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Describe the role of oxytocin in labor.
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Correct answer:
Oxytocin acts on receptors on myometrial cells and directly activates G proteins. Activated G proteins then activate activate phospholipase C and inositol triphosphate which cause an increase in intracellular calcium levels, a final common pathway for the induction of myometrial contractions. During the switch from contractures to contractions and recognizable labor, oxytocin concentrations increase along with the number of oxytocin receptors on the myometrium. Oxytocin also promotes prostaglandin production and gap junction formation in the uterus, augmenting its efficiency in initiating and supporting labor. During phase 2 of labor, increasing levels of oxytocin promote the increasing frequency and strength of uterine contractions and expulsion of the fetus.
