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30 Cards in this Set

  • Front
  • Back
Where is the greatest number of GnRH producing neurons found?
The arcuate nucleus.
What pulse frequency of GnRH is needed to suppress gonadotropin secrection?
5 pulses/hour
What's the half-life of LH?
30 minutes
What's the half-life of FSH?
3.9 hours
On what cells does LH primarily act?
The ovarian theca cells to induce steroidogenesis.
What does FSH act to promote?
Follicular growth
What influences LH receptors to appear on granulosa cells after the follicle matures?
FSH and estradiol
What is the cascade mechanism responsible for transmitting the intracellular signal that LH or FSH has bound?
cAMP is the intracellular signal for both FSH (granulosa cells) and LH (theca cells)
During what phase of the menstrual cycle can we find Inhibin-B?
Inhibin-B predominates during the follicular phase.
During what phase of the menstrual cycle can we find Inhibin-A?
Inhibin-A predominates during the luteal phase.
What stimulates inhibin production, and what cells produce inhibin?
FSH stimulates inhibin production by granulosa cells.
What stimulates activin production, and what cells produce activin?
FSH stimulates activin production by granulosa cells.
What does activin do?
Activin augments FSH activity including: increasing FSH/LH receptor expression, aromatization, inhibin/activin production.
What does inhibin do?
Inhibin enhances LH stimulated androgen synthesis.
What does the dominant follicle secrete and why?
It secretes estrogen and inhibin, which leads to decreased FSH production by the gonadotroph. Because the dominant follicle has the most FSH receptors, it can survive in the low FSH environment while neighbor follicles die.
What causes the LH surge?
Estrogen: after the estradiol levels reach approx 200 pg/ml for 2 days, there is positive feedback that leads to the LH surge.
At what levels of the hypothalamic-pituitary axis does estrogen act in a positive feedback manner to cause the LH surge?
Presumably both the pituitary and hypothalamic levels.
What does the LH surge cause?
1. Resumption of meiosis.
2. Ovulation within 12-16 hours of the peak of the LH surge.
3. Leutinization of the follicle (now the corpus luteum), which leads to a shift in steroidogenesis in favor of progesterone production.
What happens to the levels of LH and FSH during the luteal phase?
The decrease because of the negative feedback of progesterone and estradiol.
What happens to the corpus luteum at the end of the luteal phase?
It produces decreasing amounts of progesterone, estradiol, and inhibin. This leads to a loss of negative feedback on the hypothalamic-pituitary axis.
When is the mentrual interval the most irregular?
In the 2 years after menarche and in the 3 years before menopause.
What is the most variable portion of a woman's cycle?
The follicular phase.
What are the two layers of the endometrium?
Stratum Basalis & Stratum Functionalis
What does the stratum functionalis consist of?
An underlying stratum spongiosum and the stratum compactum.
Which layer of the endometrium grows and is shed during menstruation?
The stratum functionalis.
What hormone influences the stratum functionalis to proliferate?
How does progesterone influence the stratum functionalis?
It causes secretion of glycogen rich material into the glandular lumens.
What does decidualization refer to?
It is the change of the endometrial stromal cells to become more polygonal while accumulating an eosinophilic substance rich in glycogen and lipid.
The prolonged vasoconstriction that occurs following the shedding of the endometrium is thought to be mediated by what?
Prostaglandins produced by glandular cells and proteins such as Endothelin-1 derived from stromal cells.
On what enzymes is shedding of the endometrial tissue dependent upon?
The matrix metalloproteinases, which digest the extracellular matrix. Progesterone withdrawl leads to stromal cell production of these enzymes.