6 POSITIVE FEEDBACK NEGATIVE FEEDBACK Stimulatory Inhibitory Positive GnRHNegativefeedbackGnRH223(LH)3AnteriorpituitaryLH1Anteriorpituitary1EstrogenProgesterone4OvaryOvaryBefore ovulationAfter ovulation1. During the menstrual cycle, before ovulation, small amounts of estrogen are secreted from the ovary.2. Estrogen stimulates the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus and luteinizing hormone (LH) from the anterior pituitary.3. GnRH also stimulates the release of LH from the anterior pituitary.4. LH causes the release of additional estrogen from the ovary. The GnRH and LH levels in the blood increase because of this positive-feedback effect.1. During the menstrual cycle, after ovulation, the ovary begins to secrete progesterone in response to LH.2. Progesterone inhibits the release of GnRH from the hypothalamus and LH from the anterior pituitary.3. Decreased GnRH release from the hypothalamus reduces LH secretion from the anterior pituitary. GnRH and LH levels in the blood decrease because of this negative-feedback effect.
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