1Chapter 10:Respiration During ExerciseIntroduction• The Respiratory System– Provides a means of gas exchange between the environment and the body– Plays a role in the regulation of acid-base balance during exerciseObjectives• Explain the principle physiological function of the pulmonary system• Outline the major anatomical components of the respiratory system• List major muscles involved in inspiration & expiration at rest & during exercise• Discuss the importance of matching blood flow to alveolar ventilation in the lung• Explain how gases are transported across the blood-gas interface in the lungObjectives• Discuss the major transportation modes of O2& CO2in the blood• Discuss the effects of ↑ temp, ↓ pH, & ↑ levels of 2,3 DPG on the oxygen-hemoglobin dissociation curve• Describe the ventilatory response to constant load, steady-state exerciseObjectives• Describe the ventilatory response to incremental exercise• Identify the location & function of chemoreceptors and mechanoreceptors that are thought to play a role in the regulation of breathing• Discuss the neural-humoral theory of respiratory control during exerciseRespiration1. Pulmonary respiration– Ventilation (breathing) and the exchange of gases (O2& CO2) in the lungs2. Cellular respiration– Relates to O2 utilization and CO2production by the tissues• This chapter is concerned with pulmonary respiration.2Function of the Lungs• Primary purpose is to provide a means of gas exchange between the external environment and the body• Ventilation refers to the mechanical process of moving air into and out of lungs• Diffusion is the random movement of molecules from an area of high concentration to an area of lower concentrationMajor Organs of the Respiratory SystemFig 10.1Position of the Lungs, Diaphragm, and Pleura-VisceralParietalFig 10.2Conducting and Respiratory ZonesConducting zone• Conducts air to respiratory zone• Humidifies, warms, and filters air• Components:– Trachea– Bronchial tree– BronchiolesRespiratory zone• Exchange of gases between air and blood• Components:– Respiratory bronchioles– Alveolar sacsConducting & Respiratory ZonesFig 10.2Respiratory Airways• 16 generations– Conducting airways– Bulk flow (water hose)– X-sections reduces forward velocity• 7 generations– Transitional zone– Respiratory zone–Diffusion3Alveolar Sites• Large surface area for gas exchange• Minimal diffusion distance• Alveolar and capillary walls-large lipid content•O2diffuses, not H2O• X-sectional area – 500-1000 ft2Respiratory Zone• Alveoli– Site of gas exchange from external respiration– Extensive capillarization in alveoli walls– Blood gas barrier (2 cell layers thick)• Lung diffusionDiffusion• Concentration gradient• Minimal distance– Smoking effectsPathway of Air to AlveoliFig 10.4Mechanics of Breathing• Ventilatory muscles cause the size variations in the thoracic cavity• Inspiration– Diaphragm pushes downward, lowering intrapulmonary pressure• Expiration– Diaphragm relaxes, raising intrapulmonary pressure• Resistance to airflow – Largely determined by airway diameterThe Mechanics of Inspiration and ExpirationFig 10.64Mechanics of Breathing• Inspiratory muscles– 1. Diaphragm• Contraction occurs when rt and ltphrenic nerve stimulated• Flattens and makes thoracic cavity longerMechanics of Breathing• Inspiratory muscles– 2. External intercostals• Contraction lifts ribs• Increases transverse diameter• Increase in thoracic size accompanied by decrease in intrathoracic pressure• Air moves from high pressure to low pressureMechanics of Breathing• Expiration (rest)– Diaphragm and intercostals relax (passive)– Thoracic cavity returns to original size– Intrapulmonary pressure > ambient– Air flows outward to atmosphereMechanics of Breathing• Expiration (exercise)– Expiratory muscles• Abdominal group• Internal intercostals– Action• Lower ribs, moves them closer together• Facilitates expiration (active)Ventilatory MusclesMuscles of RespirationFig 10.75Pulmonary Ventilation (V)• The amount of air moved in or out of the lungs per minute– Product of tidal volume (VT) and breathing frequency (f)V = VTx fPulmonary Ventilation (V)• Dead-space ventilation (VD)– “unused” ventilation– Does not participate in gas exchange– Anatomical dead space: conducting zone– Physiological dead space: disease• Alveolar ventilation (VA)– Volume of inspired gas that reaches the respiratory zoneV = VA+ VDPulmonary Volumes and Capacities• Measured by spirometry• Vital capacity (VC)– Maximum amount of air that can be expired following a maximum inspiration• Residual volume (RV)– Air remaining in the lungs after a maximum expiration• Total lung capacity (TLC)– Sum of VC and RVPulmonary Volumes and Capacities• Tidal Volume– Volume of air inspired or expired per breath• Inspiratory Reserve Volume (IRV)– Volume of air that can be inspired after a normal inspirationPulmonary Volumes and Capacities• Inspiratory Capacity (IC)– Volume of air inspired from rest to maximal inspiration–TV + IRV• Functional Residual Capacity (FRC)– Volume of air in lungs at rest • Expiratory Reserve Volume (ERV)– Volume of air that can be expired after a normal expirationPulmonary Volumes and CapacitiesFig 10.96Lung Disease• Obstructive lung disease– COPD and asthma• Narrowing of airways• Restrictive lung disease– Fibrosis Partial Pressure of GasesDalton’s Law• The total pressure of a gas mixture is equal to the sum of the pressure that each gas would exert independently• The partial pressure of oxygen (PO2)– Air is 20.93% oxygen• Expressed as a fraction: 0.2093– Total pressure of air = 760 mmHgPO2 = 0.2093 x 760 = 159 mmHgPartial Pressure and Gas ExchangeFig 10.10Blood Flow to the Lung• Pulmonary circuit– Same rate of flow as systemic circuit– Lower pressureFig 10.11Blood Flow to the Lung• When standing, most of the blood flow is to the base of the lung– Due to gravitational forceFig 10.12Ventilation-Perfusion Relationships• Ventilation/perfusion ratio– Indicates matching of blood flow to ventilation– Ideal: ~1.0•Base– Overperfused (ratio <1.0)– Greater blood flow than ventilation• Apex– Underperfused (ratio >1.0)– Less blood flow than ventilation7Ventilation/Perfusion RatiosFig 10.13O2Transport in the Blood•