Physiology and Health: Hormonal Control of Reproduction Flashcards
What are hormones?
Chemical messengers that are produced by the endocrine glands
Hormones are released directly into where?
The bloodstream and travel to their target tissue or organ where they have an effect
Hormones control what?
The onset of puberty, sperm production and the menstrual cycle
What happens at puberty?
The hypothalamus in the brain secretes a releaser hormone that targets the pituitary gland
The pituitary gland is stimulated to release what two hormones in women and what one hormone in men?
Follicle stimulating hormone (FSH) and luteinising hormone (LH).
Interstitial cell stimulating hormone (ICSH)
What hormones trigger the onset of puberty in females and in males?
In females, FSH and LH.
In males, ICSH.
In males, FSH and ICSH do what?
FSH promotes sperm production in the seminiferous tubules of the testes.
ICSH stimulates the interstitial cells in the testes to produce the male sex hormone testosterone.
What does testosterone also do?
Stimulates sperm production and activates the prostate gland and seminal vesicles to produce their secretions
Overproduction of testosterone is prevented by what?
A negative feedback mechanism
How does the negative feedback effect work on overproduction of testosterone?
High testosterone level inhibits the secretion of FSH and ICSH from the pituitary gland, resulting in a decrease in the production of testosterone by the interstitial cells
The menstrual cycle takes approximately how many days and begins when?
Takes approximately 28 days.
With the first day of menstruation regarded as day one of the cycle.
What hormones are associated with the menstrual cycle?
Pituitary hormones - FSH and LH
Ovarian hormones - Oestrogen and Progesterone
What happens in the follicular phase (first half of the cycle)?
FSH stimulates the development and maturation of a follicle surrounding the ovum and the production of the sex hormone oestrogen by the follicle
What does oestrogen do during the menstrual cycle?
It stimulates the repair and vascularisation of the endometrium, thickening it and preparing it for implantation. It also affects the consistency of the cervical mucus making it more easily penetrated by sperm.
What does a peak level of oestrogen stimulate?
A surge in the secretion of LH by the pituitary gland
In the luteal phase (second half of the cycle), this surge in LH triggers what?
Ovulation
What is ovulation?
The release of an egg (ovum) from a follicle in the ovary
When does ovulation occur?
Around the mid-point of the menstrual cycle
What does LH also stimulate during the menstrual cycle?
The development of the corpus luteum from the follicle and stimulates the corpus luteum to secrete the sex hormone progesterone
What does progesterone do?
Promotes further development and vascularisation of the endometrium preparing it for implantation if fertilisation occurs
High levels of oestrogen and progesterone inhibit what?
The secretion of FSH and LH by the pituitary gland, which prevents further follicles from developing
The inhibition of FSH and LH by high levels of oestrogen and progesterone is an example of what?
Negative feedback control
The lack of LH leads to what?
The degeneration of the corpus luteum with a subsequent drop in progesterone level, leading to menstruation
If fertilisation does occur, what happens to the corpus luteum?
It does not degenerate and progesterone level remains high
