Negative feedback happens the
response to given action generates
effect that inhibits action. For
example, the carbon dioxide
in blood is the
pulmonary respiration stimulated for
the excess to be through
expiration. Hyperventilation, ,
lowers the carbon concentration
in blood much generating a
feedback that commands reduction
of the frequency.

Negative feedback the main
mechanism homeostasis and it
in a variety processes, such as
blood pressure control, ,
muscle contraction, etc.