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Flashcards in 2.1 Deck (40):
1

Where is the pituitary gland located?

Immediately beneath the hypothalamus in the pituitary fossa

2

Two names for ant pit

pars distalis
Adenohypophysis

3

Where does the ant pit arise

From Rathke's pouch - not nervous tissue

4

How does ant pit connect to the hypothalamus?

Superior hyphyseal artery

5

What hormones does ant pit produce?

Prolactin, GH, TSH, FSH, LH, ACTH

6

Two names for the post pit

pars nervosa
Neurohypophysis

7

How can you tell the difference between the adenohypophysis and the neurohypophysis in histology

Ant pit stains darker and post pit stains lighter

8

What is the post pit derived from

Nervous tissue, outgrowth of hypothalamus

9

What does the post pit secrete

ADH, oxytocin

10

How does it connect to the hypothalamus?

Hypothalmic neurones pass through the neural stalk addend in the post pit.

11

What are the glycoproteinhormones that the ant pit secretes? Cell type producing these?

FSH - gonadotrophs
LH - gonadotrophs
TSH -thyrotrophs

12

What are the polypeptide hormones that the ant pit secretes? Cell type producing these?

ACTH - corticotrophs
GH - somatotrophs
Prolactin - lactotrophs

13

What 3 repro hormones doe stye hypothalamus produce?

Gonadotrophin releasing hormone GnRH
Prolactin inhibiting hormone (dopamine)
Prolactin releasing hormone

14

What hormones do the testes and ovaries secrete?

Testes:
Testosterone
MIH
Inhibin
Ovaries:
Oestrogen
Progesteron
Inhibin

15

How is gonadotrophin secretion controlled by the hypothalamus?

Ant pit secretion is controlled by hypophysiotrophic releasing/inhibitory hormones produced by neurosecretory neurones in the hypothalamus.
These pass to the ant pit via the hypophyseal portal circulation.
Arterial blood in hypothalamus picks up the reeling hormones and moves into hypophyseal portal circulation.

16

Why does the hypothalamus not need to secrete much releasing hormone?

Goes into hypophyseal portal circulation only to ant. pit. which means it doesn't get diluted due to direct blood supply.

17

Give characteristics of hypothalamic releasing hormones.

Secretion in pulses according to internal clock.
Synchronised with external signals.
Act on specific receptors.
Transduce signals via second messengers.
Stimulate synthesis and release of pituitary hormones.
Stimulate hyperplasia and hypertrophy of target cells.
Regulates own receptor.

18

Describe GnRH secretion and therefore FSH and LH release.

Pulsatile
Burst of secretion once an hour..

19

What circulating hormones feedback on GnRH secretion?

Testosterone
- Reduces secretion
Oestrogen at Intermediate conc.
- Reduces secretion so lowers the amount secreted per pulse.
Progesterone
- Increases the inhibitory effect of moderate oestrogen by lowering the frequency of pulses.
Oestrogen alone at high conc.
- Promotes release of GnRH producing LH surge.
- Progesterone prevents positive feedback of high oestrogen.

20

What are the actions of FSH and LH

Steroidogenesis
- Oe and Pro in females
-Test in males
Gonadal growth
Gametogenesis

21

What else influences GnRH secretion?

Environmental effects
Body weight

22

What kind of receptors do LH/FSH bind to?

GsPCR on gonads

23

What is the function of inhibin?

Reduce the amount of FSH secreted in response to GnRH.
Secretion related to developing gametes - more gametes developed, more inhibit released.

24

Draw HPG axis in males

-

25

What is the action of LH in males?

Stimulate testosterone secretion from leydig cells.

26

What hormones enhance the effect of LH?

Prolactin and Inhibin

27

Describe the action of testosterone.

Acts on sertoli cells to promote spermatogenesis.
Acts to maintain the male repro tract.

28

What does FSH do in males?

Maintains setoli cells making them responsive to testosterone.
Stimulate sertoli cells to produce androgen binding globulin, which keeps testosterone in the seminiferous tubules, and inhibit, which helps support spermatogenesis.

29

Describe the operation of the whole HPG axis in males

Male must constantly produce sperm.
This requires constant appropriate levels of FSH, LH and testosterone, achieved by negative feedback.
If testosterone levels rise, this inhibits GnRH secretion so reduced LH/FSH so reduced testosterone and spermatogenesis.
If spermatogenesis proceeds to rapidly, inhibit levels rise.
This reduces secretion of FSH by acting on gonadotrophs in ant pit.
Testosterone is affected by
Circadian rhythm - highest in morning
Environment

30

What are the 3 phases of the menstrual cycle?

Antral (follicular)
Pre-ovulatory
Luteal

31

What cells do LH and FSH bind to in the ovaries? What are their function in the astral phase?

LH --> Theca interna --> produce andtrogens (androstenedione)
FSH --> Granulosa cells --> produce enzymes to convert androgens to oestrogen

32

Describe oestrogen secretion in the antral phase

As follicle grows, more oestrogen is produced for given amount of LH/FSH.
Oestrogen at low levels exerts a negative feedback on gonadotrophin release.

33

What are the functions of oestrogen in the astral phase?

Fallopian tube function
Thickening of endometrium
Growth and motility of myometrium
Thick alkaline cervical mucus
Vaginal changes
Calcium metabolism

34

Describe the pre-ovulatory stage.

Follicle has grown and is producing a high amount of oestrogen --> Positive feedback enhancing LH release.
LH receptors develop on outer layers of granulosa cells.
LH surge produce:
Stimulates ovulation
Weakens theca externa with increased collagenase activity.
FSH is still inhibited by inhibin --> LH increases more.

35

Describe the luteal phase.

Remains of follicle reorganise into corpus luteum.
LH stimulates corpus luteum to secrete progesterone and oestrogen.
Progesterone prevents high oestrogen from producing GnRH surge by enhancing negative feedback.
Also reduces frequency of GnRH pulses.
As corpus luteum grows, more steroids are produced for given [LH]

36

What are the actions of progesterone on oestrogen primed cells?

Further thickening of endometrium into secretory form.
Thickening o myometrium.
Thick, acid cervical mucus.
Changes in mammary tissue.
Increased body temp.
Metabolic changed.
Electrolyte changes.

37

What happens to the HPG axis after menopause?

Oestrogen secretion dramatically reduces.
FSH levels rise dramatically
LH levels rises
GnRH levels rise
As negative feedback is reduced..

38

Why, after monpause, do FSH levels rise more than LH levels?

No inhibit from ovary so selective inhibition of FSH by inhibit no longer occurs allowing FSH to rise.

39

Give the determinative effects of testoterone

Partly/non reversible
Increase size and mass of muscles, vocal cords, bones
Deepening of voice
Facial and body hair
Increased stature
Growth of penis.

40

Give the regulatory effects of testosteron

Highly reversible and rely on continuous hormonal stimulation.
Maintenance of male internal genitalia
Metabolic action
Behaviour:
Agression/sexual