2.2 Flashcards
what are and what produces hormones
they are chemical messengers and are produced by endocrine glands
what do hormones do in general
they are secreted into the bloodstream and travel to their target tissue where they bring about a specific response
what do hormones control in reference to reproduction
- the onset of puberty
- sperm production
- the menstrual cycle
what is puberty
the sequence of physical changes in which a child’s body develops into an adults, capable of reproduction
what happens at puberty
the hypothalamus secretes a releaser hormone that targets the pituitary gland
what does the releaser hormone secreted by the hypothalamus (during puberty) stimulate the pituitary gland to release
- follicle stimulators hormone (FSH)
- luteinising hormone (LH) in women
& interstitial cell-stimulating hormone (ICSH)
what does fsh promote
sperm production in the seminiferous tubules
what does icsh stimulate
the interstitial cells to produce testosterone
what does testosterone stimulate and activate
the seminiferous tubules to produce sperm and activates the prostrate gland and the seminal vesicles to produce secretions
when do males stop releasing fsh and icsh
they don’t, they release these hormones from puberty
what type of fertility do men have and what does it mean
continuous, means they are always fertile
what type of fertility do women have & what does it
mean
cyclical, means they are only fertile a few days a month
what happens during negative feedback control of testosterone
high concentrations of testosterone inhibit the pituitary gland from secreting FSH and ICSH so interstitial cells produce less testosterone
how long does the menstrual cycle take
around 28 days
what are the two halves of the menstrual cycle
1st half - follicular phase
2nd half - luteal phase
what happens in the follicular phase
- fsh stimulates development of follicle and production of oestrogen by the follicle
- oestrogen stimulates proliferation of the endometrium to prepare it for implantation. it also affects the consistency of cervical mucus, making it more easily penetrated by sperm
- around day 14, peak levels of oestrogen stimulate a surge in secretion of LH by pituitary gland
- surge of LH triggers ovulation which is the release of an egg from follicle in ovary
- the ovum moves slowly along oviduct and in next 3-4 days fertilisation may occur
what happens in the luteal phase
- LH also stimulates the follicle to develop into the corpus outrun which secrets progesterone
- progesterone promotes further development and vascularisation of the endometrium, preparing it for implantation of a blastocyst if fertilisation occurs
- progesterone causes thickening of cervical mucus, preventing sperm from meeting and protecting the blastocyst from infection
negative feedback (women)
- high levels of progesterone inhibit the secretion of FSH and LH by the pituitary gland
- lack of FSH prevents further follicles from developing
- lack of LH leads to degeneration of the corpusluteum which has a subsequent drop in progesterone levels
- by day 22, these hormones levels are so low that the endometrium breaks down and triggers start of menstruation
what happens to prepare the body for pregnancy
- the corpus luteum doesn’t degenerate and continues to produce progesterone, which maintains the endometrium and prevents miscarriage
- the placenta then takes over the production of progesterone a few weeks into pregnancy
