ENDOCRINE CONTROL OF REPRODUCTION Flashcards Preview

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Flashcards in ENDOCRINE CONTROL OF REPRODUCTION Deck (32):
1

where is Gonadotrophin releasing hormone (GnRH) produced?

(in pulses) by median eminence of hypothalamus

2

what is pulsatile secretion?

p

3

where does GnRH diffuse?

to pituitary & causes release of gonadotropins luteinising hormone (LH) & follicle stimulating hormone (FSH)

4

what does overstimulation with GnRH lead to?

to gonadotropin depletion & deficiency

5

what does understimulation with GnRH lead to?

to inadequate gonadotropin production & deficiency

6

what does FSH act on?

acts on the Sertoli cells (only)

7

what does FSH have an effect on?

production of (ABP) for transport of testosterone around blood
effect on germ cells

8

what is ABP?

Androgen Binding Protein (ABP) for transport of testosterone around blood

9

what does LH act on?

acts on the Leydig cells

10

what does LH produce?

produce testosterone

11

what does testosterone stimulate?

germ cells directly but also acts on bone, skin, hair and the accessory sexual organs

12

what is testosterone converted to?

dihydrotestosterone (DHT)

13

what does DHT effect?

effects on prostate and oestradiol – important in epiphysial closure and reproductive system

14

what is FSH negatively regulated by?

by inhibin, produced by S. cells at level of pituitary

15

what is FSH positively regulated by?

regulated by activin & follistatin

16

what is LH negatively regulated by?

by testosterone acting both at level of pituitary and hypothalamus

17

what are the 4 phases of the ovarian cycle?

follicular phase (10-16 days)
ovulatory phase (36 hours)
luteal phase 14 days
menstruation (4-5 days)

18

at what phase does the greatest variability occur?

follicular phase

19

what does the gonadotropin releasing system do?

hypothalamic control LHRH
LH and FSH; pulsatile release

20

what are the ovarian hormones?

oestrogen
progesterone

21

what happens at follicular phase?

FSH acts on 1o and 2o follicles
causes follicular growth
promotes oestradiol secretion from follicles
FSH decreases as oestradiol rises

22

what does LH allow?

1o oocyte completes meiosis I produces 2o oocyte & polar body
Stops at meiosis II metaphase (fertilised)

23

what happens at the ovulatory phase?

oestradiol achieves threshold to switch to +ve feedback
surge of LH
oocyte matures
release of ovum

24

what happens at the luteal phase?

Empty 3o follicle collapses – residual granulosa cells luteinise & invade - endocrine structure - corpus luteum
Secretes oestradiol and progesterone
maintains endometrium
suppresses LH/FSH

25

what happens at the late luteal phase?

corpus luteum involutes
oestradiol and progesterone fall
endometrium not maintained (menstruation)
loss of -ve feedback
FSH rises
begin new cycle

26

what happens if fertilisation occurs?

ovum implants
uterus secretes hCG
hCG maintains corpus luteum
corpus luteum secretes oestradiol and progesterone
endometrium maintained
no menstruation
pregnancy established

27

what are the effects of Oestrogens?

maintenance of bone mass
effects on CNS
effects on vasculature
effects on lipid metabolism
effects on fat distribution
promote insulin secretion
effects on blood clotting

28

what are the roles of Progesterone?

causes body temp to rise
causes change to thick cervical mucus secretion
down regulates oestrogen receptors
exerts a -ve feedback control on the hypothalamus and pituitary

29

what are the effects of menopause?

climacteric, mood changes, loss of libido, hot flushes

30

what is menopause caused by?

by decline in ovarian foll. no’s + reduced responsiveness to gonadotrophins.
Loss of oestrogen
causes increase in LH + FSH

31

what do the vasomotor changes in menopause cause?

hot flushes, night sweats
increased risk of coronary thrombosis

32

what are the other effects of menopause?

reduction in vaginal lubrication rise in pH causes discomfort
Increased risk of osteoporosis
rationale for HRT