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.

• Labor and Birth

  • Toward the end of the third trimester, estrogen causes receptors on the uterine wall to develop and bind the hormone oxytocin.
  • The oxytocin causes the smooth muscle in the uterine wall to contract.
  • A positive feedback relay occurs between the uterus, hypothalamus, and the posterior pituitary to assure an adequate supply of oxytocin.
  • If labor should stop before stage two is reached, synthetic oxytocin, known as Pitocin, can be administered to restart and maintain labor.
  • Oxytocin is also released, promoting the release of the milk.

• Hormonal Regulation of the Reproductive System

  • The posterior pituitary releases the hormone oxytocin, which stimulates uterine contractions during childbirth.
  • The uterine smooth muscles are not very sensitive to oxytocin until late in pregnancy, when the number of oxytocin receptors in the uterus peaks.
  • Stretching of tissues in the uterus and cervix stimulates oxytocin release during childbirth.
  • Oxytocin also stimulates the contraction of myoepithelial cells around the milk-producing mammary glands.
  • Oxytocin release is stimulated by the suckling of an infant, which triggers the synthesis of oxytocin in the hypothalamus and its release into circulation at the posterior pituitary.

• 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

• Biological Influences on Sexual Motivation

  • Biologically, sexual motivation is influenced by hormones such as testosterone, estrogen, progesterone, oxytocin, and vasopressin.
  • The hormones oxytocin and vasopressin may also help to regulate males' sexual motivation.
  • Oxytocin is released at orgasm and promotes both emotional bonding and sexual pleasure.
  • Based on the pleasure model of sexual motivation, the increased sexual pleasure that occurs following oxytocin release may encourage motivation to engage in future sexual activities.
  • Research suggests that testosterone, oxytocin, and vasopressin are also implicated in female sexual motivation in similar ways that they are for males, but more research is needed to understand these relationships.

• Biology of Sexual Behavior

  • Oxytocin, also known as the "hormone of love," is released during sexual intercourse when an orgasm is achieved.
  • Oxytocin is also released in females when they give birth or are breast feeding; it is believed that oxytocin is involved with maintaining close relationships.
  • Both prolactic and oxytocin stimulate milk production in females.
  • Research suggests that testosterone, oxytocin, and vasopressin are also implicated in female sexual motivation in similar ways as they are in males, but more research is needed to understand these relationships.

• Lipid-Derived, Amino Acid-Derived, and Peptide Hormones

  • The peptide hormones include molecules that are short polypeptide chains, such as antidiuretic hormone and oxytocin produced in the brain and released into the blood in the posterior pituitary gland.
  • The structures of peptide hormones (a) oxytocin, (b) growth hormone, and (c) follicle-stimulating hormone are shown.

• 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.

• Control of Homeostasis

  • The hormone oxytocin, made by the endocrine system, stimulates the contraction of the uterus.
  • Instead of lowering the oxytocin and causing the pain to subside, more oxytocin is produced until the contractions are powerful enough to produce childbirth .