= Oxytocin
<Oxytocin> is a nine-<amino acid> <peptide hormone> synthesized by <neurons> in the <hypothalamus> and released into the circulation from the <posterior pituitary>. It promotes contraction of uterine <smooth muscle> during childbirth and contraction of cells around mammary secretory units, ejecting milk. Milk ejection is distinct from producing the milk.<Anatomy and Physiology 2e by J. Gordon Betts and others>[Section 17.3, Oxytocin]{ref}
Childbirth illustrates <positive feedback>: stretching of the cervix stimulates a neural pathway that increases <oxytocin> release; stronger uterine contractions can increase the stretch until delivery removes the initiating stimulus. During suckling, sensory input similarly couples an external event to <hormone> release and milk ejection. These circuits connect <sensory neurons>, endocrine signaling and mechanical action.<Anatomy and Physiology 2e by J. Gordon Betts and others>[Section 17.3, Oxytocin, childbirth and milk-letdown feedback]{ref}
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