11:067:327 Lecture Notes - Lecture 12: Leukocytosis, Atresia, Activin And Inhibin
25 Apr 2016
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Protection outweighs loss of fe and nutrients with menstruation. Conservation of energy - b strassman (1996) Cyclical regression/renewal is energetically less costly than maintaining active site needed for implantation. Increased cycles, estrogen, & ovulation rate contribute to high incidence. Seasonal extended birth control pill, 4 period a year. Synthetic steroids decrease ovulation and endometrial growth. Phase of estrous cycle that begins with cl regression and ends with ovulation. Activated by a threshold level of e2 and low p4. Basal secretion of gnrh fsh/lh follicular growth. Preovulatory release of gnrh lh surge ovulation. Follicular growth e2 increase stimulates gnrh release. After ovulation p4 increase and e2 decrease suppresses. Positive feedback: hormone increases its own rate of secretion. High e2/low p4 (plasma) increased gnrh (surge center) increased fsh/lh (anterior pituitary) increased e2 (follicle) Positive feedback loops are rare in biology. Negative feedback: hormone decreases its own rate of secretion.
