Negative feedback undoes a change. Positive adds to it.
- The idea
- Predict
- See it
- Why
- Check
The idea
“Positive feedback brings things back to normal, and negative feedback makes things worse.”
Positive sounds good and negative sounds bad, so a loop that fixes a problem seems positive. In biology the words describe what the response does to the change.
The short version
The mistake: Positive feedback brings things back to normal, and negative feedback makes things worse.
What's actually true: Negative feedback reverses a change and brings a variable back toward its set point. Positive feedback amplifies the change.
- Negative feedback opposes a change and returns the variable toward its set point, the value the body maintains. This is how homeostasis works.
- Positive feedback adds to the change, so it grows faster and faster. It stops when an outside event ends it, like a birth or a sealed wound.
On the exam: Does the response undo the change or add to it? Undo is negative. Add is positive.