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1

what is the HPG axis

The hypothalamic–pituitary–gonadal axis (HPG axis) refers to the hypothalamus, pituitary gland, and gonadal glands t regulate development, reproduction and aging

2

where do endocrine glands secrete hormones

into the bloodstream; the hormones travel to and act on other organs or tissues

3

what is the hypothalamus

part of the forebeain that regulates core (homeostatic) functions eg metabolism, growth, reproduction and stress

4

what is a critical component of the reproductive system that is secreted for the hypothalamus

peptide hormone gonadotrophin releasing hormone (GnRH)

5

anterior pituitary is an endocrine gland. made up of different groups of cells which all secrete different hormones. which cells secrete FSH and LH

gonadotrophs

6

gonadotroph proliferation and hormone production is positively regulated by signalling through a what

G-protein coupled receptor GnRHr

7

activation of G-protein coupled receptor causes gonadotrophs to secrete

FSH and LH

8

there are 3 main types of sex steroid. these are..

progesterones, androgens and oestrogen

9

all sex steroids are derived from which common precursor

cholesterol

10

once inside a cell, steroid-receptor complexes bind to steroid response elements on DNA and impact on transcription

T

11

what does oestrogen bind

oestrogen receptor on the gonadotroph

12

binding of oestrogen to its receptor on gonadotroph leads to what

complex translocates into nucleus and mediates negative transcriptional control of target genes through oestrogen response elements

13

binding of oestrogen to the oestrogen receptor on the gonadotroph leads to the reduction of what

production of FSH and LH

14

male and female gonadal cells express inhibins and activins what do these do

bind to receptors on gonadotroph cell and regulate FSH and LH expression

15

feedback control happens at the level of what

pituitary, hypothalamus or testes and ovaries

16

LH and FSH output is predominantly regulated by secretory products of which female organ

ovary

17

which secretory products from ovary exert a depressent effect on gonadotrophin output (FSH and LH)

oestrogens, progesterones and inhibins

18

which secretory products from ovary cause a surge on gonadotrophin output (FSH and LH)

activin, oestradiol

19

oestradiol acts to negatively regulate LH expression at low concs but when its at high concentrations..

it acts to positively regulate expression

20

progesterone has 2 effects. these are

high conc seen in luteal phase - enhances negative feedback of oestradiol
- at certain levels of progesterone, positive feedback of oestradiol is blocked

21

inhibins selectively negatively regulate ... secretion

FSH

22

what cells does FSH act on

granulosa cells

23

what cells does LH act on

thecal cells

24

what is the difference in regulation of gonadotrophs in males

mechanisms similar to females except that there is absense of positive feedback in male (continual production in male)

25

which cells secrete androgens (mainly testosterone)

leydig cells

26

leydig cells secrete androgens that exerts a negative feedback response which causes a decrease in ....

GnRH

27

as in females, what acts at the level of the pituitary to supress FSH secretion

inhibin

28

GnRH is essential for gonadal function. when there is destruction of GnRH neurons what happens

gonadal atrophy

29

when do GnRH pulses begin

puberty

30

what are the 2 ways in which alterations of the output of LH and FSH can be achieved

- increasing or decreasing the amplitude or frequency of GnRH pulses
- modulating the response of gonadotrophs to the pulses