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Negative Feedback, Homeostasis, and Positive Feedback

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).

How do muscles get the energy they need for athletic activity?

ATP in muscle cells

In this analysis and discussion activity, students learn how muscle cells produce ATP by aerobic cellular respiration, anaerobic fermentation, and hydrolysis of creatine phosphate. They analyze the varying contributions of these three processes to ATP production during athletic activities of varying intensity and duration.

Students learn how multiple body systems work together to supply the oxygen and glucose needed for aerobic cellular respiration.

Finally, students use what they have learned to analyze how athletic performance is improved by the body changes that result from regular aerobic exercise.

Structure and Function of Cells, Organs and Organ Systems

Process of phagocytosis after injury to skinIn this activity, students analyze multiple examples of the relationship between structure and function in diverse human cells and in the digestive system.

Students learn that cells are dynamic, with constant molecular activity.

Students analyze examples that illustrate how organelles work together to accomplish cellular functions and organs and organ systems work together to accomplish functions needed by the organism.

Finally, students evaluate the claim that structure is related to function in cells, organs and organ systems.

How do we sense the flavors of food?

Olfactory receptors and olfactory bulb sending messages to other parts of brainIn this minds-on, hands-on activity, students develop science practice skills by developing plans for a hands-on investigation, carrying out the investigation, analyzing the data, and interpreting the results.

Then, students answer analysis and discussion questions as they develop a basic understanding of how taste and olfactory receptor cells function and how sensory messages to the brain contribute to flavor perception and flavor-related behavior.

Negative Feedback, Homeostasis, and Positive Feedback – Examples and Concepts

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

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