KNES 323: Integrative Physiology - Respiratory 1 (PDF)

KNES 323: Integrative Physiology Respiratory 1 Wednesday October 16, 2024 KNES 323: Integrative Physiology Respiratory 1 Wednesday October 16, 2024 Class Outline 1. Introduction 2. Key Respiratory Structures 3. The Lungs 4. Blood Supply 5. Breathing...

KNES 323: Integrative Physiology Respiratory 1 Wednesday October 16, 2024 KNES 323: Integrative Physiology Respiratory 1 Wednesday October 16, 2024 Class Outline 1. Introduction 2. Key Respiratory Structures 3. The Lungs 4. Blood Supply 5. Breathing Mechanisms Introduction Introduction The goal of the respiratory system is fairly simple… We use it to bring oxygen into ⑳ our body and we exhale carbon dioxide from - our body ↳ more important Change [PAS) But which side of the system drives our desire to breathe? (CO2)  Introduction To address this question, let’s go back to earlier in the semester for a moment: Every cell in our body uses cellular respiration at some point to create ATP For oxidative phosphorylation to occur, oxygen is consumed, and carbon dioxide is released as a waste product from the reaction Introduction So, which side of the equation drives our desire to breathe? Although oxygen is a critical need for cells to function, it is actually the accumulation of carbon dioxide that we need to get rid of drives our need to breathe On 100mMercury (50-300 = 49-TSmL/oray (for its = drapes) CO2= Why? Introduction As we have mentioned, the body aims to maintain it arterial pH in the range of 7.35-7.45 pH is based on the concentration of H+ in the blood stream which is directly related to the carbon dioxide levels Under normal circumstances it is the CO2 levels in your blood which triggers breathing Introduction CO 2 exhaled O 2 inhaled Respiration is the exchange of Pulmonary$ventilation$ (breathing) gases between the atmosphere, Alveoli CO 2 O blood, and cells and occurs over 2 three processes: CO 2 Pulmonary2 capillaries O2 Ventilation (breathing) (a)$External$ (pulmonary)$ respiration External (pulmonary) alvoli > - respiration Internal (tissue) respiration cellular level = The cardiovascular system assists (b)$Internal$ the respiratory system during (tissue)respiration internal respiration by CO 2 Systemic2 O2 transporting gases to the tissues capillaries for gas exchange CO 2 O2 Introduction Therefore, the major organs of the respiratory system function primarily to: - Provide oxygen to body tissues for cellular respiration Remove carbon dioxide which is one of the main waste products of cellular respiration Aids in the maintenance of acid-base balances Key Respiratory Structures Key Respiratory Structures The respiratory system can be divided based on the functions of the areas into a conducting zone and a respiratory zoneCredi present) The conducting zone of the respiratory system includes the organs and structuresO not directly involved in gas exchange The respiratory zone is the location where gas exchange occurs Key Respiratory Structures Conducting Zone The conducting zone main functions are to: Provide a route for incoming and outgoing air Remove debris and pathogens from the incoming air Warm and humidify the incoming air Key Respiratory Structures Conducting Zone The major entrance and exit for the respiratory system is through the o - nose The nose is divided into two major sections: External nose Internal nose (nasal cavity) Key Respiratory Structures Conducting Zone The nares open into the nasal cavity, which is separated into left and right sections by the nasal septum Each lateral wall of the nasal cavity has three bony projections (nasal conchae) This portion of the conducting zone: Cleans and warms the air Traps water to prevent dehydration Filters air via hairs and mucous Detects odours  Key Respiratory Structures Conducting Zone The trachea (windpipe) extends from the larynx toward the lungs and is formed by 16 to 20 stacked, C-shaped pieces of hyaline cartilage connected with dense connective tissue and open posteriorly - The nature of this design allows the trachea to stretch and expand slightly during inhalation and exhalation It also provides structural support which prevents the trachea from collapsing (especially during inhalation) Key Respiratory Structures Conducting Zone The main function of the bronchi, like other conducting zone structures, is to provide a passageway for air to move into and out of each lung Additionally, the mucous membrane along this path - trap debris and pathogens from entering the respiratory zone  Key Respiratory Structures Conducting Zone As the airways branch further and further- bronchial tree (respiratory tree) is the collective term used for these multiple-branched airways Each branch of the tree is known as a generation, with the trachea starting as generation 0 - X The primary bronchi is the 1st generation Generations 2-10 consist of the lobar and segmental bronchi The bronchioles and terminal bronchioles make up generations 11-16 The conducting zone ends at the 16th generation  Key Respiratory Structures Respiratory Zone In contrast to the conducting zone, the respiratory zone includes structures directly involved in gas exchange The respiratory zone begins where the terminal bronchioles join the smallest type of bronchiole The respiratory bronchiole (generations 17-19) Leads to an alveolar duct (generations 20-22) Finally open into an alveolar sac (23rd generation)  Key Respiratory Structures Respiratory Zone The muscular walls of the bronchioles and smaller airways do not contain cartilage like those of the bronchi This muscular wall enables the bronchioles to alter diameter thus increasing or decreasing airflow through the tube Bronchoconstriction – parasympathetic activation and histamine release (allergies, asthma) Bronchodilation – sympathetic activation, catecholamine release Key Respiratory Structures Respiratory Zone An alveolar sac is a cluster of many Terminal bronchiole individual alveoli where gas exchange Pulmonary arteriole occurs with the external environment Pulmonary0venule Lymphatic vessel 6 Each alveolus is a tiny sac with elastic walls Respiratory.bronchiole which stretch during air intake, greatly Elastic0 connective Alveoli tissue increasing the surface area available for gas Alveolar.ducts exchange The alveoli are connected to their Pulmonary0 capillary neighbours by alveolar pores, which help & Alveolar.sac Visceral0pleura maintain equal air pressure throughout the Alveoli alveoli and lung - Key Respiratory Structures Monocyte Respiratory Zone Reticular$fiber The alveolar wall consists of two major Elastic$fiber cell types: Type I alveolar cells (highly Alveolar$sac 8 permeable to gases, G ~97% of all Type(II(alveolar (septal)$cell alveolar cells) Type II alveolar cells (secretes Respiratory( membrane pulmonary surfactant, acts as a Alveolus lubricant for the lungs and reduces Diffusion Red$blood$cell surface tension) O of$O2 Type(I(alveolar( Capillary(endothelium cell Alveolar macrophages roam around the Diffusion of$CO2 Capillary(basement( alveolar walls and function to remove O Alveolar membrane macrophage((dust)cell) debris and pathogens which have Alveolus Epithelial(basement membrane reached the alveoli Red$blood$cell$in$ Type(I(alveolar(cell pulmonary$ Interstitial$space capillary Alveolar$fluid$with$surfactant Key Respiratory Structures Respiratory Zone The simple squamous epithelium formed by type I alveolar cells is attached to a thin, elastic basement membrane which borders the endothelial membrane of capillaries The thin respiratory membrane allows gases to readily cross by simple diffusion allowing O2 to be picked up by the blood for transport and CO2 to be released into the air of the alveoli The Lungs The Lungs When we typically think about the respiratory system, the first organ we normally consider is the lung Each lung contains the structures of both the conducting - and respiratory zones The main function is to take in O2 from the atmosphere and release the CO2 produced in the body To accomplish this the lungs exchange respiratory gases across a very large surface area (~70-75 square meters) The Lungs Each lung is covered with a connective tissue membrane Another membrane lines the inside of the hollow chest or Thoracic - cavity There is a small space between the wall of the chest cavity and the - lungs themselves (Pleural cavity) It contains lubricating fluid - (pleural fluid) which keeps the membranes from sticking or rubbing together The Lungs The right lung is shorter and wider than the left lung, and the left lung occupies a smaller volume than the right This is due to the cardiac notch which is an indentation on the surface of the left lung, and it allows space for the heart In contrast to the heart, the apex of the lung is the superior region, whereas the6 base is the region near the diaphragm Blood Supply Blood Supply The blood supply of the lungs plays an important role in gas exchange and serves as a transport system for gases throughout the body Blood Supply The pulmonary artery (arising from the pulmonary trunk) carries deoxygenated, arterial blood to the alveoli The pulmonary artery branches multiple times as it follows the bronchi, and each branch becomes progressively smaller in diameter One arteriole and the accompanying venule supply and drain each pulmonary lobule * : 1 : 1 pulmonaryi unae Blood Supply As they near the alveoli, the pulmonary arteries become the pulmonary capillary network The capillaries branch and follow the bronchioles and structure of the alveoli It is at this point that the capillary wall meets the alveolar wall, creating the respiratory membrane Once the blood is oxygenated, it drains from the alveoli by way of multiple pulmonary venules and veins, which eventually exit the lungs through the hilum Breathing Mechanisms Breathing Mechanisms The alveolar and intrapleural pressures are dependent on certain physical features of the lung However, the ability to breathe (air enter the lungs during inspiration and exiting during expiration) is dependent on the air pressure of the atmosphere and the air pressure within the lungs Breathing Mechanisms At a constant temperature (body temperature is maintained by homeostasis), changing the volume occupied by the gas changes the pressure -Boyle’s law describes the relationship between volume and - pressure in a gas at a constant temperature Breathing Mechanisms Boyle discovered the pressure of a gas is inversely - - proportional to its volume: - If volume increases, pressure decreases if volume decreases, pressure increases Boyle’s law is expressed by the following formula: P 1 V1 = P 2 V2 Breathing Mechanisms Pulmonary ventilation is the act of breathing, which can be described as the movement of air into and out of the lungs - The major mechanisms driving pulmonary ventilation are: atmospheric pressure air pressure within the -alveoli, called alveolar pressure pressure within the pleural cavity, called intrapleural - pressure Breathing Mechanisms Atmospheric(pressure(=(760(mmhg Atmospheric(pressure(=(760(mmhg Atmospheric pressure is the amount of force that is exerted by gases in the air surrounding Alveolar( Alveolar(pressure(= - pressure(= 758(mmHg any given surface, such as the 760(mmHg body Intrapleural Intrapleural pressure(= pressure(= 754(mmHg 756(mmHg In physiology, we typically express it in millimeters of Atmospheric(pressure(=(760(mmHg