# Positive Feedback Loop

## Introduction

Feedback is a property of a system to take its own outputs as part of its inputs, and thus a loop is formed. This empowers an organism to regulate its biochemical environment and allows it to express product (e.g. proteins) differenly upon changes.

A positive feedback loop (PFL) further limits to the situation that a deviation of the controlled quantities (i.e. its outputs as well as its inputs) are in turn amplified by the system. On the other hand, negative feedback loop(NFL) will counterbalance the change of controlled quantities. (Mitrophanov & Groisman, 2008)