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Jess Repro > 4.1: Hormonal control of repro and menstruation > Flashcards

4.1: Hormonal control of repro and menstruation Flashcards

1
Q

Which axis is crucial to producing hormones for gamete production? How does it vary between the genders?

A

Hypothalamic-pituitary-gonadal axis

Feedback mechanisms slightly differ to allow two different patterns of gametes to be produced

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2
Q

Where does the anterior pituitary arise from?

A

Rathke’s pouch

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3
Q

What is the difference in function between the anterior and posterior pituitary?

A

The anterior pituitary is an endocrine gland producing mostly ‘trophic’ hormones (also it’s stimulated hormonally)

The posterior pituitary is nervous tissue (derived from the brain) (requires nervous stimulation)

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4
Q

What is the posterior pituitary’s role in reproduction?

A

Secretes ADH and Oxytocin

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5
Q

Name 4 processes where oxytocin is involved

A

SOLL

  1. social interaction
  2. labour
  3. orgasm
  4. lactation
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6
Q

Name the three most significant hormones involved in reproduction produced by the anterior pituitary. What is their hormonal structure and which cell type secreted each?

A

FSH and LH: secreted by gonadotrophs, glycoprotein hormones

Prolactin: secreted by lactotrophs, polypeptide hormones

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7
Q

How do hormones released by the hypothalamus reach the anterior pituitary and why is this significant?

A

Travel through hypophyseal portal circulation: since this is not the main circulation, they can still have a big impact even with a low concentration

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8
Q

What is the key hormone released by the hypothalamus to control the anterior pituitary? How often is it released?

A

Gonadotrophin releasing hormone (GnRH) - release is ‘pulsatile’, ~once an hour (not a continual release)

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9
Q

Where in the body are FSH and LH most active? What two major things do they do?

A

On the gonads:
1. Gamete production
2. Stimulate secretion of gonadal steroids
(estrogen and progesterone - females, testosterone - males)

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10
Q

How is GnRH secretion influenced? Name one key player

A

Key influencer is the KISS1 neuron which directly stimulates GnRH

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11
Q

What influences the KISS 1 neuron?

A

Externally: Environmental effects: body weight, leptin, glucocorticoid levels, etc

Internally/within repro system: KISS 1 has receptors for the gonadal steroids that are feeding back to the hypothalamus

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12
Q

How do estrogen and testosterone impact GnRH production?

A

Male: Testosterone (-), can only do negative feedback

Female: Estrogen: can do (+) and (-) feedback:

  • Low levels of estrogen - no effect
  • Moderate levels of estrogen reduces GnRH
  • High levels of estrogen increases GnRH secretion (likely a threshold before a positive feedback comes in)
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13
Q

When would you be likely to see high levels of estrogen in a female during her menstrual cycle?

A

Towards the middle of the menstrual cycle

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14
Q

What other hormone is mainly affected by high levels of estrogen?

A

LH (which also increases)

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15
Q

How does progesterone affect GnRH production? What other key hormone in ovulation does it consequentially affect?

A

Inhibitory for GnRH secretion: Increases inhibitory effects of moderate estrogen and prevents positive feedback of high estrogen -> also preventing the LH surge

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16
Q

How do the gonadal steroids estrogen and progesterone SPECIFICALLY reduce the effects of GnRH?

A

Estrogen: reduces the amount of GnRH secreted/pulse

Progesterone: reduces the number of GnRH pulses/ secretions

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17
Q

Name three factors that influence the amount and proportion of LH and FSH secreted (after being stimulated by GnRH)

A

Additional signalling molecules acting on the gonadotrophs:

  1. Gonadal steroids (estrogen, progesterone, testosterone)

And other non-steroidal hormones produced in gonads:

  1. inhibin; generally (-)
  2. Activins; (-) and (+), mechanism varies
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18
Q

What hormone is inhibin more influential on?

A

FSH

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19
Q

When is inhibin secreted in males and females?

A
  1. As the follicle is developing (the more inhibin, the more advanced the follicular development is)
  2. When sperm count is too high; sertoli cells (after being activated by FSH) will also produce inhibin
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20
Q

How is the male’s reproductive apparatus state of being ‘constantly ready for action’ reflected in a male’s general hormonal levels?

A

Hormone levels are constant (medium-long term)

21
Q

What does FSH do in the testis?

A

Binds to the Sertoli cells (next to developing male gamete), and stimulates spermatogenesis

22
Q

What is inhibin a marker of in males and females?

A

Males: Spermatogenesis
Females: advanced follicular growth

23
Q

How does LH act on the testis?

A

Binds to leydig cells which then secrete testosterone which promotes spermatogenesis

24
Q

How does testosterone keep it’s own levels in check?

A

-Ve Feedback to the hypothalamus and the anterior pituitary which inhibits GnRH and LH -> causing testosterone to fall back into a normal range

25
Q

Name three major tissues or processes maintained and/or stimulated by testosterone

A
  1. Stimulates gamete production
  2. Essential to the production of semen as it maintains epididymis, vas deferens, prostate, seminal vesicles and bulbourethral glands
  3. Involved in the development and maintenance of external genitalia and secondary sexual characteristics
26
Q

Name two short-term feedbacks that allow testosterone to respond to environmental factors

A
  1. Circadian rhythm: testosterone is highest in the early morning
  2. Neuronal inputs, stress hormones, etc.
27
Q

What three things happen in the preparation phase in the female reproductive cycle?

