28. While the initial release of oxytocin, the hormone that triggers the onset of childbirth, is not fully understood, scientists do know that high levels of the hormone estrogen lead to the formation...

Extracted text: 28. While the initial release of oxytocin, the hormone that triggers the onset of childbirth, is not fully understood, scientists do know that high levels of the hormone estrogen lead to the formation of receptors for the oxytocin on the uterus late in pregnancy. Oxytocin causes the uterus to contract, and uterine contractions stimulate the pituitary gland to release more oxytocin. Which statement best explains how the uterus and the pituitary gland work together during childbirth? a. Uterine contractions signal the pituitary gland to release more oxytocin via a negative feedback loop, which causes the frequency and intensity of uterine contractions to be maintained at a constant rate until birth occurs. b. Uterine contractions cause the pituitary gland to release oxytocin via a negative feedback loop, which increases the frequency and intensity of uterine contractions until birth occurs. c. Oxytocin causes uterine contractions, which cause the pituitary gland to secrete more oxytocin and cause more uterine contractions via a positive feedback loop, which increases the frequency and intensity of the contractions until birth occurs. d. Oxytocin is released only in response to uterine contractions via a positive feedback loop, which causes the frequency and intensity of uterine contractions to be consistent until birth occurs.