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
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Objectives
• Discuss the major transportation modes of
O2 & CO2 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 (O2 & CO2) in the lungs
2. Cellular respiration
– Relates to O2 utilization and CO2 production
by the tissues
• This chapter is concerned with pulmonary
respiration, and “respiration” will be used
to mean such
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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
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Position of the Lungs,
Diaphragm & Pleura
Conducting & Respiratory
Zones
Conducting zone
Respiratory zone
Conducting & Respiratory Zones
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Pathway of Air to Alveoli
Mechanics of Breathing
• Ventilation
• Inspiration
• Expiration
• Resistance to airflow
The Mechanics of Inspiration &
Expiration
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Muscles of Respiration
Pulmonary Ventilation (VE)
Pulmonary Ventilation (VE)
• 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 zone
V = VA + V D
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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 O2 (PO2)
– Air is 20.93% oxygen
• Expressed as a fraction: 0.2093
– Total pressure of air = 760 mmHg
PO2 = 0.2093 x 760 = 159 mmHg
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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 x D x (P1-P2)
T
V gas = rate of diffusion
A = tissue area
T = tissue thickness
D = diffusion coefficient of gas
P1-P2 = difference in partial pressure
Diffusion of Gases
PP & Gas Exchange
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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)
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Ventilation/Perfusion Ratios
O2 Transport in the Bld
O2Hb Dissociation Curve
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O2-Hb Dissociation Curve:
Effect of pH
O2-Hb Dissociation Curve:
Effect of T
O2-Hb Dissociation Curve:
2-3 DPG
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O2 Transport in Muscle
Dissociation Curves for Mb & Hb
CO2 Transport in Bld
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CO2 Transport in Bld
Release of CO2 From Bld
Rest-to-Work Transitions
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Exercise in a Hot Env’t
Incremental Exercise
Ventilatory Reponse to Exercise:
Trained vs. Untrained
• In the trained runner
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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
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Effect of Arterial PCO2 on VE
Effect of Arterial PO2 on VE
Ventilatory Control During Exercise
• Submaximal exercise
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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
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Do the Lungs Limit Exercise
Performance?
• Submaximal exercise
• Maximal exercise
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