lowers the PO of blood entering systemic circuit (drops to about 2 95 mm Hg) 46 Ch-23 The Respiratory System Nov-19-2015 Gas Exchange ▯ Interstitial Fluid ▯ P 40 mm Hg O2 ▯ PCO 45 mm Hg 2 ▯ Concentration gradient in peripheral capillaries is opposite of lungs ▯ CO 2iffuses into blood ▯ O diffuses out of blood 2 ▯ Gas Pickup and Delivery ▯ Blood plasma cannot transport enough O or2CO to 2eet physiological needs 47 Ch-23 The Respiratory System Nov-19-2015 Gas Exchange Fig 23–19 Respiratory Processes and Partial Pressures in Respiration. 48 Ch-23 The Respiratory System Nov-19-2015 Gas Transport ▯ Red Blood Cells (RBCs) ▯ Transport O to, and CO from, peripheral tissues 2 2 ▯ Remove O a2d CO fro2 plasma, allowing gases to diffuse into blood ▯ Oxygen Transport ▯ O2binds to iron ions in hemoglobin (Hb) molecules ▯ In a reversible reaction ▯ Each RBC has about 280 million Hb molecules ▯ Each binds four oxygen molecules ▯ Environmental Factors Affecting Hemoglobin ▯ PO of blood 2 ▯ Blood pH ▯ Temperature ▯ Metabolic activity within RBCs 49 Ch-23 The Respiratory System Nov-19-2015 Gas Transport ▯ Oxygen Reserves ▯ O 2iffuses ▯ From peripheral capillaries (high P ) O2 ▯ Into interstitial fluid (loO P ) ▯ Amount of O released depends on interstitial P 2 O2 ▯ Up to 3/4 may be reserved by RBCs ▯ Carbon Monoxide ▯ CO from burning fuels ▯ Binds strongly to hemoglobin ▯ Takes the place of O 2 ▯ Can result in carbon monoxide poisoning ▯ Hemoglobin Saturation ▯ The percentage of heme units in a hemoglobin molecule ▯ That contain bound oxygen 50 Ch-23 The Respiratory System Nov-19-2015 Gas Transport ▯ Oxygen–Hemoglobin Saturation Curve ▯ Is a graph relating the saturation of hemoglobin to partial pressure of oxygen ▯ Higher P results in greater Hb saturation O2 ▯ Is a curve rather than a straight line ▯ Because Hb changes shape each time a molecule of O is bound 2 ▯ Each O 2ound makes next O bindi2g easier ▯ Allows Hb to bind O w2en O leve2s are low ▯ Is standardized for normal blood (pH 7.4, 37°C) ▯ When pH drops or temperature rises ▯ More oxygen is released ▯ Curve shifts to right ▯ When pH rises or temperature drops ▯ Less oxygen is released ▯ Curve shifts to left 51 Ch-23 The Respiratory System Nov-19-2015 Gas Transport Figure 23–20 An Oxygen—Hemoglobin Saturation Curve. 52 Ch-23 The Respiratory System Nov-19-2015 Gas Transport Figure 23–21 The Effects of pH and Temperature on Hemoglobin Saturation. ▯Oxygen–Hemoglobin Saturation Curve ▯ When pH drops or temperature rises ▯ More oxygen is released ▯ When pH rises or temperature drops ▯ Curve shifts to right ▯ Less oxygen is released ▯ Curve shifts to left 53 Ch-23 The Respiratory System Nov-19-2015 Gas Transport Fetal and Adult Hb ▯ The structure of fetal Hb ▯ Differs from that of adult Hb ▯ At the same P O 2 ▯ Fetal Hb binds more O 2 than adult Hb ▯ Which allows fetus to take O from maternal 2 blood Figure 23–22 A Functional Comparison of Fetal and Adult Hemoglobin. 54 Ch-23 The Respiratory System Nov-19-2015 Gas Transport ▯ Carbon Dioxide Transport (CO ) 2 ▯ Is generated as a by-product of aerobic metabolism (cellular respiration) ▯ CO 2n the bloodstream ▯ May be: ▯ converted to carbonic acid ▯ bound to protein portion of hemoglobin ▯ dissolved in plasma ▯ Bicarbonate Ions ▯ Move into plasma by an exchange mechanism (the - chloride shift) that takes in Cl ions without using ATP - ▯ the chloride shift: mass movement of Cl ions into RBCs (in systemic capillaries) 55 Ch-23 The Respiratory System Nov-19-2015 Gas Transport ▯ The Bohr Effect ▯ Is the effect of pH on hemoglobin-saturation curve ▯ Caused by CO 2 ▯ CO 2iffuses