Discussion

Each cell in the muscles needed more oxygen when doing more work because of increased cellular respiration within the cell.
Each cell also required glucose, which is part of cellular respiration.
Two substances produced during cellular respiration are carbon dioxide and water.

Cellular Respiration Formula:

Cell food + Oxygen = Energy + CO2

C6H12O6 + O2 = CO2 + H2O + Energy
(Glucose + Oxygen) = (Carbon Dioxide + Water + Energy)
(Fuel)

Blood is the transport system for oxygen, glucose, carbon dioxide and part of the water. Blood is made up of red blood cells, white blood cell, platelets and plasma.

Oxygen in the blood is carried by a system of tubules made-up of arteries, arterioles, and capillaries. Oxygen diffuses from the high concentration in the arterial capillaries into the area of low concentration in the cell. Oxygen attaches itself to the erythrocytes that are red blood cells. Erythrocytes contain hemoglobin, which is a molecule that contains an iron atom. Oxygen binds itself to that iron atom.

Carbon dioxide diffuses from the high concentration in the cells into the area of low concentration in capillaries around the cell.
The capillaries carry the blood rich in carbon dioxide to the venues and then to the veins. The veins carry the carbon dioxide to the upper and lower vena cava that lead into the right atrium. The carbon dioxide then goes through the heart where it is pumped via the pulmonary artery into the lungs so that it can become rich in oxygen.

Receptors, such as the one in the aorta, detect the rise in carbon
Dioxide in the body as the blood leaves the left ventricle. The
Carbon dioxide receptor examines the level of carbon dioxide in the blood. The receptor sends a signal to respiratory centre in response to an increase or decrease in the levels of carbon dioxide. The respiratory centre is located in the medulla oblongata at the base of the brain.

The respiratory centre, which is part of the central nervous system and part of the autonomous nervous system, sends a signal to the muscles involved with respiration such as the intercostals muscles in the rib cage and the diaphragm to work faster if the levels of carbon dioxide have increased. These signals occur very quickly. During the intense activity level the abdominal muscles were also activated by the respiratory system. This was not part of the procedures so in the next repetition of the experiment this should be included in the procedures as one of the variables to observe.

As the muscles around the lungs contract, they enlarge the area around the lungs. The enlarged area around the lungs decreases the pressure in the lungs. The pressure outside the body is greater at that point than in the lungs so air from the outside is forced into the lungs by the difference in pressure. As the muscles relax and return to their original positions, the higher pressure on the lungs forces air from the lungs into the air.

The lungs are comprised of two main sections, which are the left and the right lungs. Air from the outside enters through the nasal cavity and/or the mouth and descends down your windpipe and then into your lungs. The air then goes through many bronchial tubes and then it finally reaches your air sacs (alveoli). “Through very thin walls of the alveoli, oxygen from the air passes to the surrounding capillaries (blood vessels). A red blood cell protein called hemoglobin (HEE-muh-glow-bin) helps move oxygen from the air sacs to the blood. (Oxygen is especially drawn to hemoglobin.)”

The results in the experiment indicate that both respiration and pulse increased with higher activity levels. The mean results support the hypothesis. The range in the results can be explained by different levels of strenuous activities, some requiring more oxygen, and by different levels of fitness among the subjects.

It would be worthwhile to add a further dimension to the experiment by analyzing how long it takes the body to resume the normal pulse and respiration to determine when oxygen levels returned back to normal. The hypothesis would be the faster that the subject's pulse and respiration returned to normal, the better is the subject's cardiovascular and pulmonary systems. Another addition to the experiment would be to have some subjects inhale oxygen. The hypothesis would be that the subjects inhaling oxygen would return to their normal pulse and respiration rates faster than subjects who were not provided with oxygen.

The experiment could also test the level of carbon dioxide produced at the different levels of activity. This can be measured by having the subject’s blow through a straw into limewater. Limewater turns murky white in the presence of carbon dioxide as done in a previous experiment this year. The faster the limewater turned milky white, the more carbon dioxide the subject must be exhaling.