mercury (mm Hg) with sea level pressure being equal toO 760 Alveolar(pressure(= mmHg (Sea Level) 762(mmHg Intrapleural pressure(= A negative pressure is Patm Breathing Mechanisms Intra-alveolar pressure is the pressure of the air within the alveoli, which changes during the different phases of breathing Because the alveoli are connected to the atmosphere via the tubing of the airways, the alveoli are able to ventilate the gases of the body with the external environment ⑭ environment external Breathing Mechanisms Intrapleural pressure is the pressure of the air within - the pleural cavity, between the visceral and parietal pleurae Similar to intra-alveolar pressure, intrapleural pressure also changes during the different phases of breathing Breathing Mechanisms Competing forces within the thorax cause the formation of the negative intrapleural pressure: Elasticity of the lungs pulls the lungs inward and - away from the thoracic wall Alveolar fluid surface tension of, which is mostly - water, also creates an inward pull of the lung tissue Breathing Mechanisms The inward tension from the lungs is countered by opposing forces from the pleural fluid and thoracic wall The natural elasticity of the chest wall (compliance) wants to expand outward and thus opposes the inward pull of the lungs This creates a Pleural cavity surface tension which pulls the lungs outward Breathing Mechanisms Ultimately, the outward pull (of the chest wall) is slightly greater than the inward pull (of the lungs) This results in creating a negative pressure between the pleural membranes This difference is known as the transmural pressure Breathing Mechanisms Thus, the intrpleural pressure is always lower than, or negative to, the intra-alveolar pressure (and therefore is also less than atmospheric pressure) Although it fluctuates slightly during inspiration and expiration, transmural pressure remains ~-3 to -6 mmHg throughout the breathing cycle Breathing Mechanisms The lungs themselves are passive during breathing and are not involved in creating the movement that helps inspiration and expiration Ventilation instead is dependent upon the contraction - and relaxation of muscle fibers of both the diaphragm and6thorax Breathing Mechanisms Other characteristics of the lungs also influence F A - -3 = the effort expended for > - & - & ventilation ~ - & Much like the blood - - = vessels, the size of the 2 Y 3 airway is the primary & - & & factor affecting ⑳resistance which will impact airflow KNES 323: Integrative Physiology Respiratory 2 Friday October 18, 2024 Class Outline Inhalation 1. Pulmonary Ventilation Inspiratory Inspiratory Vital Total reserve 2. Volumes and Capacities capacity capacity lung volume Exhalation 3600%ml 4800%ml capacity 3100%ml (2400%ml) (3100%ml) 6000%ml (1900%ml) (4200%ml) 3. Ventilation Control 4. Gas Exchange Tidal volume%500%ml Expiratory reserve volume End%of Start%of 1200%ml record record Functional (700%ml) residual capacity Residual 2400%ml volume (1800%ml) 1200%ml (1100%ml) Lung% volumes Lung% capacities%(combinations% of%lung% volumes) Pulmonary Ventilation Pulmonary Ventilation The difference in pressures drives pulmonary ventilation because air flows down a pressure gradient, that is, air flows from an area of higher pressure to an area of lower pressure - A respiratory cycle is one sequence of inspiration and expiration Pulmonary Ventilation Air flows into the lungs Atmospheric(pressure(=(760(mmhg Atmospheric(pressure(=(760(mmhg (inspiration) PaPia) Pip atmospheric pressure is greater than intra-alveolar pressure, Alveolar( Alveolar(pressure(= and intra-alveolar pressure is pressure(= 758(mmHg greater than intrapleural 760(mmHg pressure, air flows in Intrapleural Intrapleural pressure(= 754(mmHg pressure(= Air flows out of the lungs 756(mmHg (Expiration) PL> Pa during expiration based on the Atmospheric(pressure(=(760(mmHg same principle; pressure within the lungs becomes greater than the atmospheric pressure, air is Alveolar(pressure(= 762(mmHg expelled Intrapleural pressure(= 756(mmHg Pulmonary Ventilation In general, two muscle groups are used during normal inspiration: the diaphragm and the external intercostal muscles Additional muscles can be used if a bigger breath is required When the diaphragm contracts, it moves inferiorly toward the abdominal cavity, creating a larger thoracic cavity and more space for the lungs Contraction of the external intercostal muscles moves the ribs upward and outward, causing the rib cage to expand, which increases the volume of the thoracic cavity  Pulmonary Ventilation The process of normal expiration is passive - The elasticity of the lung tissue causes the lung to recoil, as the diaphragm and intercostal muscles relax As a result, the thoracic cavity and lungs decrease in volume, causing an increase in pressure in the thoracic cavity When the pressure rises above atmospheric pressure, the pressure gradient causes air to leave the lungs Pulmonary Ventilation There are different types, or modes, of breathing each of which require a slightly different process to allow inspiration and expiration Quiet breathing (eupnea) is a mode of - breathing that occurs at rest and does not require the cognitive thought of the individual During quiet breathing, the diaphragm and external intercostals both must contract Pulmonary Ventilation Diaphragmatic breathing (deep breathing) requires the diaphragm to contract As the diaphragm relaxes, air passively leaves the lungs Costal breathing (shallow breathing) requires contraction of the intercostal muscles As the intercostal muscles relax, air passively leaves the lungs Both of these forms of breathing typically require cognitive thought * Pulmonary Ventilation