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Oxygen Transport
 within the blood it is achieved in two ways:
1) a small amount of oxygen is dissolve within the plasma or the fluid
component of blood
2) binds to a specialized protein called hemoglobin
Carbon Dioxide Transport
 it must be removed from body tissues, where it is produced, then
back to the lungs where it can be moved into the alveoli and then
exhaled and removed from the body
 3 ways in which carbon dioxide is carried within the blood:
1) a small amount of CO2 is found dissolved in the plasma
 5 – 10% of CO2 is transported dissolved in the plasma
 90 – 95% of CO2 diffuses into the RBC
2) CO2 can bind to hemoglobin called carbaminohemoglobin (~20%)
 in the lung, elevated concentration of O2 is stimulates hemoglobin to
release CO2 – which diffuses out into the alveoli and is exhaled
3) bicarbonate system (~70 – 75%)
 CO2 diffuses into RBC, but undergoes a chemical reaction with water,
forming a weak acid called carbon acid
 once the chemical reaction occurs CO2 returns to its original form, it is
free to diffuse out of the blood and into the alveoli which is then
Ventilation and the Regulation of Blood pH
 ventilation plays an important role in regulation of the pH in the
blood - blood pH is a measure of how acidic or how basic the blood
 during exercise, large amounts of acid (lactic acid) are released into
the blood which results in a decline in blood pH
Respiratory Dynamics
 during exercise, the body responds to the increased need of O2 at the
working muscle through a series of responses that match O2 delivery
with O2 demand
 the respiratory system results in changes that occur in pulmonary
ventilation, external respiration and internal respiration
 exercise results in an increase in pulmonary ventilation, external and
internal respiration, and cellular respiration
Pulmonary Ventilation
 it is closely matched to the rate and/or intensity of work being done
 with increases in ventilation at sub-maximal exercise it can be divided
into 3 phases:
 phase 1 – rapid on phase
 ventilation is increasing at a very rapid rate, almost immediately upon
the onset of activity
 phase 2 – slower exponential increase from the rapid increase
observed in phase 1
 phase 3 – leveling off of ventilation at a new steady state level
External Respiration
 total gas exchange at the lungs is increased as a result of 2 factors:
1) increase in ventilation
2) increase in blood flow to the lungs
 the increase in gas exchange is matched to the increase in
requirement of the working skeletal muscle
 the maintenance of diffusion gradients ensures proper oxygenation of
blood and removal of CO2 (figure 7.11, p. 126)
Internal Respiration
 exchange of gases at the level of the tissues – extraction of O2 at the
tissues in increased
 during exercise, skeletal muscle increases cellular respiration, and O2
is used to generate ATP
 an increase in the use of O2 results in a decline in PO2 within the
skeletal muscle, and increase the gradient between PO2 within the
blood and muscle – this enhances the diffusion of O2 out of the blood
to the working muscle
 increase in muscle activity results in an increase in CO2 production, a
decrease in pH, and an increase in temperature
 one way to determine how oxygen has been delivered to skeletal
muscle is to measure to amount of oxygen in the arterial blood
before it arrives at the muscle, then measure the venous blood that
drains from the same muscle
 the difference between the amount of O2 in the artery and vein
reflects the amount of O2 delivered to the muscle – this is termed
a-vO2 difference (figure 7.12, p. 127)