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).