Sex Hormones W4 Flashcards
(22 cards)
What is secreted by the hypothalamus and what does it do
GnRH - Gonadotropin-Releasing Hormone.
Stimulates the anterior pituitary gland to release LH and FSH
Act on the testes and ovaries to regulate gait production gamete
2 main structural components of the testes
Interstitial cells = fill the gaps between the seminiferous tubules and produce testosterone
Seminiferous tubules = site of sperm production
LH stimulates….. (Men)
Stimulates interstitial cells in testes to produce testosterone which them drives spermogenesis and maintain 2ndary sex characteristic
FSH stimulates …. (Men)
Stimulates seminiferous cells which are found in the tubules and stimulate these cells to release androgen binding ATP. This enhances thr ability of the sperm to bind to testosterone
What is in the Ovaries
In each there are follicles and each month some will mature into primary follicles and continue maturing but only one will ovulate
Menstrual cycle phases (2)
- Folicular
- Luteal
Folicular phase
The first phase starting on day one until ovulation ( day 14 )
Involves the growth and maturation of ovarian follicles
LH and FSH are released
Oestrogen rises
Follicles begin to mature but one becomes dominant
Urine lining thickens
FSH secretion women and follicles
Secreted primarily in response to low oestrogen
When oestrogen rises, FSH will fall
As follicles mature they produce more oestrogen and so this rise will cause decrease in FSH
Peripheral effects of oestrogen
occur in various tissues and organs outside the central reproductive system
- Maintains bone density and reduces the risk of osteoporosis.
- Enhances collagen production, skin elasticity, and hydration.
- Improves cholesterol levels.
- Maintains muscle mass
After 10 days what happens for women
Oestrogen continue to rise and follicles matures
After these 10 days the oestrogen rises and will have positive feedback and stimulate release of LH
At low concentrations, oestrogen will……. LH secretion, but at high concentrations oestrogen will……LH secretion
Inhibit
Stimulate
What triggers ovulation of the most mature follicle
Spike in LH conc
So LH triggers ovulation and an egg is released after
After ovulation (not hormones)
The follicle will turn into corpus luteal - a dead follicle
It will slowly degrade but still has purpose as it secretes oestrogen, progesterone and inhibin
oestrogen, progesterone and inhibin levels (ovulation)
Oestrogen increase until ovulation and then drop slightly
inhibin wasn’t present until after ovulation and then begins to increase
progesterone levels were low until after ovulation during the luteal phase.
At 21 days
Progesterone is increasing
Inhibin is increasing and has neg feedback and will inhibit the secretion of FSH - we dont want anymore follicles to mature
Oestrogen is still detectable
As the 2ndary luteal corpus develops….
Inhibin secretion will suppress FSH
Most important hormoe in the luteal phase ?
Progesterone
Has many functions including having a neg feedback on hypothalamus, inhibiting GnRH secretion
Progesterone increases slowly after ovulation and oestrogen decreases and this suppresses GnRH
Main effect of progesterone
Stimulate endometrial growth and endometrial lining of the uterus which sheds each month or it is where the egg implants if fertilised
If there is no fertilisation
Corpus luteum in the ovary will degenerate, allowing a new set of follicles to mature and its hormones will also decrease
When the corpus degenerates…
Progesterone will decrease and so cannot inhibit GnRH secretion and so this will increase and allow a new menstrual cycle to occur
The decrease in progesterone and oestrogen causes
Uterus to shed as cannot maintain the lining - have a period and a new cycle begins
Prolactin inhibition
Inhibited by dopamine and stimulates milk secretion but also has effects in:
- decreasing gonadal activity by decreasing GnRH
- hyperprolactinaemia