into RBC ▯ An enzyme, called carbonic anhydrase, catalyzes reaction with H O 2 ▯ Produces carbonic acid (H C2 ) 3 ▯ Carbonic acid (H C2 ) 3 + ▯ Dissociates into hydrogen ion (H ) and bicarbonate ion (HCO ) 3- ▯ Hydrogen ions diffuse out of RBC, lowering pH of plasma 56 Ch-23 The Respiratory System Nov-19-2015 Gas Transport CO i2 the Bloodstream ▯ 70% is transported as carbonic acid (H CO ) 2 3 ▯ Which dissociates into H+ and bicarbonate (HCO ) - 3 ▯ 23% is bound to amino groups of globular proteins in Hb molecule ▯ Forming carbaminohemoglobin ▯ 7% is transported as CO2 dissolved in plasma Figure 23–23 Carbon Dioxide Transport in Blood 57 Ch-23 The Respiratory System Nov-19-2015 Gas Transport Fig 23–24 A Summary of the Primary Gas Transport Mechanisms: Oxygen Transport. 58 Ch-23 The Respiratory System Nov-19-2015 Gas Transport Figure 23–24b A Summary of the Primary Gas Transport Mechanisms: Carbon Dioxide Transport. 59 Ch-23 The Respiratory System Nov-19-2015 Control of Respiration ▯ Peripheral and alveolar capillaries maintain balance during gas diffusion by ▯ Changes in blood flow and oxygen delivery ▯ Changes in depth and rate of respiration ▯ O delivery in tissues and pickup at lungs are regulated by: 2 1. Rising P CO levels: ▯ relaxes smooth muscle in arterioles and capillaries ▯ increases blood flow 2. Coordination of lung perfusion and alveolar ventilation: ▯ shifting blood flow 3. P CO levels: ▯ control bronchoconstriction and bronchodilation 60 Ch-23 The Respiratory System Nov-19-2015 Control of Respiration ▯ The Respiratory Centers of the Brain ▯ When oxygen demand rises ▯ Cardiac output and respiratory rates increase under neural control: ▯ have both voluntary and involuntary components ▯ Involuntary Centers ▯ Regulate respiratory muscles ▯ In response to sensory information ▯ Voluntary Centers ▯ In cerebral cortex affect ▯ Respiratory centers of pons and medulla oblongata ▯ Motor neurons that control respiratory muscles 61 Ch-23 The Respiratory System Nov-19-2015 Control of Respiration ▯ The Respiratory Centers ▯ Three pairs of nuclei in the reticular formation of medulla oblongata and pons Respiratory Rhythmicity Centers of the Medulla Oblongata ▯ Set the pace of respiration ▯ Can be divided into two groups ▯ Dorsal respiratory group (DRG) ▯ Inspiratory center ▯ Functions in quiet and forced breathing ▯ Ventral respiratory group (VRG) ▯ Inspiratory and expiratory center ▯ Functions only in forced breathing 62 Ch-23 The Respiratory System Nov-19-2015 Control of Respiration ▯ Quiet Breathing ▯ Brief activity in the DRG ▯ Stimulates inspiratory muscles ▯ DRG neurons become inactive ▯ Allowing passive exhalation ▯ Forced Breathing ▯ Increased activity in DRG ▯ Stimulates VRG ▯ Which activates accessory inspiratory muscles ▯ After inhalation ▯ Expiratory center neurons stimulate active exhalation 63 Ch-23 The Respiratory System Nov-19-2015 Control of Respiration Figure 23–25 Basic Regulatory Patterns of Respiration . 64 Ch-23 The Respiratory System Nov-19-2015 Control of Respiration ▯ The Apneustic and Pneumotaxic Centers of the Pons ▯ Paired nuclei that adjust output of respiratory rhythmicity centers ▯ Regulating respiratory rate and depth of respiration ▯ Apneustic Center ▯ Provides continuous stimulation to its DRG center ▯ Pneumotaxic Centers ▯ Inhibit the apneustic centers ▯ Promote passive or active exhalation ▯ Respiratory Centers and Reflex Controls ▯ Interactions between VRG and DRG ▯ Establish basic pace and depth of respiration ▯ The pneumotaxic center ▯ Modifies the pace 65 Ch-23 The Respiratory System Nov-19-2015 Control of Respiration Figure 23–26 Control of Respiration. 