Feedback at Higher Level: An AHL statement: how signalling pathways are kept in check, or pushed to a peak.
Practise this as you read
- Distinguish negative from positive feedback.
- Identify an example of each.
Free preview
This is the free notes preview
You're reading the free notes. Aimnova Pro unlocks the full study experience — and you can try it with your first topic free to keep:
- FlashcardsLock in vocabulary and key terms with spaced repetition.
- Practice questionsAnswer exam-style questions and get instant AI marking.
- Mock exams & past-paper vaultSit full mocks and see exactly how examiners award marks.
- Personalised study planA daily plan built around your exam date and weak areas.
The big idea: The response of a signalling pathway can act back on the signal. In negative feedback the response reduces the signal, so the output stays near a set point. In positive feedback the response increases the signal, so a change grows until something ends it.
The points to remember
- Negative feedback: the response reduces the signal.
- It keeps the output stable, near a set point.
- Positive feedback: the response increases the signal.
- It amplifies a change, which grows quickly.
- Positive feedback must be ended by something else (an event, or the signal running out).
Remember it as: Negative steadies, positive snowballs.
Real examples. Negative: as insulin lowers blood glucose, the pancreas releases less insulin. Positive: before ovulation, rising oestradiol makes the pituitary release more LH, which makes the follicle release more oestradiol; the LH surge then triggers ovulation.
Trap: Negative feedback does not mean the response is bad or stops at once: it means the response opposes the change that caused it.
Learn what examiners really want
See exactly what to write to score full marks. Our AI shows you model answers and the key phrases examiners look for.
How it is asked: Expect an MCQ asking which example is positive or negative feedback, a Distinguish question, or a Predict question on what happens if feedback is blocked.
Distinguish between negative and positive feedback in the regulation of a signalling pathway.
Model answer plan
See the answer broken into clear points, with guidance on how each point earns marks.