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ANIMAL REPRODUCTION QUESTION 1979: L. PETERSON/ECHS 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. 1 - low progesterone or estrogen resulting in positive feedback 1 - secretion of a releasing factor 1 - secretion of pituitary FSH 1 - high level of progesterone or estrogen resulting in negative feedback 1 - causing a decrease in LH releasing factor 1 - causing a decrease in LH 1 - the "pill" and its influence on feedback 1 - influence of stress on feedback Pituitary Hormones: Maximum 6 pts. 1 - FSH secretion by the pituitary gland 1 - the effect of FSH on egg formation 1 - stimulation of estrogen secretion by FSH 1 - LH (or FSH & LH) resulting in ovulation 1 - corpus luteum formation by LH stimulation 1 - progesterone secretion by LH stimulation 1 - decreased LH causing corpus luteum breakdown 1 - formation of corpus albicans Ovarian Hormones: Maximum 4 pts. 1 - estrogen secretion by follicles inhibiting menstrual flow 1 - estrogen secretion initiating endometrial growth 1 - progesterone from corpus luteum promoting further endometrial growth & vascularization 1 - low level of progesterone and estrogen causing menstrual flow Fertilization: Maximum 2 pts. 1 - effect of human or placental chorionic gonadotropin on the pituitary gland 1 - no menstrual cycle Bonus Point: Maximum 1 pt. 1 - mentioning the days or phases of the cycle 1 - a good descriptive diagram 1 - 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/ECHS 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 borad 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 physio- logical 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 (hypo- thalamus) 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.