Additionally, forced breathing can occur during coughing, exercise or actions that require the active manipulation of - breathing, such as singing During forced breathing, inspiration and expiration both occur due to muscle contractions Forced Inspiration uses the diaphragm, intercostal muscles and other accessory muscles The accessory muscles lift the thoracic wall, increasing lung volume Pulmonary Ventilation Forced expiration contracts the accessory muscles of the abdomen which forces abdominal organs upward - against the diaphragm, pushing the diaphragm further into the thorax and forcing more air out The internal intercostals also help to compress the rib cage further reduces thoracic volume Volumes and Capacities Volumes and Capacities Respiratory volume is the term used for various volumes of air moved by or associated with the lungs at a given point in the respiratory cycle There are four major types of respiratory volumes: OTidal Inspiratory reserve Expiratory reserve Residual Volumes and Capacities Tidal volume (TV) Amount of air that normally enters the lungs during quiet Inhalation breathing (~500ml) Inspiratory reserve Inspiratory capacity Vital capacity Total lung volume Exhalation 3600%ml 4800%ml capacity 3100%ml (2400%ml) (3100%ml) 6000%ml (1900%ml) Inspiratory reserve volume (IRV) (4200%ml) Produced by a deep inhalation, beyond a normal Tidal volume%500%ml tidal inspiration and Expiratory represents the extra volume reserve volume End%of Start%of that can be brought into the 1200%ml (700%ml) record record Functional residual lungs during a forced Residual capacity 2400%ml inspiration volume 1200%ml (1800%ml) (1100%ml) Lung%volumes Lung%capacities%(combinations%of%lung%volumes) Volumes and Capacities Expiratory reserve volume (ERV) Amount of air you can Inhalation forcefully exhale past a Inspiratory reserve Inspiratory Vital Total normal tidal expiration capacity capacity lung volume Exhalation 3600%ml 4800%ml capacity 3100%ml (2400%ml) (3100%ml) 6000%ml (1900%ml) Residual volume (RV) (4200%ml) The air left in the lungs if you exhale as much air as Tidal volume%500%ml possible. Expiratory reserve The residual volume makes volume 1200%ml End%of record Start%of record breathing easier by Functional (700%ml) residual preventing the alveoli from capacity Residual 2400%ml collapsing volume (1800%ml) 1200%ml (1100%ml) Lung%volumes Lung%capacities%(combinations%of%lung%volumes) Volumes and Capacities Respiratory capacities are the combination of two or more selected Inhalation volumes, which further describes the amount of air in the lungs during a Inspiratory reserve Inspiratory Vital Total given time volume 3100%ml Exhalation capacity 3600%ml capacity 4800%ml lung capacity (2400%ml) (3100%ml) 6000%ml Total lung capacity (TLC) (1900%ml) (4200%ml) The sum of all of the lung volumes (TV, ERV, IRV, and RV), which Tidal represents the total amount of air volume%500%ml a person can hold in the lungs Expiratory after a forceful inhalation reserve volume End%of Start%of 1200%ml record record Functional TLC is about 6000 ml for men, and (700%ml) residual about 4200 ml for women Residual capacity 2400%ml volume (1800%ml) 1200%ml (1100%ml) Lung%volumes Lung%capacities%(combinations%of%lung%volumes) Volumes and Capacities Vital capacity (VC) The amount of air a person can move into or out of his or her Inhalation lungs, and is the sum of all of Inspiratory reserve Inspiratory Vital Total the volumes except residual capacity capacity lung volume Exhalation 3600%ml 4800%ml capacity 3100%ml volume (TV, ERV, and IRV) (2400%ml) (3100%ml) 6000%ml (1900%ml) (4200%ml) Typically, is between 3000 and 5000 ml Tidal volume%500%ml Inspiratory capacity (IC) Expiratory the maximum amount of air reserve volume End%of Start%of record record that can be inhaled past a 1200%ml Functional (700%ml) residual normal tidal expiration (TV and Residual capacity 2400%ml IRV) volume 1200%ml (1100%ml) (1800%ml) Lung%volumes Lung%capacities%(combinations%of%lung%volumes) Volumes and Capacities ↑ Functional residual capacity (FRC) Inhalation The amount of air that Inspiratory Inspiratory Vital remains in the lung Total reserve capacity capacity lung volume Exhalation 3600%ml 4800%ml capacity after a normal tidal 3100%ml (2400%ml) (3100%ml) 6000%ml (1900%ml) (4200%ml) expiration (ERV and RV) We are able to obtain Tidal volume%500%ml clinical information Expiratory reserve End%of Start%of regarding the values volume 1200%ml record record Functional (700%ml) involved in FVC with a residual capacity Residual 2400%ml flow-volume loop volume 1200%ml (1100%ml) (1800%ml) Lung%volumes Lung%capacities%(combinations%of%lung%volumes) Volumes and Capacities Volumes and Capacities In addition to the air that creates respiratory volumes, the respiratory system also contains anatomical dead space, which is air that is present in the airway that never reaches the alveoli and therefore never participates in gas exchange Volumes and Capacities Alveolar (physiological) dead space involves air found within alveoli that are unable to function, such as those affected by disease or abnormal blood flow Total dead space is the anatomical dead space and alveolar dead space together, and represents all of the air in the respiratory system that is not being used in the gas exchange process (~150 ml) Ventilation Control Ventilation Control Respiratory rate is the total number of breaths (respiratory cycles) occurring each minute It is controlled by the respiratory center located within the medulla oblongata in the brain, which responds primarily to changes in blood CO2, O2, and pH levels  Ventilation Control The medulla oblongata contains the dorsal respiratory group (DRG) and the