2) Control of Reproductive Processes Flashcards by Lauren Croft

What hormones does the hypothalamus produce?

Gonadotrophin releasing hormone (GnRH)
Prolactin releasing hormone (PRH)
Prolactin inhibiting hormone (PIH)

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What hormone does the posterior pituitary produce?

Oxytocin

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What hormones does the anterior pituitary produce?

Follicle stimulating hormone (FSH)
Luteinising hormone (LH)
Prolactin

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What hormones do the testes produce?

Testosterone
Inhibin
Mullerian inhibiting hormone (MIH)

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What hormones do the ovaries produce?

Oestrogen
Progesterone
Inhibin

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What hormones does the placenta produce?

Human chorionic gonadotrophin (hCG)
Human placental lactogen (hPL)
Oestrogen
Progesterone

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Where does the anterior pituitary arise from?

Rathke’s pouch

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What type of tissue does the posterior pituitary arise from?

Nervous tissue

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Which hormones do the gonadotrophs secrete?

FSH - growth of reproductive system

LH - sex hormone production

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Which hormones are secreted by corticotrophs?

ACTH - secretion of glucocorticoid, mineralocorticoid & androgens
MSH - Melanocyte stimulating hormone, production & release of melanin

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Thyroid stimulating hormone is released by which type of cell?

Thyrotrophs

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What do somatotrophs secrete?

Growth hormone - Promotes growth, lipid & carbohydrate metabolism

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What do lactotrophs secrete?

Prolactin - secretions of oestrogen, progesterone, milk production

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Which hormone controls the release of FSH & LH?

Gonadotrophin releasing hormone (GnRH)
produced in hypothalamus
travels to anterior pituitary
via hypophyseal portal vessels

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What reduces GnRH release?

Testosterone
Oestrogen intermediate concentration 
 - lowers amount secreted per pulse
Progesterone
- increases inhibitory effect of oestrogen
- lowers frequency of pulses

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What increases GnRH release?

Oestrogen ALONE at high concentrations

promotes GnRH surge
progesterone prevents this

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What is the function of Inhibin?

Reduces the amount of FSH secreted in response to GnRH

Acts on anterior pituitary

Which cells produce inhibin?

Developing follicles (granulosa cells) in ovary
Seminiferous tubules (sertoli cells) in testis

What is the effect of LH in the testes?

Acts on Leydig cells
Promote secretion of testosterone

LH effects enhanced by Prolactin & Inhibin

What are the actions of testosterone?

Acts on Sertoli cells to promote spermatogenesis

Acts in the body to maintain male reproductive system

What is the effect of FSH in the testes?

Maintains sertoli cells, makes them responsive to testosterone

During the antral phase of follicular development, what is the role of FSH & LH?

LH binds to theca interna cells, produce androgens

FSH binds to granulosa cells, produce enzymes - androgens > oestrogen

During the pre-ovulatory phase of follicular development, what is the role of FSH & LH?

Follicle producing high amount of oestrogen
LH receptors develop on granulosa cells
[High] oestrogen +vely feeds back
LH surge
Stimulates ovulation
FSH still being inhibited by Inhibin

During the luteal phase of follicular development, what is the role of FSH & LH?

LH stimulates corpus luteum,
Produces oestrogen & progesterone
Progesterone prevents +ve & enhances -ve feedback
Prevents new follicles developing, decreases FSH

What are the 2 broad effects of gonadal steroids (testosterone)?

Determinative effects - qualitative, only partly reversible | Regulatory effects - highly reversible, rely on continuous hormonal stimulation

What are the determinative actions of testosterone?

``` Increase muscle size & mass, vocal cords, bones Deepening of voice Facial & body hair Increased stature Growth of penis ```

What are the regulatory actions of testosterone?

Maintenance of male internal genitalia Metabolic (anabolic) action Behavioural effects - aggression, sexual activity

What are the actions of oestrogen?

``` Fallopian tube function Thickening of endometrium Growth & motility of myometrium Thin alkaline cervical mucus Vaginal changes Changes in skin, hair & metabolism Calcium metabolism ```

What are the actions of progesterone on oestrogen primed cells?

Further thickening of endometrium into secretory form Thickening of myometrium, but reduction of motility Thick, acid, cervical mucus Changes in mammary tissue Increased body temperature Metabolic (mild catabolic) changes Electrolyte changes

List the phases of the menstrual cycle

Menses 0-5 Follicular phase 5-14 Ovulation 14 Luteal phase 14-28

What happens during the follicular phase?

Stimulation of development of follicle in ovary Uterus prepared for sperm transport & implantation of conceptus Steady rise of oestrogen

What happens during pre-ovulation/ovulation?

LH surge stimulates ovulation Brief period of fertility Formation of corpus luteum Rapid drop in oestrogen

What happens during the luteal phase?

LH maintains corpus luteum in ovary Wait to see if there's a pregnancy Actions of progesterone on oestrogen primed cells (increased progesterone)

What happens when there is a sudden fall in progesterone & oestrogen levels? (usually around day 28)

Secretory epithelium of endometrium collapses Apoptotic cell death Dead tissue shed as menstrual bleed Spiral arteries contract to reduce bleeding

Describe the hormonal changes during the beginning of the menstrual cycle

Oestrogen, progesterone & inhibin levels low GnRH secretion is released from inhibition LH & FSH rise, FSH more as low Inhibin levels release FSH from selective inhibition at the ant. pituitary

Describe the hormonal changes during days 12-14 of the cycle

+ve feedback of rising oestrogen stimulates an LH surge LH surge produces ovulation Oestrogen levels fall dramatically Corpus Luteum forms

Describe the hormonal changes after ovulation

LH promotes oestrogen & progesterone secretion from corpus luteum As corpus luteum grows, more steroids are secreted Rising oestrogen does not +vely feedback on LH because progesterone levels also rising

Describe the hormonal changes 14 days after ovulation

Absence of pregnancy CL regresses Progesterone & oestrogen fall - menses Relieves inhibition on GnRH, LH & FSH - development of new follicle

What hormonal changes take place if conception has occurred?

Implanted embryo develops placenta - secretes hCG hCG prevents regression of CL CL secretes oestrogen & progesterone supports early weeks of pregnancy (up to 12-14)

How is testosterone release regulated by feedback?

Testosterone rise: GnRH inhibited, reduced LH & FSH LH & FSH reduced further by testosterone reducing sensitivity of gonadotrophs to GnRH Testosterone levels fall back