Please help me understand positive/negative feedback?

Question

how do you define them?

please help me compare and contrast their similarities/differences.

examples are appreciated

thank you

Answer 1

Negative feedback is important to maintaining homeostasis, or physiological balance.  The general idea is that as some physiological process occurs, the products of that process turn it off so that you don't make too much.  There are so many examples....the most common is that in a chain of enzymatic reactions, the final product in some way interferes or shuts down one of the enzymes in the process so that it will no longer be making the product.  

Positive feedback would encourage the process as the product occurs.  The examples are rarer since the body want to remain in balance, but the most obvious is labor where pressure of the baby in the birth canal releases oxytocin which increases contractions.