oxytocin

Examples of oxytocin in the following topics:

• Control of Hormone Secretion

  • The hormone oxytocin is produced by the posterior pituitary that stimulates and enhances contractions during labor.
  • During birth, as the baby moves through the birth canal, pressure receptors within the cervix signal the hypothalamus to stimulate the pituitary to secrete oxytocin.
  • Oxytocin travels to the uterus through the bloodstream, stimulating the muscles in the uterine wall to contract which in turn increases the activation of the pressure receptors and stimulates further release of oxytocin.
  • The strength of muscle contractions intensifies until the baby is born and the stimulation of the pressure receptors is removed, which stops the release of oxytocin.

• The Posterior Pituitary

  • The posterior pituitary secretes two important endocrine hormones—oxytocin and antidiuretic hormone.
  • The pars nervosa, also called the neural lobe or posterior lobe, constitutes the majority of the posterior pituitary and is the storage site of oxytocin and vasopressin.
  • Oxytocin, most of which is released from the paraventricular nucleus in the hypothalamus.
  • Oxytocin is one of the few hormones that create a positive feedback loop.

• Oxytocin and Childbirth

  • When the contractions of labor begin, the walls of the uterus start to contract by release of the hormone oxytocin.
  • This process is stimulated by the release of the pituitary hormone oxytocin.
  • Oxytocin continues to be released to shrink the size of the uterus and aid in the limiting of blood loss from the site of the placenta.
  • Outline the phases of childbirth and the role played by oxytocin in them

• Overview of the Pituitary Gland

  • The posterior pituitary does not produce any hormones of its own, rather, it stores and secretes two hormones made in the hypothalamus—oxytocin and anti-diuretic hormone.

• Mammary Glands

  • The myoepithelial cells can contract under the stimulation of oxytocin thereby excreting milk secreted from alveolar units into the lobule lumen toward the nipple where it collects in sinuses of the ducts.
  • As the infant begins to suck, the hormonally (oxytocin) mediated "let down reflex" ensues, and the mother's milk is secreted into the baby's mouth.
  • Suckling of the baby causes release of hormone oxytocin which stimulates contraction of the myoepithelial cells.

• Developmental Changes in Fluids

  • The hypothalamic-neurohypophysial system plays a fundamental role in the maintenance of body fluid homeostasis by secreting arginine vasopressin (AVP) and oxytocin (OT) in response to a variety of signals, including osmotic and non-osmotic stimuli.

• Onset of Labor

  • When the contractions of labor begin, the walls of the uterus start to contract through stimulation by the release of the pituitary hormone oxytocin.

• Circumventricular Organs

  • Posterior pituitary: Stores and releases oxytocin and vasopressin, also known as antidiuretic hormone, produced in the hypothalamus.

• Dystocia and Cesarean Section

  • Oxytocin is commonly used to treat incoordinate uterine activity, but pregnancies complicated by dystocia often end with assisted deliveries, including forceps, ventouse (vacuum-assisted delivery) or, commonly, caesarean section.

• Physiology of Lactation

  • This stage requires prolactin and oxytocin.