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Chapter 10. Pulmonary Function During Exercise. The Respiratory System. Provides gas exchange between the environment and the body Regulates of acid-base balance during exercise. Ventilation. Moving Air. Conducting zone Conducts air to respiratory zone Humidifies, warms, and filters air - PowerPoint PPT Presentation
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Pulmonary Function During Exercise
Chapter 10
The Respiratory System
Provides gas exchange between the environment and the body
Regulates of acid-base balance during exercise
Ventilation
Moving Air
Conducting and Respiratory Zones
Conducting zone Conducts air to
respiratory zone Humidifies, warms,
and filters air Components:
– Trachea– Bronchial tree– Bronchioles
Respiratory zone Exchange of gases
between air and blood Components:
– Respiratory bronchioles
– Alveolar sacs
Pathway of Air to Alveoli
Mechanics of Breathing
Ventilation– Movement of air into and out of the lungs via bulk
flow Inspiration
– Diaphragm pushes downward, lowering intrapulmonary pressure
Expiration– Diaphragm relaxes, raising intrapulmonary pressure
Resistance to airflow – Largely determined by airway diameter
The Mechanics of Inspiration and Expiration
Pulmonary 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 RV
Pulmonary Volumes and Capacities
Inspiratory Reserve volume (IRV)– Maximum amount of air that can be inspired following a
normal inspiration Expiratory reserve volume (ERV)
– Air remaining in the lungs after a normal expiration
A Spirogram Showing Pulmonary Volumes and Capacities
Check measurements to find:
Norms for body sizes Indications of healthy lung function Indications of diseases/conditions that
affect ventilation– Asthma– Emphysema
Pulmonary Ventilation (VE)
The amount of air moved in or out of the lungs per minute– Product of tidal volume (VT)
and breathing frequency (FB)
– (looks similar to Q = SV x HR? )
VE = VT x FB
.
.
.
Respiration
Movement of gasses
Diffusion of Gases
Gases diffuse from high low partial pressure
– From lungs to blood and back to lungs– From blood to tissue and back to blood
Partial Pressure of Gases
Each gas in a mixture exerts a portion of the total pressure of the gas
The partial pressure of oxygen (PO2)
– Air is 20.93% oxygen• Expressed as a fraction: 0.2093
– If total pressure of air = 760 mmHg, then
PO2 = 0.2093 x 760 = 159 mmHg
Partial Pressure and Gas Exchange
O2 Transport in the Blood
O2 is bound to hemoglobin (Hb) for transport in the blood– Oxyhemoglobin: O2 bound to Hb
Carrying capacity – 201 ml O2•L-1 blood in males
• 150 g Hb•L blood-1 x 1.34 mlO2•g Hb-1
– 174 ml O2•L-1 blood in females
• 130 g Hb•L blood-1 x 1.34 mlO2•g Hb-1
Oxyhemoglobin Dissociation Curve
O2-Hb Dissociation Curve: Effect of pH Blood pH declines during heavy
exercise Results in a “rightward” shift of the
curve– Bohr effect
– Favors “offloading” of O2 to the tissues
O2-Hb Dissociation Curve: Effect of pH
20
1816
1412
10 8 6
4 2
Oxy
gen
Con
tent
(ml O
2 / 1
00 m
l blo
od)
Amount of O2
unloaded
O2-Hb Dissociation Curve: Effect of Temperature Increased blood temperature results in
a weaker Hb-O2 bond Rightward shift of curve
– Easier “offloading” of O2 at tissues
O2-Hb Dissociation Curve: Effect of Temperature
Amountoffloaded
Oxy
gen
Con
tent
(ml O
2 / 1
00 m
l blo
od)
O2 Transport in Muscle
Myoglobin (Mb) shuttles O2 from the cell membrane to the mitochondria
Higher affinity for O2 than hemoglobin
– Even at low PO2
– Allows Mb to store O2
Dissociation Curves for Myoglobin and Hemoglobin
Carbon Dioxide Transport
Not identical to oxygen transport
CO2 Transport in Blood
Dissolved in plasma (10%) Bound to Hb (20%) Bicarbonate (70%)
CO2 + H2O H2CO3 H+ + HCO3-
MuscleNormal Metabolism
binds to HbCarbonic Acid
Bicarbonate
CO2 Transport in Blood
Dissolved in plasma (10%) Bound to Hb (20%) Bicarbonate (70%)
CO2 + H2O H2CO3 H+ + HCO3-
Lung Ventilation
O2 replaces on Hb
CO2 Transport in Blood
Dissolved in plasma (10%) Bound to Hb (20%) Bicarbonate (70%)
CO2 + H2O H2CO3 H+ + HCO3-
– Also important for buffering H+
Muscle
Lung
Intense Exercise
Ventilation
Release of CO2 From Blood
Effect of Respiratory Gases on Ventilation
How do these gasses affect breathing?
Control of Ventilation
Respiratory control center in the brainstem– Regulates respiratory rate– Receives neural and humoral input
• Feedback from muscles
• PO2, PCO2, H+, and K+ in blood
• PCO2 and H+ concentration in cerebrospinal fluid
Effect of Arterial PO2 on Ventilation
Effect of Arterial PCO2 on Ventilation
Ventilation and Acid-Base Balance
Blood pH is regulated in part by ventilation
An increase in ventilation causes exhalation of additional CO2
– Reduces blood PCO2
– Lowers H+ concentration
H+ + HCO3- H2CO3 H2O + CO2
Exhalation
Ventilatory Control During Submaximal Exercise
Incremental Exercise
Linear increase in ventilation – Up to ~50-75% VO2max
Exponential increase beyond this point Ventilatory threshold (Tvent)
– Inflection point where VE increases exponentially
.
.
Ventilatory Response to Exercise:Tvent
Is This Trainable?
Does an endurance trained person breathe less?
Does an endurance trained person need less oxygen?
Effect of Training on Ventilation
Ventilation is lower at same work rate following training– May be due to lower blood lactic acid levels– Results in less feedback to stimulate
breathing
– Well trained produce less CO2 – stim. for breathing
Effects of Endurance Training on Ventilation During Exercise
Ventilatory Response to Exercise:Trained vs. Untrained In the trained runner
– Decrease in arterial PO2 near exhaustion• more oxygen extracted
– pH maintained at a higher work rate• less lactic acid produced – “aerobic metab.”
– Tvent occurs at a higher work rate• lower relative intensity
Ventilatory Response to Exercise:Trained vs. Untrained
Do the Lungs Limit Exercise Performance? Sub maximal exercise
– Pulmonary system not seen as a limitation Maximal exercise
– Not thought to be a limitation in healthy individuals at sea level
– May be limiting in elite endurance athletes
Questions?
End
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