w5 - reproduction/sex steroid axis: physiology ad biochem

Question 1

6 key repro hormones

Answer 1

GnRH 
LH 
FSH 
Oestrogen 
Progesterone 
Testosterone

Question 2

effect of FSH in 1) males, 2) females

Answer 2

1 - testes do spermatogenesis

2- growth of ovarian follicles (oogenesis), causes ovary to secrete oestrogen

Question 3

effect of LH in 1) males, 2) fema

Answer 3

1 - testes secrete testosterone

2- causes ovulation, progesterone producion (by corpus luteum)

Question 4

what is responible for the release of FSH and LH (from ant. pit)

Answer 4

Gonadotrophin releasing Hormone (GnRH)

Question 5

GnRH comes from

Answer 5

hypothalamus

hypothalamus - pit - gonadal axis

Question 6

GnRH is secreted constantly in females, but pulsatile in males t.f

Answer 6

false
males - constant pulsatile manner

females - freq. varies during menstrual cycle

Question 7

High-frequency GnRH pulses stimulate __ pulses whereas low-frequency pulses are required for ___ release

Answer 7

LH

FSH

Question 8

conc of what will incr GnRH pulsatility, driving release of LH

Answer 8

oestrogen

Question 9

incr in ___ conc reduces the freq of GnRH pulses

Answer 9

progesterone

Question 10

onset og puberty maturation is assoc with a steady acceleration in __ ___

Answer 10

GnRH pulsatility

Question 11

activation of GnRH pulse frequency is a central mechanism associated with delayed puberty, what/when to consider for boys/girls

Answer 11

females: no period by age 15
males: no testicular development by age 14

Question 12

other than progesterone and oestrogen, what else regulates GnRH pulsatility

Answer 12

kisspeptin

Question 13

menstrual cycle, when is LH/progesterone/FSH/estradiol at their highest

Answer 13

LH + FSH + Estradiol all just before ovulation

Progest - during LH

Question 14

FSH stimulates growth of ___ ___(associated with an increase in oestrogen levels)
Rising oestrogen levels in turn exert negative feedback regulation (level of hypothalamus and pituitary) to lower ___ (temporarily)
Once oestrogen reaches a certain concentration it exerts positive feedback regulation resulting in an increase in ___ and the LH ‘surge’
LH surge eventually leads to ____ and regulates the formation of the ___ ___ and progesterone production and secretion
Increasing progesterone decrease LH secretion by influencing __ __

Answer 14

ovarian follicles

FSH

FSH

ovulation
corpus luteum

GnRH pulsatility

Question 15

Endometrium thickens under the influence of ___ and a becomes a secretory tissue under the influence of ___

Answer 15

oestrogen

progesterone

Question 16

a follicle consists of an oocyte surrounded by folliciular cells (granulosa and theca cells) explain what happens during Follicular phase

Answer 16

incr in follicular cells

accumulation of follicular fluid

Question 17

LH surge precedes ovulation by approx.

Answer 17

34-36hrs

Question 18

how does LH surge come about

Answer 18

oestrogen rises >200pg/ml, increases GnRH pulsatility which causes LH surg

Question 19

formation of corpus luteum occurs due to transformation of oocytes to luteal cells t.f

Answer 19

false

follicular cells - theca + granulosa

Question 20

LH stimulates angiogenesis which ensures efficient delivery of cholesterol, why is this important

Answer 20

cholesterol i a substrate for prog. synthesis

LH also stimulates enzymes involved in this conversion

Question 21

functiion of oestrogen

Answer 21

Increase the thickness of the vaginal wall
Regulate the LH surge
Reduce vaginal pH through increase in lactic acid production
Decrease viscosity of cervical mucus to facilitate sperm penetration

Question 22

function of progesterone

Answer 22

progesterone = pro gestation

endo wall thickness maintained
relaxes myometrium,

Question 23

testosterone is synthesised from ___, due to LH binding to receptos on __ cells

Answer 23

cholesterol

LEydig

Question 24

testosterone stimulates spermatogenesis through which cells

Answer 24

Sertoli cells

Question 25

in testes, which cell expresses the FSH receptor

Answer 25

sertoli cells

FSH stimualtes prodution of ABP (androgen binding proein) by sertoli cells