ANIMAL REPRODUCTION QUESTION 1979: L. PETERSON/AP BIOLOGY Describe the role of the hypothalamus, the pituitary hormones, and the ovarian hormones in the regulation of the human menstrual cycle. Include in your discussion the concept of feedback control and the way in which fertilization of the egg alters the menstrual cycle. STANDARDS: Hypothalamus and Feedback: Maximum 6 pts. __low progesterone or estrogen resulting in positive feedback __secretion of a releasing factor __secretion of pituitary FSH __high level of progesterone or estrogen resulting in negative feedback __causing a decrease in LH releasing factor __causing a decrease in LH __the "pill" and its influence on feedback __influence of stress on feedback Pituitary Hormones: Maximum 6 pts. __FSH secretion by the pituitary gland __the effect of FSH on egg formation __stimulation of estrogen secretion by FSH __LH (or FSH & LH) resulting in ovulation __corpus luteum formation by LH stimulation __progesterone secretion by LH stimulation __decreased LH causing corpus luteum breakdown __formation of corpus albicans Ovarian Hormones: Maximum 4 pts. __estrogen secretion by follicles inhibiting menstrual flow __estrogen secretion initiating endometrial growth __progesterone from corpus luteum promoting further endometrial growth & vascularization __low level of progesterone and estrogen causing menstrual flow Fertilization: Maximum 2 pts. __effect of human or placental chorionic gonadotropin on the pituitary gland __no menstrual cycle Bonus Point: Maximum 1 pt. __mentioning the days or phases of the cycle __a good descriptive diagram __a high estrogen level resulting in stimulation of the hypothalamus to release more LHRF Maximum of 12 if Fertilization and Feedback are not included in the discussion. Maximum of 14 if either Fertilization or Feedback are discussed and not both. ANIMAL REPRODUCTION QUESTION 1989: L. PETERSON/AP BIOLOGY Describe negative and positive feedback loops, and discuss how feedback mechanisms regulate each of the following: a. The menstrual cycle in a nonpregnant human female STANDARDS: Introduction: (describe -/+ feedback loops) 1 pt 1. Definition as an overview of the process: Control mechanism which is regulated through the effect it brings about. 1 + 1 pts 2. Negative feedback: Endproduct acts as an inhibitor of pathway (stimulatory-inhibitory). Seek terms such as inhibit/turn off. Examples: ACTH -> cortisol -> feedback; Lac operon; thermostat metaphor; CO2 respiration, etc. 1 + 1 pts 3. Positive feedback: change in variable amplifies the pathway (stimulatory-stimulatory). Seek terms such as turn on/stimulate/induce. Examples: Oxytocin/birth; LH surge; trypsinogen/trypsin; neural membrane permeability; mating process; sound amplification metaphor; etc. [one point for definition and one point for example] Note: these points might be embedded in Parts A and B. Total of 3 points maximum for introduction out of 5 points possible. Part A: Menstrual Cycle 1 pt 1. Primary function of the cycle as an overall concept: production of gamete and preparation of the uterus. A broad interpretation OK. 1 + 1 + 1 pts 2. Hormones and interactions: look for information that suggests cause and effect and a pathway. Items a-c are complete examples. To earn a point, three targets, hormones, and sources must be given in a logical sequence. Wrong information will void a string of three. The goal is to find physiological relationships and not just terms. a. GnRH (hypothalamus) -> FSH (pituitary) -> estrogen (ovary) -> endometrium b. GnRH (hypothalamus) -> LH (pituitary) -> progesterone (corpus luteum) -> endometrium c. estrogen -> LH surge -> ovulation Research on the regulation of the menstrual cycle is rapidly evolving and textbooks can reflect different philosophies or progress of research. 1 or 2 pts 3. Negative feedback results on hypothalamus/pituitary. Estrogen/progesterone inhibits FSH and LH production at the GnRH (hypothalamus) and pituitary level. If no choriogonadotropic hormone -> estrogen/progesterone levels drop and endometrium stimulus no longer supported - > endometrium lost as cycle begins again and FSH and LH released from inhibition. [2 points for completeness] 1 pt 4. Positive feedback: estrogen -> LH surge. Note: estrogen can be both inhibitory and stimulatory on the hypothalamus/pituitary. Total of 5 points maximum for Part A out of 7 points possible.