Parturition
Initial event is increase in estradiol and oxytocin in mother’s blood.High levels of estradiol stimulate the production of oxytocin receptors in uterine smooth muscle whichincreases sensitivity to oxytocin.Oxytocin from the posterior pituitary stimulates smooth muscle contraction in the uterus.Pressure of the fetus’ head stretches smooth muscle Triggers more oxytocin release Positive feedback cycle