A
  1. Follicles growing in the ovary (due to stimulation from FSH and LH)
  2. Uterine lining proliferates in preparation for sperm and implantation of potential embryo
  3. behavioural changes that lead to reproduction… ;)
28
Q

At which point of the cycle is ovulation and what hormone increases right before?

A

Brief period in the middle, brought on by the ‘LH surge’

29
Q

What happens in the ‘waiting’ phase of the menstrual cycle? (and which hormones are involved?)

A

Luteal part: The Corpus luteum (a structure that left behind by once the egg has left during ovulation) maintains the uterine lining for a potential pregnancy by secreting estrogen and progesterone.

Secretory part: refers to the uterus secreting potential nutrients that will help the sperm and the embryo if it implants

30
Q

What is the most common and important type of estrogen in the menstrual cycle

A

Estradiol

31
Q

Which cells bind with FSH and LH in the follicular phase of the menstrual cycle and what is the overall result?

A

FSH -> Granulosa cells
LH -> Thecal cells
Overall stimulates the development of the follicle!

32
Q

What secretes activins and which hormone do they activate the production of?

A

Gonads and other tissues, they feedback to the pituitary to activate FSH secretion

33
Q

Which hormone is more dominant in the first half of the menstrual cycle? Name four things done by this hormone to aid its primary goal

A

Estrogen: Preps the developing follicles to be fertilized, trying to make reproduction more likely to happen

  1. Helps fallopian tube function (for better transport of gametes)
  2. Growth (thickening) and motility of myometrium (muscular layer)
  3. Induces a thin alkaline cervical mucus in preparation for sperm arrival
  4. Changes in vagina, skin, hair and metabolism (including calcium metabolism)
34
Q

Which hormone is more dominant in the second half of the menstrual cycle? Name five things done by this hormone to aid its primary goal

A

Progesterone: modifies the preparations made by estrogen to make them more appropriate for a potential pregnancy (NOT for follicular development)

  1. Thickening the endometrium into a secretory form
  2. Thickening myometrium but reducing its motility
  3. Inducing a thick, acidic cervical mucus (so less sperm can penetrate)
  4. Increased body temp
  5. Metabolic, electrolyte and mammary changes
35
Q

What are the two major layers of the Uterine lining?

A
  1. Endometrium

2. Myometrium (muscular layer)

36
Q

Name the two layers within the uterus’ endometrial layer. Which one is constantly changing throughout the cycle and how?

A
  1. Basal layer: stays the same
  2. Functional layer (inner): constantly changing:
    Proliferates in beginning, waits for embryo to arrive, if no embryo arrives it decreases/degenerates = generating menstrual blood
37
Q

Describe the histological appearance of the uterine lining during the following stages

a) early proliferative
b) late proliferative
c) early secretory
d) late secretory

A

a) glands are spare and straight (little functional layer)
b) Functionalis doubled, glands coiled
c) endometrium is max thickness, pronounced coiled glands (ready to receive embryo!)
d) Glands adopt the characteristic “saw-tooth” appearance (glands are degenerating without an embryo)

38
Q

Why do some follicles develop at different rates than others? How does this result in a dominant follicle?

A

The follicles that contain more granulosa cells have more FSH receptors and therefore respond to FSH more (and develop more), (they’ll also secrete more inhibin). Therefore, follicles that are bigger, respond better and get even bigger = resulting in a dominant follicle

39
Q

What is the outer layer of the follicle called and how is it influenced by follicular growth? Which hormone does it respond to and which does it produce?

A

As the follicles grow the outer/ Thecal layer develops: Contains LH receptors. So more LH -> bigger thecal layer -> produces more estrogen

40
Q

What happens to the levels of LH and FSH directly prior to ovulation? Why

A

Since estrogen levels have been able to rise above a certain threshold level (thanks to continual LH stimulation to the thecal cells): LH undergoes a surge, but FSH doesn’t rise much as there’s been simultaneous secretions of inhibin from the granulosa cells

41
Q

What steroids does the corpus luteum secrete? Include the specific cells involved

A

Estrogen from granulosal luteal cells

Progesterone from thecal luteal cells

42
Q

When does the corpus luteum begin to decrease in size and when does it die?

A

Decreases in size after 7-10 days, dies after about 14

43
Q

What happens hormonally once the corpus luteum has died?

A

The production of gonadal steroids is stopped, including progesterone, this means there is no more inhibition on FSH secretion so FSH levels may rise again, and menses is stimulated (breakdown of uterine lining)

44
Q

Though cycle timings tend to vary amongst individuals, which part of the cycle tends to stay constant?

A

The second half: ovulation - menses tends to stay constant at 14 days

45
Q

What hormone is secreted if conception occurs and what is it secreted by?

A

Developing embryo and placenta secrete human chorionic gonadotrophin

46
Q

What does the hormone HCG ensure?

A

Preserves the corpus luteum: so there will be continued secretions of progesterone and estrogen and the uterine lining stays = the cycle does NOT start again

47
Q

In GENERAL, which cells do FSH and LH act on in both sexes?

A

FSH: immediate gamete support cells

LH: interstitial cells to produce steroids

48
Q

What happens to the levels of FSH and LH during ovulation and why?

A

Although the corpus luteum secretes estrogen it also secretes progesterone, this suppresses estrogen by producing -ve feedback on the hypothalamus and the pituitary to stop the production of FSH and LH.

49
Q

How can LH and FSH respond differently to the same stimulus?

A

Differences in genetic maekup allowing them to have different promoters and activators

Jess Repro (18 decks)

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