The human cardiovascular system consists of the heart, the blood, and a system of transporting vessels. A human heart has four chambers: a right and left atrium and a right and left ventricle. The fist-sized heart sits in its own sac (the pericardium) in the middle of the chest under the sternum. In most people, the apex of the heart points to the left. There are two circuits of simultaneous blood flow in humans: a pulmonary circuit and a systemic circuit. In the pulmonary circuit, the right ventricle pumps deoxygenated blood to the lungs for gas exchange. At the same time, oxygenated blood that has come from the lungs to the left side of the heart is pumped to the body’s cells (the systemic circuit) for gas exchange. The deoxygenated blood is returned to the right side of the heart. Strenuous exercise causes a dramatic increase in blood flow to skeletal muscles that depend on the red blood cells to bring them the oxygen necessary for cellular respiration , which is the quantity of blood pumped from one’s heart and clinically measured per minute. There are several points in the body where the heart rate may be taken, but it is read clinically at the wrist over the radial artery. Cardiac output is important because it determines one’s potentials for gas exchange and thus physical activities. Exercise over time increases one’s physical fitness. A way to measure fitness is by taking a blood pressure reading. Blood pressure is read by a device called a sphygmomanometer. Blood pressure is the force of blood moving along the elastic walls of arteries. The top number is the systolic reading, corresponding to the contraction phase of the heartbeat. The bottom number is the diastolic reading and corresponds to the relaxation phase of the heartbeat. A healthy at-rest systolic reading for a young adult would be 110 to 120 mmHg (millimeters of mercury). A good at-rest diastolic reading would be 70 to 80 mmHg. It is measured clinically over the brachial artery using a blood pressure cuff.
The premise behind this experiment is that as time elapses after exercise, the metabolic demands on our cardiac output will also lower. This is a direct relationship. Checking the heart rate after exercise is a way to gauge the demand for oxygen to our cells. The scientific method has no rigid format, but it has several vital components. The observation of a phenomenon leads to a question which must be as free of preconceived bias as possible. This leads to the formation of a hypothesis, which is a tentative explanation for the possible cause of the observed phenomenon. The hypothesis is preferably worded as a prediction in an if-then format. Observation, study, and knowledge all contribute to the construction of the hypothesis. You also write a null hypothesis. This is a negative restatement of the hypothesis. We then develop an experiment which should yield data that either supports or refutes the hypothesis. There are certain variables or factors to consider in constructing the experiment. The independent (x) variable is the variable which the experimenter manipulates. In this case, it is the time elapsed after exercise. Minutes elapsed represents levels of treatment. The dependent (y) variable) is the responding variable. In this case, respirations per minute comprises the y variable. Controlled variables are independent variables which must be kept constant in order to determine the effects of the independent variable being manipulated on the dependent variable. Therefore, distracting the participants in any way should be avoided and the timing of the treatments should be adhered to as closely as possible. Experimental error consists of intrinsic factors which may affect results of any experiment. They are always present. These are the variables which the experimenter cannot fully control or may even be unable to identify. This inevitable level of uncertainty bars proving anything in science. A separate...
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