A growing response isn't feedback by itself
- The idea
- Predict
- See it
- Why
- Check
The idea
“If a response keeps growing, speeding up or lasting, that's positive feedback.”
Positive feedback makes a response grow. So when one hormone ends in millions of glucose molecules, it looks like a loop.
The short version
The mistake: If a response keeps growing, speeding up or lasting, that's positive feedback.
What's actually true: A process is feedback only when its output acts back on an earlier step, however much the signal grows.
- Amplification means each step switches on many copies of the next. That's how a signaling cascade turns one hormone into a huge response.
- Feedback means an output acts on an earlier step. Positive feedback pushes that step harder. Negative feedback slows it.
- So follow the arrows from the output. If one returns to an earlier step, it's feedback.
On the exam: Feedback needs an arrow from the output back to an earlier step. Big, fast or lasting isn't enough.