Physiology Flashcards
describe the hypothalamic-pituitary-gonadal axis (HPG)
- hypothalamus= GnRH
- anterior pituitary= LH (high frequency pulses) and FSH (low frequency pulses)
- ovaries= oestrogen and progesterone
- testes= testosterone
how is GnRH released from the hypothalamus?
pulsatile manner
what does GnRH act on in the anterior pituitary?
kisspeptin receptors
what does oestrogen concentration above a certain threshold cause?
increases GnRH pulses driving release of LH
what does an increase in progesterone cause?
reduces the frequency of GnRH pulses causing release of FSH
what does LH surge underpin?
ovulation
what is corpus luteum formed from?
FSH (lipids) which produces progesterone
what is hCG the same as in terms of hormones from the anterior pituitary?
LH
what happens if a developing embryo is not present?
levels of progesterone decrease
FSH (follicle stimulating hormone) causes what in males?
spermatogenesis
FSH causes what in females?
oogenesis (growth of ovarian follicles)
secretion of oestrogen
what happens if oestrogen reaches a certain concentration?
it no longer does negative feedback on the pituitary and hypothalamus but instead exerts positive feedback resulting in LH surge leading to ovulation and formation of the corpus luteum (progesterone)
role of progesterone
decreases pulsatility decreasing LH secretion
needed for expression of enzymes that break down the follicular wall leading to release of the oocyte
which anterior pituitary hormone acts on the theca cell?
LH
which anterior pituitary hormone acts on the granuloma cell?
FSH
role of LH (luteinising hormone) in males
secrete testosterone
role of LH in women
ovulation
progesterone production by corpus luteum