Negative and positive feedback

Respiration, Muscles and the Internal Environment · Homeostasis, hormones and the kidney · note 1 of 7

Spec 7.16

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Negative and positive feedbackSpec 7.16

In short

Negative feedback is a control mechanism in which a change in a factor is detected and corrected, returning it towards its set point, so the factor stays within narrow limits. In positive feedback, a change leads to responses that increase the change further, moving the system away from its starting point.

Most control systems in the body contain the same components: a receptor detects a change in a factor, a coordination centre (for example the hypothalamus) processes the information, and an effector (a muscle or gland) brings about a response.

Negative feedback

In negative feedback, the response reverses the original change. If the factor rises above the set point, the response makes it fall; if it falls below, the response makes it rise. The factor therefore fluctuates around the set point within narrow limits. Having receptors and effectors that work in opposite directions (for example vasoconstriction and vasodilation) gives control in both directions.

A factor changes from its set point (the stimulus).
Receptors detect the change and send information to the coordination centre.
The coordination centre sends signals (nerve impulses or hormones) to effectors.
Effectors produce a response that reverses the change.
The factor returns to its set point and the stimulus is removed, so the response is switched off.

Positive feedback

In positive feedback, the response increases the change away from the set point. It is not used to maintain a steady state. It is useful when a rapid, complete change is needed, for example the stimulation of uterine contractions by oxytocin during birth, and the opening of voltage-gated sodium channels in an action potential. If it is not stopped it can be harmful.

Common mistake:

'Negative' does not mean the effect is bad or that the response decreases the factor. Negative feedback reverses whichever change occurred. Positive feedback amplifies it.

A negative feedback loop (change, receptor, coordination centre, effector, response reversing the change) with a graph oscillating about the set point, beside a positive feedback loop where the response increases the change and the factor moves further from the set point. — Negative feedback reverses a change; positive feedback amplifies it.

Written and checked against the Edexcel International A Level Biology (YBI11) specification · Updated October 2026

Frequently asked questions

What is the difference between negative and positive feedback?

In negative feedback the response reverses the change, so a factor such as temperature stays near its set point. In positive feedback the response increases the change and moves the factor further away, as with oxytocin in childbirth. Homeostasis relies on negative feedback.

How does the body regulate temperature during exercise?

Respiration in muscles releases heat, raising the temperature of the blood. Thermoreceptors in the hypothalamus detect this and trigger vasodilation of skin arterioles and sweating. These transfer heat to the surroundings, so core temperature returns to the set point by negative feedback.

How does the kidney filter blood in ultrafiltration?

The afferent arteriole is wider than the efferent arteriole, so blood in the glomerulus is at high pressure. Water and small solutes are forced through pores in the capillary endothelium, the basement membrane and the podocytes into the Bowman's capsule, while blood cells and large proteins stay in the blood.

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