An example of homeostatic control through positive feedback in HUMAN SYSTEMS ?

A nerve impulse (action potential) in a nerve builds to its peak through positive feedback--the opening of sodium channels causes in influx of sodium which causes the inside of the cell just under the membrane to become less negative, this causes more sodium channels to open, more sodium enters, the inside becomes even more less negative, that causes more channels to open, etc......An example of homeostatic control through positive feedback in HUMAN SYSTEMS ?
Positive feedback amplifies changes made by a stimulus, in other words, it maximizes the effect of a stimulus. An example of positive feedback would be childbirth, where contractions (through the use of the hormone oxytocin) are intensified until the child is out.

smokey eye