Labor is an example of a positive feedback system. The uterine contractions force the cervix to stretch, which causes the hypothalamus to produce oxytocin which is released by the pituitary. The use of epidural anesthesia appears to reduce the nerve impulses sent by the cervical stretch receptors, thus reducing the secretion of oxytocin. Which explains why a very large percentage of women who receive epidural anesthesia also receive pitocin to augment their labors due to the sluggish contractions that often accompany use of epidural anesthesia.
I think you could find more information about this feedback system in an A&P text.
Michelle H. Kinne ICCE CD(DONA) CLE
www.DoulaDiva.org
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