Testable Question: Will a human’s heart and respiratory rate increase after exercise?Hypothesis: If a human exercises for two minutes then their heart rate and respiratory rate willincrease. Hypothesis Reasoning: Negative feedback loops say epinephrine will increase heart rate and that more air will get breathed in by the person. Negative feedback loops are a big part of exercising, therefore the heart and breathing rate of the person will increase. Graph: Results: This lab was conducted to see if the heart rate and respiratory rate of a human would increase after exercise. As shown by the data, after exercising the heart rate and respiratory rate increased. The percent change from pre and post exercising heart rate was 65.4% and the percent change from pre and post exercising respiratory rate was 29.7%. The average resting heart rate was 76.2 beats per minute. The average post exercise heart rate was 126 beats per minute. The average resting respiratory rate was 24.6 breaths per minute. The average post exercise respiratory rate was 31.9 breaths per minute. Unexpected heart rate data was when the heart rate was higher after exercising, such when the heart rate went from 80 beats per minute to 72 beats per minute and 64 beats per minute to 60 beats per minute. Another part of unexpected heart rate data was when the heart rate stayed the same after exercising, such as 80 bpm before exercising and 80 bpm after exercising. Unexpected data for the respiratory rate was when the respiratory rate was 28 breaths per minute before and 24 breaths per minute post exercising. There were 6 cases where the respiratory rate was 24 breaths per minute before and after exercising which are also unexpected. Explanation: The hypothesis was mostly supported by the data; however, there were a few unexpected data points where the heart rate was higher before the person exercised, or the heart rate stayed the same after exercising. The same goes for breathing where the respiratory rate was higher before the exercise or stayed the same after exercising. Most of the time the heart rate and respiratory rate increased after exercise because of the negative feedback loops trying to maintain homeostasis in the body. Homeostasis is how the body attempts to make an equal balance in itself so that the human can survive; such as the processes of cellular respiration and negative feedback loops. Cellular respiration helps maintain homeostasis by making oxygen and letting out carbon dioxide. Two negative feedback loops occur because of exercise. Negative feedback loops help maintain homeostasis. These negative feedback loops happen at the same time. The first negative feedback loop starts with exercising which increases CO2 in muscles and decreases oxygen traveling around. The CO2 is acidic and it lowers the pH of the blood. Since the pH of the blood is lowered, nerve receptors pick up on it and a message for the diaphragm and muscles to start contracting faster gets sent to the lower brain stem. After the contracting gets faster there is decreased CO2 in the blood and more CO2 is exhaled out of the body to maintain homeostasis. Then, pH levels in the blood and oxygen levels in the muscles start to rise. The second negative feedback loop is when exercise starts to make the brain get excited and the brain sends a signal to the adrenal glands to release epinephrine. The epinephrine is adrenaline and it increases the heart rate in the body which leads the person to breathe in more air and allows blood to flow faster to the muscles. More air being breathed in and blood flowing faster to the muscles is also an attempt by the body to maintain homeostasis.

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