ventral respiratory group (VRG) The DRG is involved in maintaining a constant breathing rhythm by stimulating the diaphragm and (Normal breathing) intercostal muscles to contract, z resulting in inspiration When activity in the DRG ceases, it no longer stimulates the diaphragm and intercostals to contract, allowing them to relax, resulting in expiration Ventilation Control The medulla oblongata contains the dorsal respiratory group (DRG) and the ventral respiratory group (VRG) The VRG is involved in forced breathing, as the neurons in the VRG stimulate the (forced breathing) accessory muscles involved in forced breathing to contract, resulting in forced inspiration The VRG also stimulates the accessory muscles to contract in forced expiration Ventilation Control The second respiratory center of the brain is located within the pons This breathing center helps stimulate and inhibit the neurons in the DRG Caffects DRGS This provides additional control for the depth of inspiration, particularly for deep breathing The inhibition of DRG neuron activity, allowing relaxation after inspiration and results in expiration Ventilation Control Dorsal'respiratory'group'(DRG) Active Inactive 2'seconds 3'seconds Diaphragm'contracts' Diaphragm'relaxes'and' and'external'intercostal external'intercostal muscles' muscles'contract'during' become'less'active'and' relax,'followed'by'elastic' their'most'active'phase recoil'of'lungs Normal'quiet'inhalation Normal'quiet'exhalation (a)'During'normal'quiet'breathing Ventilation Control Activates Dorsal)respiratory)group) Ventral)respiratory)group) Ventral)respiratory)group) (DRG) (VRG))(forceful) (VRG))(forceful)exhalation) inhalation)neurons) neurons) Diaphragm)contracts)and) Accessory)muscles)of) Accessory)muscles)of) external)intercostal inhalation) exhalation)(internal)intercostal,) muscles)contract)during) (sternocleidomastoid,) external)oblique,)internal) scalene,)and)pectoralis oblique,)transversus their)most)active)stage minor)muscles))contract abdominis,)and)rectus) abdominis muscles))contract Forceful)inhalation Forceful)exhalation (b))During)forceful)breathing Ventilation Control As we discussed, the major factor that stimulates the medulla oblongata and pons to produce respiration is typically not O2 concentration, but rather the blood CO2 concentration CO2 is a waste product of cellular respiration and can be toxic and are sensed by chemoreceptors Central chemoreceptors are located in the brain and brainstem Peripheral chemoreceptors is are located in the carotid bodies and aortic arch  Ventilation Control Changes in CO2 or H+ concentration stimulate the chemoreceptors, which in turn signal the respiration centers Blood CO2 concentration increases This causes bicarbonate buffer system to increase in H+ in the extracellular Leads to a decrease in pH and triggers the central and peripheral chemoreceptors In turn, they stimulate the respiratory centre to contract the diaphragm and external intercostals to increase the rate and depth of respiration Allows more CO2 to be expelled, decreasing H+ in the blood and raises pH Ventilation Control In contrast, low levels of CO2 in the blood cause low levels of H+ (increased pH) Leading to a decrease in firing rate of the central and peripheral chemoreceptors In turn causes a decrease in the stimulation of the respiratory centres leading to a decreased rate and depth of pulmonary ventilation, producing shallow, slow breathing This allows CO2 to build up in the blood and decreases pH  Ventilation Control Blood levels of O2 can also influencing respiratory rate by triggering the peripheral chemoreceptors when blood O2 levels become quite low ( O > H O > CO 2 2 2 2 The difference are: Alveolar air also has higher levels of CO2 and lower levels of O2 as a result of cellular respiration Alveolar air has more H2O (47 mmHg) than atmospheric air because the respiratory system humidifies the air as it is inhaled  (distance) (SA) (sombility) (come) Gas Exchange [ga) = Additional factors for consideration for gas exchange is the distance diffusion must occur over and the surface area available In most cases, there is a very thin membrane for the gases to cross which is accomplished easily However, under clinical conditions such as pneumonia (infection causing fluid build up in the alveoli themselves), gas exchange is impaired Gas Exchange Two important aspects of gas exchange in the lung are ventilation and perfusion Ventilation is the movement of air into and out of the lungs Perfusion is the flow of blood in the pulmonary capillaries RED = Max Flow Gas Exchange Ventilation is regulated by the diameter of the airways Perfusion is regulated by the diameter of the blood vessels The diameter of the bronchioles is sensitive to the partial pressure of CO2 and O2 in the alveoli Greater CO2 (or Reduced O2) levels in the alveoli causes the bronchioles to increase their diameter which allows CO2 (and O2) to be exchanged at a greater rate A reduced blood O2 level will constrict the pulmonary arteriole and decrease blood flow to increase transit time enabling more gas exchange to occur Gas Exchange Atmospheric4air: PO2 =41594mmHg CO 2 exhaled PCO2 =40.34mmHg O 2 inhaled Pulmonary$ventilation$ (breathing) Gas exchange occurs at two sites in the Alveoli CO 2 O 2 Alveolar4air: PO2 =41054mmHg body: PCO2 =4404mmHg Pulmonary4 CO 2 O2 In the lungs, where O2 is picked up capillaries (a)$External$(pulmonary)$ and CO2 is released at the respiration respiratory membrane (External Respiration) Deoxygenated4blood: PO2 =4404mmHg Oxygenated4blood: PO2 =41004mmHg PCO2 =4454mmHg PCO2 =4404mmHg At the tissues, where O2 is released and CO2 is picked up (internal (b)$Internal$ Respiration) (tissue)respiration At both locations gas exchange occurs Systemic4 CO 2 capillaries O2 due to simple diffusion CO 2 O2 Systemic4tissue4cells: PO2 =4404mmHg PCO2 =4454mmHg Gas Exchange Atmospheric4air: PO2 =41594mmHg CO 2 exhaled PCO2 =40.34mmHg O 2 inhaled Pulmonary$ventilation$ (breathing) External Respiration Alveoli CO 2 O 2 Alveolar4air: PO2 =41054mmHg PCO2 =4404mmHg The partial pressure of O2 in the alveoli is ~105 mmHg, whereas its partial pressure in the CO 2 Pulmonary4 capillaries O2 capillary blood is ~40 mmHg (a)$External$(pulmonary)$ respiration This very strong pressure gradient causes O2 to rapidly cross the respiratory membrane and enter the blood Deoxygenated4blood: PO2 =4404mmHg Oxygenated4blood: PO2 =41004mmHg The partial pressure of CO2 in the alveoli is ~40 PCO2 =4454mmHg PCO2 =4404mmHg mmHg, whereas its partial pressure in the capillary blood is ~45 mmHg (b)$Internal$ (tissue)respiration The high solubility of CO2 (despite the small pressure gradient) causes CO2 to rapidly CO 2 Systemic4 capillaries O2 cross the respiratory membrane and enter the alveoli CO 2 O2 Systemic4tissue4cells: PO2 =4404mmHg PCO2 =4454mmHg Gas Exchange Atmospheric4air: PO2 =41594mmHg CO 2 exhaled PCO2 =40.34mmHg O 2 inhaled Pulmonary$ventilation$ (breathing) Internal Respiration Alveoli CO 2 O 2 Alveolar4air: PO2 =41054mmHg PCO2 =4404mmHg The partial pressure of O2 in the tissues is ~40 mmHg, whereas its partial pressure in the CO 2 Pulmonary4 capillaries O2 arterial blood is ~100 mmHg (a)$External$(pulmonary)$ respiration This very strong pressure gradient causes O2 to rapidly cross the plasma membrane and enter the tissues Deoxygenated4blood: PO2 =4404mmHg Oxygenated4blood: PO2 =41004mmHg The partial pressure of CO2 in the tissues is ~45 PCO2 =4454mmHg PCO2 =4404mmHg mmHg, whereas its partial pressure in the arterial blood is ~40 mmHg (b)$Internal$ (tissue)respiration The high solubility of CO2 (despite the small pressure gradient) causes CO2 to rapidly CO 2 Systemic4 capillaries O2 cross the plasma membrane and enter the blood CO 2 O2 Systemic4tissue4cells: PO2 =4404mmHg PCO2 =4454mmHg KNES 323: Integrative Physiology Respiratory 3 Monday October 21, 2024 Class Outline 1. O2 Transport 2. O2-Hb Dissociation Curve 3. CO2 Transport 4. Exercise Oxygen Transport Oxygen Transport Transport)of)CO 2 7%#dissolved#in#plasma 23%#as#Hb3CO 2 70%#as#HCO 3– Transport)of)O 2 1.5%#dissolved#in#plasma 98.5%#as#Hb3O 2 Alveoli CO2 O2 In order for the exchange of O2 70% 23% 7% 1.5% 98.5% and CO2 to occur, both gases CO2 +#Hb O2 Hb +#O2 CO2 Hb Erythrocyte Hb–CO2 (dissolved) (dissolved) Hb–O2 must be transported between HCO3– Pulmonary#circulation the-external and internal respiration sites Both gases require specialized transport systems for the majority of the gas molecules Systemic#circulation to be moved between the lungs HCO3– and other tissues Hb–CO2 CO2 Hb–O2 O2 (dissolved) Hb (dissolved) O2 Hb 70% 23% 7% 1.5% Systemic CO2 tissue#cells O2 Oxygen Transport Transport)of)CO 2 7%#dissolved#in#plasma 23%#as#Hb3CO 2 70%#as#HCO 3– Transport)of)O 2 1.5%#dissolved#in#plasma 98.5%#as#Hb3O 2 Alveoli CO2 The majority (~98.5%) of O2 O2 70% 23% 1.5% 98.5% 7% molecules are transported CO2 +#Hb O2 Hb +#O2 CO2 Hb Erythrocyte Hb–CO2 (dissolved) (dissolved) Hb–O2 HCO3– by the hemoglobin of the Pulmonary#circulation erythrocytes There is also a small amount (~1.5%) of O2 (for chemreprea which dissolves in the Central- Con detection Systemic#circulation blood and is transported periphera Or = HCO3– directly in the bloodstream detection Hb–CO2 CO2 Hb–O2 O2 (dissolved) Hb (dissolved) O2 Hb 70% 23% 7% 1.5% Systemic CO2 tissue#cells O2 Oxygen Transport iron -has Heme is the portion of hemoglobin that contains iron, and it is heme that binds O2 Each hemoglobin molecule ECO contains four iron ions, and because of this, each hemoglobin molecule is capable of carrying up to four O2 molecules at a time  Oxygen Transport Hemoglobin is composed of four subunits and forms a quaternary protein structure Each subunit is arranged in aEring-like fashion, with an iron atom covalently bound to the heme in the center of the subunit When oxygen binds to hemoglobin, it becomes oxyhemoglobin Oxygen Transport Binding of the first O2 molecule at the alveoli causes a conformational change in hemoglobin which allows the second molecule of O2 to bind more readily As each molecule of O2 is bound, it further facilitates the binding of the next molecule, until all four heme sites are occupied by O2 O Oxygen Transport The opposite occurs at the tissues as well: After the first O2 molecule dissociates and is “dropped off” at the tissues, the next O2 molecule dissociates more readily helping facilitate internal respiration Oxygen Transport When all four heme sites are occupied, the hemoglobin is said to be saturated (100%) When one to three heme sites are occupied, the hemoglobin is said to be partially saturated The overall hemoglobin saturation level considers the blood as a whole, and refers to the percent of the available heme units bound to O2 at a any given time Oxygen-Hemoglobin Dissociation Curve O2-Hb Dissociation Curve ↑ Por ↑saturation = of henoglobin Partial pressure is an & important aspect of the Deoxygenated*blood (contracting*skeletal*muscle) binding of oxygen to and Deoxygenated*blood Oxygenated*blood disassociation from heme in*systemic*veins (average*at*rest) in*systemic*arteries - Percent*saturation*of*hemoglobin An oxygen–hemoglobin dissociation curve is a graph describing the relationship of partial pressure to the binding of O2 to heme and its subsequent dissociation from heme P****(mmHg) O2 O2-Hb Dissociation Curve Key points to remember: Deoxygenated*blood (contracting*skeletal*muscle) Gases diffuse from higher to lower Deoxygenated*blood Oxygenated*blood partial pressures in*systemic*veins in*systemic*arteries Affinity of an O2 molecule for heme (average*at*rest) increases as more O2 molecules are Percent*saturation*of*hemoglobin bound - Therefore, in the O2-Hb sat curve, as the partial pressure of O2 increases, there is a proportionately greater number of O2 bound to heme The sigmoidal curve also shows the lower the partial pressure of O2, the fewer O2 molecules are bound to heme P****(mmHg) O2  O2-Hb Dissociation Curve These mechanisms underlying the O2-Hb sat curve also function as automatic control mechanisms for regulating how much O2 is delivered to different tissues throughout the body The partial pressure of O2 inside arteries and capillaries is ~100 mmHg Highly active tissues (exercising muscle),E rapidly use O2 to produce ATP, lowering the partial pressure of O2 in the tissue to ~20 mmHg Less active tissue (adipose) has higher partial pressure of O2 in the tissue to ~55-60 mmHg ↑ The partial pressure of O2 inside veins is ~40 mmHg - O2-Hb Dissociation Curve Low'temperature (20°C,'68°F) Factors other than partial pressure also affect the O2-Hb sat curve Percent'saturation'of'hemoglobin Higher temperature promotes hemoglobin and O2 to dissociate faster, whereas a lower Normal'blood temperature inhibits dissociation temperature (37°C,'98.6°F) Typically, this has little impact as the human body tightly regulates temperature High'temperature One exception is in highly active tissues (43°C,'110°F)' (exercising muscle), which can release a large amount of heat This increases the ability for O2 to dissociates from hemoglobin which helps provide active tissues with more O2 P''''(mmHg) O2 O2-Hb Dissociation Curve Certain hormones (androgens, epinephrine, thyroid / growth hormone) can affect the O2-Hb sat curve by stimulating the production of 2,3- diphosphoglycerate (DPG) by erythrocytes DPG is a byproduct of glycolysis and since erythrocytes do not have mitochondria, glycolysis is how they produce ATP Elevated DPG promotes the disassociation of O2 from hemoglobin O2-Hb Dissociation Curve Blood pH is another factor influencing the O2-Hb sat curve ↑ High%blood%pH Low'blood The Bohr effect is a phenomenon that arises (7.6) P'''' CO from the relationship between pH and O2’s 2 Percent%saturation%of%hemoglobin Percent'saturation'of'hemoglobin affinity for hemoglobin: Normal%blood%pH Normal'blood (7.4) P A lower pH (acidic) promotes O2 dissociation CO2 from hemoglobin Low%blood%pH High'blood' A higher pH (basic) inhibits O2 dissociation (7.2) PCO2 from hemoglobin Furthermore, blood pH may become more acidic with certain byproducts of cell metabolism (ATP hydrolysis, carbonic acid, and CO2) are released P%%%%(mmHg) OP''''(mmHg) 2O 2 (a)%Effect%of%pH%on%affinity%of%hemoglobin%for%oxygen (b)'Effect'of'PCO on'affinity'of'hemoglobin'for'oxygen 2  O2-Hb Dissociation Curve Summary Low'temperature (20°C,'68°F) difficult High%blood%pH to (7.6) bind Percent%saturation%of%hemoglobin ↓ Percent'saturation'of'hemoglobin Normal%blood%pH Normal'blood temperature (7.4) (37°C,'98.6°F) Low%blood%pH High'temperature (7.2) (43°C,'110°F)' P%%%%(mmHg) O2 P''''(mmHg) O2 (a)%Effect%of%pH%on%affinity%of%hemoglobin%for%oxygen -easy to bird Low'blood P'''' CO2 Percent'saturation'of'hemoglobin Normal'blood PCO 2 High'blood' PCO 2 - difficult to bird P''''(mmHg) O2 (b)'Effect'of'PCO on'affinity'of'hemoglobin'for'oxygen 2 O2-Hb Dissociation Curve Summary https://www.youtube.com/watch?v=vj8c2jiYI2g Carbon Dioxide Transport CO2 Transport CO2 is transported by three major mechanisms: Transport in the form of bicarbonate (HCO3–), which also dissolves in plasma CO2 transport is by blood plasma, as some CO2 molecules dissolve in the blood CO2 transport bound to hemoglobin on erythrocytes  CO2 Transport Transport)of)CO 2 7%#dissolved#in#plasma 23%#as#Hb3CO 2 70%#as#HCO 3– Transport)of)O 2 1.5%#dissolved#in#plasma 98.5%#as#Hb3O 2 Alveoli Majority (~70%) of the CO2 molecules CO2 O2 from the tissues diffuses into the blood 70% 23% 1.5% 98.5% 7% and is transported to the lungs as CO2 +#Hb O2 Hb +#O2 CO2 Hb Erythrocyte Hb–CO2 (dissolved) (dissolved) Hb–O2 bicarbonate HCO3– Pulmonary#circulation Most bicarbonate is produced in erythrocytes after CO2 diffuses into the capillaries, and subsequently into the Carbonic erythrocytes COLtH20 Anhidress s HeCoz ↓ Carbonic anhydrase (CA) causes CO2 and (HCOst 1) H2O to form carbonic acid (H2CO3), - + which dissociates into two ions: Systemic#circulation Bicarbonate (HCO3–) and Hydrogen HCO3– (H+) - Hb–CO2 CO2 Hb–O2 O2 (dissolved) Hb (dissolved) O2 Hb 70% 23% 7% 1.5% Systemic CO2 tissue#cells O2  CO2 Transport HCO3- tends to build up in the erythrocytes, Chloride shift which results in a - greater concentration of Cl$– Cl – CO2$ +$Hb Hb–CO2$+ O2 HCO3- in the erythrocytes than in the CO2 CO2 CO2 CO2$ +$H2O Carbonic)anhydrase H2CO3 HCO3– +$H+ surrounding blood plasma O2 O2 HCO3– O2 O2$ +$Hb–H Hb–O2 Some of the HCO3- will leave the Interstitial fluid Plasma erythrocytes and move down its Tissue$cell Red$blood$cell Systemic concentration gradient into the8 capillary$wall plasma in (b)$Exchange$of$O2 and$CO2 in$systemic$capillaries$(internal$respiration) exchange for chloride (Cl–) ions This phenomenon is referred to as the chloride shift and occurs because by exchanging one - negative ion for another negative ion, neither the electrical charge of the erythrocytes nor that of the blood is altered  capillaries lungs CO2 Transport tissue CO COLO-HrCOEKL05 At the pulmonary capillaries, the Chloride chemical reaction that produced HCO3- is shift Cl$– Cl – CO2$ +$Hb Hb–CO2$+ O2 reversed, and CO2 and H2O are the