Respiration During Exercise. The Respiratory System. Objectives. Provides a means of gas exchange b/n the env t & the body

Transcription

1 Chapter 10 Respiration During Exercise The Respiratory System Provides a means of gas exchange b/n the env t & the body Plays a role in the regulation of acid-base balance during exercise Objectives 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 lung 1

2 Objectives Discuss the major transportation modes of O 2 & CO 2 in the blood Discuss the effects of temp, ph, & levels of 2,3 DPG on the oxygenhemoglobin dissociation curve Describe the ventilatory response to constant load, steady-state exercise Objectives 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 exercise Respiration 1. Pulmonary respiration Ventilation (breathing) and the exchange of gases (O 2 & CO 2 ) in the lungs 2. Cellular respiration Relates to O 2 utilization and CO 2 production by the tissues This chapter is concerned with pulmonary respiration, and respiration will be used to mean such 2

3 Respiration Function of the Lungs 1 purpose is to provide a means of gas exchange b/n the external env t & the body Major Organs of the Respiratory System 3

4 Position of the Lungs, Diaphragm & Pleura Conducting & Respiratory Zones Conducting zone Respiratory zone Conducting & Respiratory Zones 4

5 Pathway of Air to Alveoli Mechanics of Breathing Ventilation Inspiration Expiration Resistance to airflow The Mechanics of Inspiration & Expiration 5

6 Muscles of Respiration Pulmonary Ventilation (VE) Pulmonary Ventilation (VE) Dead-space ventilation (V D ) unused ventilation Does not participate in gas exchange Anatomical dead space: conducting zone Physiological dead space: disease Alveolar ventilation (V A ) Volume of inspired gas that reaches the respiratory zone V = V A + V D 6

7 Pulmonary Volumes & 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 & RV A Spirogram Showing Pulmonary Volumes & Capacities Partial Pressure (PP) of Gases Dalton s Law The total pressure of a gas mixture is equal to the sum of the pressure that each gas would exert independently The PP of O 2 (PO 2 ) Air is 20.93% oxygen Expressed as a fraction: Total pressure of air = 760 mmhg PO 2 = x 760 = 159 mmhg 7

8 Diffusion of Gases Fick s law of diffusion The rate of gas transfer ( V gas) is proportional to the tissue area, the diffusion coefficient of the gas, and the difference in the partial pressure of the gas on the two sides of the tissue, and inversely proportional the the thickness. V gas = A T x D x (P 1-P 2 ) V gas = rate of diffusion A = tissue area T = tissue thickness D = diffusion coefficient of gas P 1 -P 2 = difference in partial pressure Diffusion of Gases PP & Gas Exchange 8

9 Blood Flow to the Lung Pulmonary circuit Blood Flow to the Lung When standing, most of the blood flow is to the base of the lung Ventilation-Perfusion Relationships Ventilation/perfusion ratio Indicates matching of blood flow to ventilation Ideal: ~1.0 Base Overperfused (ratio <1.0) Apex Underperfused (ratio >1.0) 9

10 Ventilation/Perfusion Ratios O 2 Transport in the Bld O 2 Hb Dissociation Curve 10

11 O 2 -Hb Dissociation Curve: Effect of ph O 2 -Hb Dissociation Curve: Effect of T O 2 -Hb Dissociation Curve: 2-3 DPG 11

12 O 2 Transport in Muscle Dissociation Curves for Mb & Hb CO 2 Transport in Bld 12

13 CO 2 Transport in Bld Release of CO 2 From Bld Rest-to-Work Transitions 13

14 Exercise in a Hot Env t Incremental Exercise Ventilatory Reponse to Exercise: Trained vs. Untrained In the trained runner 14

15 Ventilatory Reponse to Exercise: Trained vs. Untrained Control of Ventilation Respiratory control center Receives neural and humoral input Input to the Respiratory Control Centers Humoral chemoreceptors Central chemoreceptors Peripheral chemoreceptors Neural input 15

16 Effect of Arterial PCO 2 on VE Effect of Arterial PO 2 on VE Ventilatory Control During Exercise Submaximal exercise 16

17 Ventilatory Control During Submaximal Exercise Effect of Training on VE VE is lower at same work rate following training Effects of Endurance Training on VE During Exercise 17

18 Do the Lungs Limit Exercise Performance? Submaximal exercise Maximal exercise 18