According to model 3. During the child birth the stimulus is baby pushes against the cervix and the response would be hypothalamus oxytocin to male uterine walls contract.
Explanation:
The first contractions of the stimulus (labor) pushes the baby towards the cervix that is the lowest part of the uterus. Normal childbirth is done by positive loop. A positive feedback loop is the change in body status than a return to homeostasis.
One of the best example for positive feedback system is child birth. During labor, a hormone called oxytocin is released which intensifies and speeds up contractions.
Child birth will eventually stop the stimulus and stop the child birth feed back loop.
