Link progesterone and oestradiol to pregnancy maintenance, then trace oxytocin positive feedback during childbirth in IB Biology HL D3.1.19.
Feedback mechanisms are used in living organisms both to promote and respond to change.
Describe the hormone feedback mechanisms that help to prepare a woman's body for pregnancy, sustain the pregnancy and then give birth.
Preparing the woman's body for pregnancy:
FSH stimulates estrogen secretion by the developing follicle.
Estrogen increases FSH receptors, boosting estrogen production/causing positive feedback.
Estrogen stimulates repair/thickening of the endometrium/uterus lining.
High levels of estrogen stimulate LH production/inhibit FSH secretion (negative feedback).
LH surge/peak stimulates ovulation.
Sustaining pregnancy:
LH stimulates development of the corpus luteum / corpus luteum secretes progesterone.
Progesterone inhibits FSH/LH secretion (negative feedback).
Progesterone maintains the lining of the uterus/endometrium for pregnancy/implantation of the embryo.
Progesterone inhibits uterine contractions.
HCG secreted by the embryo stimulates maintenance of the corpus luteum.
Childbirth:
Oxytocin stimulates uterine/myometrial contractions which stimulate oxytocin secretion.
Positive feedback mechanism is used to stimulate childbirth.