CO2 CO2 CO2 CO2$ +$H2O Carbonic)anhydrase H2CO3 HCO3– +$H+ products O2 O2 HCO3– O2 O2$ +$Hb–H Hb–O2 H+ ions and HCO3- join to form Interstitial Plasma fluid Tissue$cell Red$blood$cell carbonic acid, which is converted into Systemic capillary$wall CO2 and H2O by carbonic anhydrase (b)$Exchange$of$O2 and$CO2 in$systemic$capillaries$(internal$respiration) The CO2 is then able to diffuse out of the Reverse erythrocytes into the plasma, across the Exhaled chloride shift CO2$ +$Hb Hb–CO2 respiratory membrane into the alveoli CO2 CO2 Cl – CO2 Cl$– CO2$ +$H2O Carbonic)anhydrase H2CO3 HCO3– +$H+ where it is expelled into the atmosphere O2 O2 HCO3– O2 O2$ +$Hb–H Hb–O2+$H+ Interstitial Plasma Inhaled fluid Red$blood$cell Alveolus Pulmonary capillary$wall (a)$Exchange$of$O2 and$CO2 in$pulmonary$capillaries$(external$respiration) CO2 Transport Transport)of)CO 2 7%#dissolved#in#plasma 23%#as#Hb3CO 2 70%#as#HCO 3– Transport)of)O 2 1.5%#dissolved#in#plasma 98.5%#as#Hb3O 2 Alveoli CO2 Although CO2 is not considered to be O2 70% 23% 1.5% 98.5% 7% highly soluble in blood, a small CO2 +#Hb CO2 Hb O2 Hb +#O2 (dissolved) Hb–O2 Erythrocyte fraction of CO2 (~7%) diffuses into the Hb–CO2 (dissolved) HCO3– blood from the tissues and dissolves in - Pulmonary#circulation plasma The dissolved CO2 travels from the tissues in the bloodstream to the pulmonary capillaries G The dissolved CO2 readily diffuses across the respiratory membrane Systemic#circulation into the alveoli and is exhaled HCO3– Hb–O2 during pulmonary ventilation - Hb–CO2 CO2 O2 (dissolved) Hb (dissolved) O2 Hb 70% 23% 7% 1.5% Systemic CO2 tissue#cells O2 CO2 Transport Transport)of)CO 2 7%#dissolved#in#plasma 23%#as#Hb3CO 2 70%#as#HCO 3– Transport)of)O 2 1.5%#dissolved#in#plasma 98.5%#as#Hb3O 2 Alveoli CO2 O2 Some CO2 (~23%) is able to be 70% 23% 1.5% 98.5% 7% CO2 +#Hb transported to the lungs bound CO2 Hb O2 Hb +#O2 Erythrocyte Hb–CO2 (dissolved) (dissolved) Hb–O2 to hemoglobin - HCO3– Pulmonary#circulation In contrast to O2, CO2 does not bind to the iron ions, instead CO2 binds to amino acids on the globin portions of hemoglobin to form carbaminohemoglobin Systemic#circulation Only occurs when Hb and CO2 HCO3– bind Hb–CO2 Hb CO2 (dissolved) Hb O2 (dissolved) Hb–O2 O2 70% 23% 7% 1.5% Systemic CO2 tissue#cells O2 CO2 Transport Atmospheric4air: PO2 =41594mmHg CO 2 exhaled PCO2 =40.34mmHg O 2 inhaled Pulmonary$ventilation$ (breathing) Because CO2 is expelled at the lungs, Alveoli CO 2 O Alveolar4air: blood leaving the lungs has a lower partial 2 PO2 =41054mmHg PCO2 =4404mmHg pressure of CO2 than is found in the - Pulmonary4 CO 2 O2 tissues capillaries (a)$External$(pulmonary)$ CO2 leaves the tissues due to its higher respiration partial pressure, enters the blood, and then moves into erythrocytes and binds Deoxygenated4blood: Oxygenated4blood: to hemoglobin PO2 =4404mmHg PCO2 =4454mmHg PO2 =41004mmHg PCO2 =4404mmHg In the pulmonary capillaries, there is a higher partial pressure of CO2 compared (b)$Internal$ (tissue)respiration to the alveoli CO2 dissociates from hemoglobin and Systemic4 CO 2 capillaries O2 diffuses across the respiratory membrane is expelled CO 2 O2 Systemic4tissue4cells: PO2 =4404mmHg PCO2 =4454mmHg O2 and CO2 Transport ↑ saturation hemoglobin = ↓ affinity of CO2 The Haldane effect is a phenomenon that arises from the relationship between the partial pressure of O2 and the affinity of hemoglobin for CO2 Hemoglobin saturated with O2 does not readily bind CO2 When O2 is not bound to heme AND the partial pressure of O2 is low, hemoglobin will readily bind CO2 O2 and CO2 Transport https://www.youtube.com/watch?v=8-jiIBrgD1I Exercise Exercise At rest, the respiratory system performs its functions at a0constant, rhythmic pace, as regulated by the respiratory - centers of the brain Under these conditions ventilation provides sufficient O2 to body tissues However, there are times the respiratory system alters the pace of its functions in order to accommodate the adjusted O2 demands of the body Exercise Hyperpnea is an increased depth (and rate) of ventilation to meet an-increase in O2 demand as might be seen in exercise or certain respiratory diseases & Hyperventilation on the other hand is an increased ventilation depth and rate independent of the cellular O2 needs and leads to abnormally low blood CO2 - levels and high blood pH (alkaline) Exercise Steady-State Exercise Initially, there can be a small anticipatory increase in ventilation (possibly due to psychological stimuli) As exercise is initiated, there is a steep rise in ventilation as a result of the afferent feedback from the body to the cardiorespiratory centres in the brain affrent exercise > -- cardiorespiratory > - Centres ↓ ↑entilation depthrate Exercise Steady-State Exercise There is then a slower increase in ventilation as the body fine tunes the ventilatory response to match the bodies needs After a few minutes the body is able to get into steady-state with ventilation stable to meet the body’s needs (hyperpnea) Once exercise is completed there is a fast decline in respiration until the “new” resting steady-state needs are met Exercise ↑CO2 while doe = hypercentilationa Maximal Exercise Test Below VT1 we are below aerobic threshold, and the increased ventilation meets our metabolic demands - via hyperpnea After VT1 our bodies into anaerobic metabolism and are producing more CO2 than the O2 we are consuming so we hyperventilate to try and expel - the excess CO2 (aerobic threshold) Exercise ↓ O2 compared to NO2 demand= Thypenenla e Maximal Exercise Test When we hit VT2 we are - nearing the point of exhaustion and there is a further increase in ventilation as we try and get every bit of O2 we can (anaerobic threshold)