This is an introductory activity to introduce students to the phenomenon of homeostasis. Students gather data on set point or resting heart rate, exercise, collect data again, and then relate the data to negative feedback mechanisms. Students visualize and explain homeostasis through graphing and graph interpretation. Minimal equipment is needed.
HS-LS1-3. Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.
Make certain students are healthy enough to run in place for 2 minutes prior to beginning the activity. Use this activity only in accordance with established laboratory safety practices, including appropriate personal protective equipment (PPE) such as gloves, chemical splash goggles, and lab coats or aprons. Ensure that students understand and adhere to these practices. Students should not eat, drink, or chew gum in the lab and should wash their hands after entering and before exiting the lab.
There is no chemical disposal.
Student answers will vary slightly but should be within normal range (60 to 100 beats/minute or 15 to 25 beats/15 seconds).
Resting Heart Rate
Post Exercise Heart Rate
Compare the set point heart rate for each group member
If students are healthy, the range of set point heart rates should not vary widely and will probably be within normal ranges. Students may notice slight differences between genders or athletes and nonathletes.
On the same axes, graph every group member’s average set point heart rate and post- exercise heart rates. Color code or label each line. On the graph, identify the set point, where exercise is taking place, and where corrective mechanisms are activated. Remember to title the graph, label the axes, include units, and include a key.
Using the concepts of homeostasis and negative feedback mechanisms, explain each segment of the graph.
Segment 1: The slope of the line segment is positive indicating an increase in heart rate. Exercise with an increased need for oxygen to the muscles, is the stimulus to which the circulatory must respond to maintain homeostasis.Segment 2: The slope of the line segment is negative indicating the circulatory system is in a self-correcting, negative feedback mechanism. Heart rate is coming down, returning the body to normal through the process of homeostasis.Segment 3: The slope of segment 3 is negative and very small indicating that the body is returning to set point heart rate and homeostasis is maintained.
If you collected data for a positive feedback mechanism, how would the graph change?
Segment 1: The slope of the line segment would be negative indicating a decrease in rate or amount. Segment 2: The slope of the line segment would be positive indicating a self-correcting, positive feedback mechanism. Segment 3: The slope of segment 3 would be positive and very small indicating that the body is returning to set point rate or amount and homeostasis is maintained.
Convert your heart rates to beats/min. Compare your heart rate to the normal range of 60-100 beats/min.
Energy flow was from the environment to the system. I know this because the temperature went down.
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