Respiratory System II: Breathing and Gas ExchangeRespiratory Volumes and CapacitiesSlide 3Slide 4Gas Exchanges Between Blood, Lungs, and TissuesBasic Properties of Gases: Dalton’s Law of Partial PressuresBasic Properties of Gases: Henry’s LawComposition of Alveolar GasSlide 9External Respiration DefinedPartial Pressure Gradients and Gas SolubilitiesSlide 12Gas Transport in the BloodOther Factors Influencing Hemoglobin SaturationSlide 15Homeostatic ImbalanceHypoxia, Cyanosis, and CO PoisioningExternal Vs Internal RespirationSlide 19Neural Regulation of RespirationRespiratory Disorders: Chronic Obstructive Pulmonary Disease (COPD)Respiratory System II: Breathing and Gas Exchange Respiratory Volumes and CapacitiesPartial Pressure and Gas ExchangeGas Transport and Hb CooperativityNeural Control of RespirationRespiratory DisordersRespiratory Volumes and CapacitiesNormal breathing moves about 500 ml of air with each breath (tidal volume [TV])Factors Affecting Respiratory Capacity: Size, Gender, Age, ConditionExpiratory reserve volume (ERV)•Amount of air that can be forcibly exhaled•Approximately 1200 mlInspiratory reserve volume (IRV)•Amount of air that can be taken in forcibly beyond the tidal volume•Usually 2100-3200 mlspirometerRespiratory Volumes and CapacitiesResidual volume•Air remaining in lung after expiration•About 1200 mlRespiratory Rate•Number of cycles/minute•Based on one inspiration and expiration•Normally about 15 cycles/minMinute Ventilation•Tidal volume x respiratory rate (breaths/min)•Volume of air inhaled/exhaled per minute•Normally 5-8 litersRespiratory System II: Breathing and Gas Exchange Respiratory Volumes and CapacitiesPartial Pressure and Gas ExchangeGas Transport and Hb CooperativityNeural Control of RespirationRespiratory DisordersGas Exchanges Between Blood, Lungs, and TissuesExternal respiration (between lungs and outside)Internal respiration (between bloodstream and tissues)To understand the above processes, first consider•Physical properties of gases •Composition of alveolar gasBasic Properties of Gases: Dalton’s Law of Partial PressuresTotal pressure exerted by a mixture of gases is the sum of the pressures exerted by each gas (TP = PPN2 + PPO2 + PPCO2 + PPH2O)The partial pressure of each gas is directly proportional to its percentage in the mixtureBasic Properties of Gases: Henry’s LawWhen a mixture of gases is in contact with a liquid, each gas will dissolve in the liquid in proportion to its partial pressureAt equilibrium, the partial pressures in the two phases will be equalThe amount of gas that will dissolve in a liquid also depends upon its solubility•CO2 is 20 times more soluble in water than O2•Very little N2 dissolves in waterComposition of Alveolar GasAlveoli contain more CO2 and water vapor than atmospheric air, due to•Gas exchanges in the lungs•Humidification of air •Mixing of alveolar gas that occurs with each breathTable 22.4External Respiration DefinedExchange of O2 and CO2 across the respiratory membrane in the lungsInfluenced by•Partial pressure gradients and gas solubilities•Ventilation-perfusion coupling•Structural characteristics of the respiratory membranePartial Pressure Gradients and Gas SolubilitiesPartial pressure gradient for CO2 in the lungs is less steep:•Venous blood Pco2 = 45 mm Hg•Alveolar Pco2 = 40 mm HgCO2 is 20 times more soluble in plasma than oxygenAided also by ventilation-perfusion coupling: where alveolar CO2 is high, bronchioles dilate; where alveolar CO2 is low, bronchioles constrict*Perfusion is the ability of blood to flow through tissues.Partial pressure gradient for O2 in the lungs is steep•Venous blood PO2 = 40 mm Hg•Alveolar PO2 = 104 mm HgO2 quickly diffuses from alveoli to bloodstreamAided also by ventilation-perfusion* coupling: Where alveolar O2 is high, arterioles dilate; where alveolar O2 is low, arterioles constrictRespiratory System II: Breathing and Gas Exchange Respiratory Volumes and CapacitiesPartial Pressure and Gas ExchangeGas Transport and Hb CooperativityNeural Control of RespirationRespiratory DisordersGas Transport in the BloodOxygen transport in the blood•Inside red blood cells attached to hemoglobin (oxyhemoglobin [HbO2])•A small amount (< 2%) is carried dissolved in the plasmaLoading and unloading of O2 is facilitated by change in shape of Hb •As O2 binds, Hb affinity for O2 increases•As O2 is released, Hb affinity for O2 decreasesChange in binding affinity known as positive cooperativityFully (100%) saturated if all four heme groups carry O2Rate of loading and unloading of O2 is regulated by many factorsSigmoidal relationship seen on binding graphIncreasingly steeper line (more saturation) as more oxygen present.Other Factors Influencing Hemoglobin SaturationIncreases in temperature, H+, PCO2, and BPG (bisphosphoglycerate).•They modify the structure of hemoglobin and decrease its affinity for O2 [binding with H+( pH), PCO2,BPG] •Enhanced O2 unloading in the capillaries where higher CO2 concentration lowers pH (increases H+)and facilitates more O2 unloading•Decreases in temp, H+, PCO2, and BPG•Modify Hb structure and in crease O2 affinity•Enhanced loading of O2 at the lungs•[ binding with  H+ ( pH),  PCO2,  BPG]Figure 22.21O2P (mm Hg) Normal bodytemperature10°C20°C38°C43°CNormal arterialcarbon dioxide(P 40 mm Hg)or H+ (pH 7.4) CO2Increased carbon dioxide(P 80 mm Hg)or H+ (pH 7.2)CO2Decreased carbon dioxide(P 20 mm Hg) or H+ (pH 7.6)CO2(a)(b)Changes in O2 Binding Curve with Difft Temps and pHsDecreased bindingIncreased bindingDecreased bindingIncreased bindingp O2 in HgHomeostatic ImbalanceHypoxia (leading to cyanosis)•Inadequate O2 delivery to tissues •A variety of causesoToo few RBCsoAbnormal or too little HboBlocked circulationoMetabolic poisonsoPulmonary diseaseoCarbon monoxideHypoxia, Cyanosis, and CO PoisioningCyanosis of the face Cyanotic nail bedsCherry red skin from carbon monoxide poisoningExternal Vs Internal Respiration• In the lungs, plasma HCO3- and H+ are converted by carbonic anhydrase in the RBC to form carbonic acid which breaks down into CO2 and H2O; CO2 unloaded into alveoli, blood pH rises as H+ removed.•Oxygen diffuses from blood into tissue (acidic conditions favor oxygen