2.2 Flashcards
(46 cards)
what are hormones
•chemical messengers produced by endocrine glands which are secreted directly into the bloodstream and travel to their target tissue where they bring about a specific response
what do hormones control?
•the onset of puberty, sperm production, and the menstrual cycle
what is puberty?
•the sequence of physical changes in which a child’s body develops into an adult’s body, capable of reproduction
what happens at puberty
•the hypothalamus secretes a releaser hormone that targets the pituitary gland
what two hormones does the releaser hormone stimulate to release?
•follicle-stimulating hormone (FSH)
•luteinising hormone (LH)
-only in women-
•interstitial cell-stimulating hormone (ICSH)
-only in men-
what hormones trigger the onset of puberty and what do they do?
•FSH and LH trigger the start of menstrual cycles in women
•FSH and ICSH trigger the production of sperm in men
what is the function of the FSH hormone?
•FSH promotes sperm production in the seminiferous tubules
what is the function of the ICSH hormone?
•ICSH stimulates the interstitial cells to produce testosterone
describe the mens fertile state as these hormones (FSH & ICSH) are released
•males continue to release FSH and ICSH hormones and remain continuously fertile from puberty onwards
describe negative feedback control
•high concentrations of testosterone inhibit the pituitary gland from secreting FSH and ICSH so interstitial cells produce less testosterone
how long does a menstrual cycle approximately last?
•28 days with the first day of menstruation regarded as day one of the cycle
what are the two halves of the menstrual cycle known as?
•first half: follicular phase
•second half: luteal phase
what does FSH stimulate?
(follicular phase)
•development of the follicle and the production of oestrogen by the follicle
what does oestrogen stimulate?
(follicular phase)
•proliferation of the endometrium to prepare it for implantation
•also affects cervical mucus making it thinner which makes it eaiser for the sperm to penetrate
what is the mid-point of the menstrual cycle?
(follicular phase)
• approximately day 14 of the 28 day cycle
what happens at the mid-point of the menstrual cycle
(follicular phase)
•oestrogen levels are at their peak
•peak levels of oestrogen stimulate a surge in secretion of LH by the pituitary gland
what does the surge of LH trigger?
(follicular phase)
•the surge of LH triggers ovulation which is the release of an egg (ovum) from a follicle in the ovary
describe where the egg travels during ovulation
(follicular phase)
•the ovum moves slowly along the oviduct and in the next 3-4 days fertilisation may occur
what does the surge of LH stimulate?
(luteal phase)
•stimulates the development of the corpus luteum from the follicle which secretes progesterone
what does the corpus luteum secrete?
•progesterone
what does progesterone promote?
(luteal phase)
•further development and vascularisation of the endometrium, preparing it for implantation of a blastocyst IF fertilisation occurs
what does progesterone do to cervical mucus?
(luteal phase)
•causes thickening of the cervical mucus, preventing sperm from entering and protecting the blastocyst from infection
describe negative feedback inhibition
•High levels of progesterone and ostrogen inhibit the pituitary gland from secreting of FSH and LH
• The lack of FSH prevents further follicles from developing
• The lack of LH leads to degeneration of the corpus luteum which has a subsequent drop in progesterone levels
• By day 22, these hormone levels are so low that the endometrium breaks down and triggers the start of menstruation
What does the hypothalamus produce to trigger the onset of puberty?
•releaser hormone
