homeostasis

Analysis and discussion questions develop student understanding of negative and positive feedback and homeostasis.

For example, students develop a model of negative feedback regulation of body temperature; this model includes a temperature control center in the brain that uses information about differences between a setpoint and actual body temperature to regulate sweating, shivering, and changes in blood flow to the skin.

The setpoint for negative feedback can be changed; for example, in response to an infection the temperature setpoint can be increased, resulting in a fever.

Negative feedback contributes to homeostasis.

Sometimes negative feedback does not function properly; for example, diabetes results from abnormalities in negative feedback regulation of blood glucose levels.

Finally, students analyze how positive feedback contributes to rapid change (e.g., rapid formation of a platelet plug).

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. To understand changes in breathing when running, students analyze cellular respiration.

Next, students use a negative feedback model to understand temperature regulation and homeostasis. Then, students analyze how failures of negative feedback can result in diabetes. Finally, students compare and contrast positive and negative feedback.

The 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