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 (C6H12O6 + 6O2 ‡ 6CO2 + H2O + Energy).

Blood is the transport system for oxygen, glucose, carbon dioxide and part of the water. Blood is made up of plasma, red blood cells, white blood cells and platelets. Platelets are mainly water, but also contain sugars, slats, CO2, proteins and hormones. 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 venules 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 blood then flows into the right ventricle which is the lower chamber on the right side of the heart. The blood is then forced through the pulmonary valve into the pulmonary artery which leads to both the lungs to pick up oxygen and release carbon dioxide. 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 center 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 intercostal 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. The left and the right lungs. Air from the outside enters through the mouth and nose and passes through the larynx and the trachea (the tube that enters the chest area). In the chest area, the trachea splits into two smaller tubes called the bronchi. The bronchus then divides again and becomes the bronchial tubes. The bronchial tubes lead to the lungs where they divide into smaller tubes that connect to tiny sacs called alveoli. The Alveoli store air for a brief period of time to allow the oxygen to be absorbed into the blood-stream.

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 subjects blow through a straw into lime water. Lime water turns murky white in the presence of carbon dioxide as done in a previous experiment this year. The faster the lime water turned milky white, the more carbon dioxide the subject must be exhaling.