Summary
An effect amplifies its own cause, as in labour contractions and the LH surge.
In depth
Examples: oxytocin during labour, LH surge triggered by oestrogen, blood clotting cascade, and action potential upstroke. It drives processes to completion and requires a terminating event.
Positive feedback increases deviation and drives events to completion. Examples are rare in physiology. It needs a stopping mechanism.
Key idea: labour, LH surge and clotting are positive feedback examples.
In positive feedback, a change triggers responses that amplify the change, driving the system away from its starting state until an end event stops it. It is less common than negative feedback because it is unstable.
Physiological examples are the LH surge, where rising oestrogen causes more LH, leading to ovulation; childbirth contractions and oxytocin; blood clotting, where activated platelets recruit more platelets; and the rising phase of a nerve action potential, where sodium entry opens more sodium channels. Each loop ends when the event completes.
Example: a blood clot forms quickly at a wound by a cascade.
Common mistake: positive does not mean good; it means amplifying.
Frequently asked questions
What is Positive Feedback?
An effect amplifies its own cause, as in labour contractions and the LH surge.
Which area of biology covers Positive Feedback, and how advanced is it?
Positive Feedback is one of the 54 topics in Reproduction & Endocrinology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Parturition, Negative Feedback in Endocrine Control, Lactation.
Can you give an example of Positive Feedback?
Milk let-down also uses oxytocin positive feedback.
What should I learn before Positive Feedback?
Work through the Beginner topics in Reproduction & Endocrinology first, such as Reproduction, Asexual Reproduction, Sexual Reproduction, then return to Positive Feedback. Intermediate topics assume the Beginner vocabulary.
What topics are related to Positive Feedback?
The closest topics to Positive Feedback are Parturition, Negative Feedback in Endocrine Control, Lactation, Hormonal Control of the Menstrual Cycle. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Positive Feedback?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Positive Feedback. To practise the whole of Reproduction & Endocrinology, use the Reproduction & Endocrinology quiz.
How is Positive Feedback different from Parturition?
Positive Feedback: An effect amplifies its own cause, as in labour contractions and the LH surge. Parturition: Positive feedback between oxytocin and uterine contractions drives childbirth. Read both side by side and note what each one explains.
What is a common mistake about Positive Feedback?
Positive does not mean good; it means amplifying.
How should I study Positive Feedback step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Parturition and explain the difference aloud. Finally, take the Reproduction & Endocrinology quiz and come back to this page for any question you miss.