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Endocrine > reproduction/sex steroid axis: physiology and biochem > Flashcards

reproduction/sex steroid axis: physiology and biochem Flashcards

1
Q

what gonadotrophic hormones does the pituitary gland secrete?

A
  • FSH

- LH

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2
Q

what hormone produced by the hypothalamus triggers the pituitary to secrete LH/FSH?

A

GnRH

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3
Q

what is the role of FSH in males?

A

-causes the testes to produce sperm (spermatogenesis)

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4
Q

what is the role of FSH in females?

A

-causes the growth of the ovarian follicles (oogenesis) and it causes the ovary to secrete oestrogen

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5
Q

what is the role of LH in males?

A

-causes the testes to secrete testosterone

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6
Q

what is the role of LH in females?

A

-causes ovulation and it causes progesterone to be produced by the Corpus Luteum

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7
Q

what synthesizes and releases GnRH in the hypothalamus?

A

GnRH neurons within the hypothalamus

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8
Q

what is GnRH responsible for?

A

the release of LH and FSH

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9
Q

in what manner is GnRH released?

A

-a pulsatile manner

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10
Q

how is GnRH released in females compared to males?

A
  • in males GnRH is secreted in pulses at a constant frequency
  • in females the frequency of the pulses vary during menstrual cycle
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11
Q

what do high frequency GnRH pulses stimulate?

A

-LH

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12
Q

what do low frequency GnRH pulses stimulate?

A

-FSH

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13
Q

what effect does estrogen have on GnHR pulses?

A

-once oestrogen reaches a certain threshold then it will increase the GnRH pulsatility driving the release of LH

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14
Q

what effect does progesterone have on GnRH pulses?

A

-it decreases them

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15
Q

what hormones regulate GnRH pulsatility?

A

-oestrogen and progesterone

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16
Q

do GnRH producing neurons contain estrogen and progesterone receptor?

A

no- the receptors for estrogen and progesterone are found on kisspeptin neurons which then influence GnRH neurons

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17
Q

what are the 2 phases of the menstrual cycle?

A
  • follicular phase

- luteal phase

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18
Q

how long is the average menstrual cycle?

A

28 days

19
Q

what day does ovulation occur in the menstrual cycle?

A

14

20
Q

what occurs in the follicular phase?

A

-follicular growth

21
Q

what occurs in the luteal phase?

A

-the corpus luteum is formed under the influence of LH

22
Q

what phase of the menstrual cycle is more variable?

A

follicular phase

23
Q

describe the affect of hormones on the menstrual cycle?

A
  • FSH stimulates growth of ovarian follicles, increasing oestrogen levels
  • rising oestrogen levels exert negative feedback regulation to temporarily lower FSH
  • once oestrogen reaches a certain concentration it exerts a positive feedback resulting in an increase in FSH and a surge of LH
  • LH surge leads to ovulation and regulates the formation of the corpus luteum and progesterone production/secretion
  • increasing progesterone increases the frequency of the GnRH pulses and so decreases LH levels
24
Q

what effect does FSH have on the follicular cells?

A

-increases the number of follicular cells and accumulation of follicular fluid both resulting in an increase in diameter and overall size of the follicle

25
Q

what effect does oestrogen have on the endometrium?

A

causes it to thicken

26
Q

what part of the follicle is highlighted blue?

A

antrum

27
Q

what part of the follicle is highlighted blue?

A

oocyte

28
Q

what part of the follicle is highlighted blue?

A

zona pellucida

29
Q

what part of the follicle is highlighted blue?

A

zona granulosa

30
Q

what part of the follicle is highlighted blue?

A

theca interna

31
Q

how is oestrogen produced in the follicles?

A
  • LH allows cholesterol to be converted into androgens in the Theca cells
  • FSH then converts androgen into estrogen in the granulosa cell
32
Q

True or False follicle growth is always controlled by FSH

A

False

In early stages follicles are gonadotrophic independant and so do not require FSH

In later stages follicles are gonadotrophic dependant and so require FSH

33
Q

when does ovulation occur after LH surge?

A

34-36 hours after

34
Q

what hormone stimulates the formation of the corpus luteum?

A

LH

35
Q

how does LH cause an increase in progesterone production?

A

-LH stimulates enzymes involved in conversion of cholesterol to progesterone

36
Q

what is the effect of estrogen on vaginal pH?

A

-reduces vaginal pH through increase in lactic acid production

37
Q

what effect does estrogen have on viscosity of cervical mucus?

A

-it decreases viscosity of cervical mucus to facilitate sperm penetration

38
Q

what role does progesterone have on pregnancy?

A

-it maintains pregnancy

39
Q

what effect does progesterone have on the endometrium?

A

-it maintains the thickness of the endometrium

40
Q

what effect does progesterone have on mucus?

A

-it is responsible for infertile thick mucus to prevent sperm transport and help prevent infection

41
Q

what effect does progesterone have on myometrium?

A

-relaxes the myometrium

42
Q

how long does spermatogenic process take place?

A

70 days

43
Q

what is most of testosterone taken up by?

A

-Sertoli cells (90%)

44
Q

what role does testosterone play during spermatogenesis?

A
  • maintains the integrity of the blood testes barrier

- releases mature spermatozoa from Sertoli cells by influencing peritubular myoid cells

Endocrine (53 decks)

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