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Cells use feedback loops to sustain, amplify, and inhibit the signals generated in signaling pathways.

A positive feedback loop occurs when a downstream component in a signaling pathway activates an upstream component. The loop can lead to a sustained signaling response that continues in the absence of an extracellular signal.

The sustained signals cause further activation of multiple downstream signaling components, resulting in amplification of the signal, which may increase with time.

A negative feedback loop occurs when a downstream component in a signaling pathway inhibits an upstream component resulting in dampening or stopping the response.

Since a continuous signal can be harmful to cells, the intensity and duration of a signal are controlled by negative feedback.

Positive and negative feedback can regulate distinct cell signaling pathways or be coupled together to control the same signaling pathway.