Positive Feedback

Positive feedback systems are rare. They occur when secretion of a hormone increases in response to feedback from an organ, creating an amplification process.

Example

The hormone Oxytocin causes uterine contraction. During parturition, the uterus stretches. The stretch causes nerve impulses to send signals to the hypothalamus, increasing the oxytocin levels released. This in turn increases uterine contraction, and the cycle continues.