66 Ch-23 The Respiratory System Nov-19-2015 Figure 23–26 Control of Respiration. A & P Fall-2015 67 Ch-23 The Respiratory System Nov-19-2015 Control of Respiration ▯ SIDS ▯ Also known as sudden infant death syndrome ▯ Disrupts normal respiratory reflex pattern ▯ May result from connection problems between pacemaker complex and respiratory centers 68 Ch-23 The Respiratory System Nov-19-2015 Control of Respiration ▯ Five Sensory Modifiers of Respiratory Center Activities 1) Chemoreceptors are sensitive to P CO2, O 2 or pH of blood or cerebrospinal fluid 2) Baroreceptors in aortic or carotid sinuses are sensitive to changes in blood pressure 3) Stretch receptors respond to changes in lung volume 4) Irritating physical or chemical stimuli in nasal cavity, larynx, or bronchial tree 5) Other sensations including pain, changes in body temperature, abnormal visceral sensations 69 Ch-23 The Respiratory System Nov-19-2015 Control of Respiration ▯ Hypercapnia ▯ An increase in arterial CO ▯ Stimulates chemoreceptors in the medulla oblongata ▯ To restore homeostasis ▯ Hypercapnia and Hypocapnia ▯ Hypoventilation is a common cause of hypercapnia ▯ Abnormally low respiration rate: ▯ Allows CO buildup in blood 2 ▯ Excessive ventilation, hyperventilation, results in abnormally low PCO (hypocapnia) 2 ▯ Stimulates chemoreceptors to decrease respiratory rate 70 Ch-23 The Respiratory System Nov-19-2015 Control of Respiration Figure 23–27 The Chemoreceptor Response to Changes in PCO 2 71 Ch-23 The Respiratory System Nov-19-2015 Control of Respiration ▯ Protective Reflexes ▯ Triggered by receptors in epithelium of respiratory tract when lungs are exposed to ▯ Toxic vapors ▯ Chemical irritants ▯ Mechanical stimulation ▯ Cause sneezing, coughing, and laryngeal spasm ▯ Apnea ▯ A period of suspended respiration ▯ Normally followed by explosive exhalation to clear airways ▯ Sneezing and coughing ▯ Laryngeal Spasm ▯ Temporarily closes airway ▯ To prevent foreign substances from entering 72 Ch-23 The Respiratory System Nov-19-2015 Control of Respiration Voluntary Control of Respiration 1. Strong emotions: ▯ can stimulate respiratory centers in hypothalamus 2. Emotional stress: ▯ can activate sympathetic or parasympathetic division of ANS ▯ causing bronchodilation or bronchoconstriction 3. Anticipation of strenuous exercise: ▯ can increase respiratory rate and cardiac output ▯ by sympathetic stimulation 73 Ch-23 The Respiratory System Nov-19-2015 Control of Respiration Changes in the Respiratory System at Birth 1. Before birth: ▯ pulmonary vessels are collapsed 4. Large drop in pressure ▯ lungs contain no air at first breath: 2. During delivery: ▯ pulls blood into pulmonary circulation ▯ placental connection is lost ▯ closing foramen ovale and ▯ blood P O2falls ductus arteriosus ▯ PCO2 rises ▯ redirecting fetal blood 3. At birth: circulation patterns ▯ newborn overcomes force of surface tension to inflate 5. Subsequent breaths: ▯ fully inflate alveoli bronchial tree and alveoli and take first breath 74 Ch-23 The Respiratory System Nov-19-2015 Integration with Other Systems ▯ Maintaining homeostatic O and CO levels in 2 2 peripheral tissues requires coordination between several systems ▯ Particularly the respiratory and cardiovascular systems ▯ Coordination of Respiratory and Cardiovascular Systems ▯ Improves efficiency of gas exchange by controlling lung perfusion ▯ Increases respiratory drive through chemoreceptor stimulation ▯ Raises cardiac output and blood flow through baroreceptor stimulation 75
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