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Respiratory Dynamics
7.3
Red Blood Cells
• Also called erythrocytes
• The primary function is to transport oxygen from
the lungs to the tissues and remove carbon
dioxide from the body. They are able to do this
because of a substance called hemoglobin.
• Other components of blood include white blood
cells and the clear fluid plasma. The percentage
of the blood made up of red blood cells is called
hematocrit (about 45%).
The Red Blood Cell
• Single red blood cell or erythrocyte
Hemoglobin
• A molecule made up of proteins and iron
• Each molecule can bond to and transport four oxygen molecules.
• The amount of oxygen that is carried by the blood is dependent
upon the partial pressure of oxygen (PO2).
• The difference in the amount of oxygen that is present in the
blood as it leaves the lungs and the amount of oxygen that is
present in the blood when it returns to the lungs is called the
arterial-venous oxygen difference (a-v O2 difference),
measured in ml of oxygen per litre of blood (ml O2 / L )
• If the a-v O2 difference increases, it means that the body is using
more oxygen.
• The typical a-v O2 difference at rest is about 4 to 5 ml O2 / L,
while during exercise the a-v O2 difference can increase to 15 mL
O2 / L.
Blood
• New red blood cells or reticulocytes are produced in the
bone marrow
• Erythropoietin (EPO), a circulating hormone, is the
principal factor that stimulates red blood cell formation
• EPO is secreted in response to low oxygen levels (when
one goes to altitude) and also in response to exercise,
thus increasing the percentage of new red blood cells in
the body
• New red blood cells contain more hemoglobin than older
red blood cells and thus can carry greater amounts of
oxygen
Testing for Maximal Oxygen Uptake
• Testing maximal aerobic power (VO2max)
Oxygen Uptake
• Changes in hematocrit (concentration of red
blood cells in the blood) can also alter the oxygen
uptake by increasing or decreasing the amount of
oxygen that is supplied to working tissues.
• The ability of the tissues to extract oxygen (a-vO2
difference) directly affects the oxygen uptake.
• Increases in a-vO2 difference may arise due to an
increased number of mitochondria in the
muscles, or increased enzyme efficiency in
working tissues
Oxygen Uptake
• Increased capillarization (number of capillaries
in tissue) can affect the ability of the circulatory
system to place red blood cells close to the
tissues that are using the oxygen.
• As a result, this increases the ability of those
tissues to extract the required oxygen due to a
shorter diffusion distance.
Cardiovascular Anatomy Summary
VO2max = Cardiac Output x (a-vO2) difference
• The central component primarily concerns the
effectiveness of the heart and the peripheral factors
include;
1. the ability of the lungs to oxygenate the blood
2. the ability of the body to extract that oxygen.
• Training can increase the maximal oxygen consumption of
the human body. How this is accomplished will be
presented in the next section.
• http://www.youtube.com/watch?v=i7kn3mkO7Ec
Exercise Effects on the Cardiovascular
and Respiratory Systems
• The cardiovascular system ensures that
adequate blood supply to working
muscles, the brain and the heart is
maintained.
• Also, heat and waste products generated
by the muscles are dissipated and
removed.
Aerobic Training Effect on the
Cardiovascular and Respiratory Systems
Exercise Events: Onset
• VE increases relative to amount of work.
ATP-PC and lactic acid fermentation
occur, cellular respiration begins.
• VE increases rapidly ~65-85% of max
output at a point called the ventilatory
threshold. This corresponds to increase
blood lactic acid and O2 deficit.
Lactate Threshold
Exercise Events: Duration:
• VE levels off to a steady state plateau.
Exercise Events: Recovery:
• VE remains high and gradually lowers to
replenish depleted levels in the body and
return the body to a rest state.
• Training can increase the ventilatory
threshold level, cause the steady-state to
be reached more quickly and decrease
recovery time.
Exercise Effects on the Cardiovascular
and Respiratory Systems cont.
Cardiac Output
• Increase in heart size is one of the
benefits that may arise as a result of
endurance training.
1. Larger atria and ventricles allow for a
greater volume of blood to be pumped
each time the heart beats.
2. Increased thickness of the walls of the
heart (cardiac muscle) allows for
increased contractility (rate of
contraction)
Exercise Effects on the Cardiovascular
and Respiratory Systems cont.
Capillary Supply
•
Increased capillarization is another benefit that
may arise as a result of endurance training.
•
Increased capillarization allows for:
1. a greater surface area and reduced distance
between the blood and the surrounding tissues
2. increasing diffusion capacity of oxygen and
carbon dioxide
3. easing transport of nutrients to cells.
Exercise Effects on the Cardiovascular
and Respiratory Systems cont.
• The a-vO2 difference of the body can be also
improved by endurance training.
• Endurance training increases circulation
(blood flow) in the capillaries that are next to
muscle fibers.
• Capillarization also occurs in cardiac muscle,
reducing the possibility of cardiac disease and
heart attacks.
Exercise Effects on the Cardiovascular
and Respiratory Systems cont.
Blood Volume
• Increase in total blood volume
along with the number and total
volume of red blood cells.

This is done through stimulation of
erythropoiesis (formation of new
red blood cells) in the bone
marrow.
Exercise Effects on the Cardiovascular
and Respiratory Systems cont.
Ventilation
• increases with exercise in order to meet the increased
demand of gas exchange.
• During exercise ventilation can increase from 6 L / min at rest
to over 150 L/min during maximal exercise and to more than
200 L/min during maximal voluntary breathing
• With exercise/endurance training, the lungs become more
efficient in gas exchange.
Exercise Effects on the Cardiovascular
and Respiratory Systems cont.
Oxygen Extraction
• similar to ventilation in that the increased air
flow allows for more gas exchange.
• Additionally, during exercise, body
temperature increases. Increased body
temperature promotes oxygen extraction,
this is known as the Bohr effect.
Exercise Effects on the Cardiovascular
and Respiratory Systems cont.
Summary
• Endurance training stimulates many
positive adaptations in the
cardiovascular system.
• It is crucial that the health professional
understand these adaptations in order to
impart this knowledge to the general
population allowing people to live with
greater health and a better quality of life.
Cardiovascular Anatomy and
Physiology
Discussion Questions
1.
2.
3.
4.
Describe the path and all related steps that a molecule of
oxygen would take from the air in the lungs to a muscle cell.
Describe the path and all related steps that a molecule of
carbon dioxide could take from a muscle cell to the air in the
lungs.
Define and provide the units for blood pressure, heart rate,
cardiac output, stroke volume, ateriovenous oxygen difference.
List the ways in which training improves the effectiveness of
the cardiovascular system.
Cardiovascular Anatomy and
Physiology
Discussion Questions cont.
5.
Describe the two components of blood pressure. What
do they measure?
6. What is hemoglobin, where is it found, what is its
purpose.
7. What are erythrocytes and reticulocytes? Where are
they produced?
8. What is hematocrit?
9. Describe the ways in which carbon dioxide can be
transported through the blood.
10. What is VO2max? What factors influence this measure?
How is it affected by training?