Cambridge O Level Biology · Syllabus 5090 · Coordination and Control
Negative Feedback
What is Negative Feedback?
A control mechanism in which a change in a variable produces a response that opposes that change, returning the variable towards its set point. As the variable returns, the corrective response is reduced. The word negative refers to opposing the deviation, not to any harmful effect.
This definition is part of the Coordination and Control chapter in Cambridge O Level Biology.
Negative Feedback in context
Coordination is how an organism detects a change and produces a useful response to it. Every example in this chapter — pulling a hand off a hot pan, narrowing a pupil, sweating on a hot afternoon, storing glucose after a meal — runs through the same five stages: stimulus → receptor → coordinator → effector → response. Mammals run that chain two ways. Nervous control sends electrical impulses along neurones: fast, precisely targeted, usually short-lived. Hormonal control sends chemicals dissolved in blood plasma: generally slower, more widespread, often longer-lasting. Homeostasis is the job both systems do together — holding internal conditions within narrow limits by negative feedback, in which every correction opposes the change that triggered it.
Common mistakes with Negative Feedback
- Do not let the temperature fall for ever. These responses do not run until the body is cold. As the temperature returns towards the set point, the deviation being detected gets smaller and the corrective response is reduced — sweating slows, the arterioles return towards their normal diameter. That is negative feedback, and mentioning it turns a good answer into a complete one.
Questions students ask about Negative Feedback
What is negative feedback?
Negative feedback is a control mechanism in which a change in a variable produces a response that opposes that change, returning the variable towards its set point. As the variable returns, the corrective response is reduced. "Negative" means opposing the deviation; it does not mean harmful.