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

• The central component primarily concerns the effectiveness of the heart and the peripheral factors include;

1. the ability of the lungs to oxygenate the blood2. 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.

VO2max = Cardiac Output x (a-vO2) difference

• 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.

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.

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. Describe the path and all related steps that a molecule of oxygen would take from the air in the lungs to a muscle cell.

2. 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.

3. Define and provide the units for blood pressure, heart rate, cardiac output, stroke volume, ateriovenous oxygen difference.

4. List the ways in which training improves the effectiveness of the cardiovascular system.

Cardiovascular Anatomy and Physiology

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?

Discussion Questions cont.