What is the difference between positive and negative feedback mechanisms?

Positive feedback mechanisms amplify a change, while negative feedback mechanisms counteract a change.

Positive feedback mechanisms are those that amplify or reinforce a change in the body. They work by increasing the initial stimulus, leading to a greater response. This can be seen in processes such as blood clotting, where the formation of a clot triggers the release of more clotting factors, leading to the formation of a larger clot. Another example is the release of oxytocin during childbirth, where the initial contractions of the uterus stimulate the release of more oxytocin, leading to stronger contractions and the eventual delivery of the baby. For a detailed look at how hormones like oxytocin function, see our notes on hormonal control.

On the other hand, negative feedback mechanisms work to counteract or reduce a change in the body. They work by detecting a change and activating a response that opposes the change, thereby maintaining a stable internal environment. This can be seen in processes such as temperature regulation, where an increase in body temperature triggers a response to cool the body down, and a decrease in body temperature triggers a response to warm the body up. Another example is the regulation of blood glucose levels, where an increase in blood glucose triggers the release of insulin, which lowers blood glucose levels, and a decrease in blood glucose triggers the release of glucagon, which raises blood glucose levels. To understand how these mechanisms contribute to maintaining homeostasis, refer to our definition of homeostasis.

Additionally, the processes of mitosis and meiosis are tightly regulated by feedback mechanisms to ensure proper cell division and genetic stability.

A-Level Biology Tutor Summary: Positive feedback mechanisms amplify changes, like making blood clots bigger or increasing contractions during childbirth. Negative feedback mechanisms balance changes, like regulating body temperature or blood glucose levels. Essentially, positive feedback adds more to a process, and negative feedback adjusts to keep things stable, ensuring our body's systems work correctly and stay in balance.