Positive feedback — Science definition
A loop in which the response amplifies the change, driving a process to completion before it shuts off.
Where it is taught
- Homeostasis & Feedback — Body Systems, Signals & Homeostasis, Life Science: Biology, Grade 10
In use
Less common, but important, is positive feedback, in which the response amplifies the change instead of reversing it, driving a process quickly to completion.
Homeostasis & Feedback
Questions using positive feedback
Problem 1
- Shivering to warm up when cold
- Insulin lowering blood sugar after a meal
- Contractions during childbirth strengthening until the baby is born
- Sweating to cool down when overheated
Answer and explanation
Contractions during childbirth strengthening until the baby is born
Childbirth contractions amplify themselves (positive feedback); sweating, shivering, and insulin all reverse a change (negative feedback).
Problem 2
Answer and explanation
Positive feedback amplifies a change, which suits processes that need to run rapidly to a definite completion: contractions intensify until delivery ends the loop, and clotting accelerates until the vessel is sealed. Each has a built-in endpoint. Temperature has no such endpoint, so amplification would drive the deviation further in the direction it had already moved, pushing the body away from the range in which its enzymes function. Regulation of a variable that must stay within a range requires a response that opposes the change.
Response criteria
- State a biologically accurate conclusion.
- Show the data, mechanism, or calculation that supports it.
- Include units, conditions, or limits where relevant.