Afferent nerve impulses from the uterus to the hypothalamus cause the release of oxytocin, a hormone of the posterior pituitary gland (contrast the mechanism of release with the hormones of the anterior pituitary gland). Oxytocin promotes contraction of uterine muscles as well as stimulates the synthesis of prostaglandins in the uterus during parturition. Through oxytocin release, uterine contractions exert a positive-feedback effect upon themselves.