2. Hormonal control of reproduction Hormones control the onset of puberty, sperm production and the menstrual cycle. Which hormones cause the onset of puberty? How do they exert their control? Which hormone controls sperm production? What other hormones are involved in sperm production? Which hormones control the menstrual cycle?

At Puberty Puberty is when sperm are produced and menstrual cycle commences. Hypothalamus secretes a releaser hormone which affects pituitary gland Pituitary gland produces follicle stimulating hormone (FSH) Interstitial cell-stimulating hormone (ICSH)(male) Luteinising hormone (LH)(female) ISCH and LH are same hormone but have different effects

Male hormonal affects FSH stimulates sperm production in seminiferous tubules ICSH stimulates interstitial cells to produce testosterone Testosterone activates the prostate gland and seminal vesicles System self regulates. As testosterone levels rise they affect the pituitary gland High levels will inhibit FSH and ISCH production This is called negative feedback

Female hormone affects FSH stimulates development of follicles and ovary tissues to secrete oestrogen LH triggers ovulation, stimulates development of corpus luteum and progesterone production from corpus luteum Oestrogen stimulates endometrium (uterus lining) to develop, makes cervical mucus easier to penetrate by sperm and stimulates pituitary gland to secrete LH Progesterone stimulates further endometrial development (blood vessels) for implantation of blastocyst and inhibits secretion of FSH and LH by pituitary gland

Menstrual cycle Approximately 28 days but varies 2 phases follicular and luteal You will summarise these 2 phases from the diagrams provided

OESTROGEN PROGESTERONE

Oestrogen

Follicular phase FSH stimulates follicle development and release of oestrogen from ovary tissues Oestrogen causes release of LH and FSH LH cause ovulation at about day 14 Egg can be fertilised in next 3-4 days

Luteal phase Following ovulation LH stimulates follicle to become corpus luteum Corpus luteum secretes progesterone (and oestrogen) Progesterone stimulates endometrium development Progesterone and oestrogen levels inhibit pituitary gland so FSH and LH levels fall No new follicles develop at this stage This is an example of negative feedback No fertilisation – corpus luteum degenerates (about day 22) No progesterone and oestrogen produced About day 28 low hormone levels mean endometrium is not maintained and comes away (with a little blood) Menstruation begins

What do you know now? Hormones control the onset of puberty, sperm production and the menstrual cycle. Which hormones cause the onset of puberty? How do they exert their control? Which hormone controls sperm production? What other hormones are involved in sperm production? Which hormones control the menstrual cycle?