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Negative Feedback, Homeostasis, and Positive Feedback, with Breathing Experiment
This minds-on, hands-on activity begins with an anchoring phenomenon, how a person’s breathing changes when he/she is re-breathing the air in a plastic bag. Students develop a negative feedback model of how the changes in breathing stabilize blood levels of O2 and CO2.
Then, students use a negative feedback model to understand temperature regulation, homeostasis, and how a change in setpoint can result in a fever.
Next, students analyze how failures of negative feedback regulation of blood glucose levels can result in diabetes.
Finally, students compare and contrast positive and negative feedback. Throughout this activity, students learn relevant human physiology.
An Appendix for the Teacher Preparation Notes suggests an optional activity in which each student group investigates a question or hypothesis concerning negative feedback, homeostasis and changes in breathing.
Download Student Handout: PDF format or Word format
Download Teacher Preparation Notes: PDF format or Word format
The Teacher Preparation Notes provide instructional suggestions and background information and explain how the activity is aligned with the Next Generation Science Standards.
We invite comments on this Hands-On Activity and the accompanying Teacher Preparation Notes, including suggestions for other teachers who are planning to use the activity, any questions you have related to the activity, or a brief description of any problem you might have encountered. If you would prefer to send your comments or questions in a private message, please write Ingrid Waldron at iwaldron@sas.upenn.edu.
Comments
2023 revision
We have reorganized the Student Handout to begin with the phenomenon of deeper and faster breathing as students re-breathe the air in a plastic bag and then explore an explanation for this and related phenomena. We have also added a section on diabetes which will help the students appreciate the practical significance of understanding negative feedback. We have also revised multiple explanations and questions to improve the clarity of the Student Handout. To accommodate these revisions, we have totally revised the Teacher Preparation Notes.
Ingrid
2019 revision
I have reorganized the sections of the Student Handout on negative feedback and changes in breathing to begin with an anchor phenomenon and have students work to figure out an explanation of this anchor phenomenon. I have also streamlined the Student Handout and made multiple revisions to improve clarity.
Ingrid
2018 revision
The Student Handout has been substantially revised to clarify the concepts and improve student understanding.
Video which Demonstrates Experimental Technique
We have prepared a video to demonstrate the procedure for the first experiment and help your students get more reliable results. The video available at https://www.youtube.com/watch?v=l60LE0M0bk8&feature=youtu.be demonstrates how to prepare the bag and breathe into the bag. You will want to view this video and then either demonstrate the procedure for your students or have them watch this video. Helpful advice includes:
November 2015 revision
This revision includes improved instructions for the experimental methods, some clarification of explanations and questions, and additional biological information which will help with the interpretation of the experimental results.
2015 Revision
This 2015 activity, "Homeostasis and Negative Feedback – Concepts and Breathing Experiments", is essentially a new activity with a minor overlap with the previous breathing activity. This 2015 activity includes:
This activity is aligned with the Next Generation Science Standards (see page 1 of the Teacher Preparation Notes).
filling the 13 gallon bag results/data interpretation
Could you explain what results should come from this part of the lab exercise?
I would predict a shorter time than after normal breathing but why?
regulation of breathing
As indicated by the questions on the top part of page 5 of the Student Handout, breathing into the bag results in increased concentration of CO2 in the bag and decreased concentration of O2. This in turn results in increased concentrations of CO2 and decreased concentration of O2 in the blood and in the brain. The length of time you can hold your breath decreases as a result of these changes. If you carry out the Additional Activity described on page 2 of the Teacher Preparation Notes, the results will demonstrate that the brain is responding specifically to changes in CO2 levels, not O2 levels. In fact, it is the increased concentration of H+ (which is generated when CO2 combines with H2O in the blood to form carbonic acid) which stimulates the brain to resume or increase breathing.
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