hormonal control of reproduction

Question 1

hormones

Answer 1

chemical messengers produced by endocrine glands. theyre secreted into the bloodstream. when they reach a target organ, they bring about a specific effect. in reproduction, hormones control the onset of puberty, sperm production and the menstrual cycle

Question 2

the onset of puberty

Answer 2

triggered when the hypothalamus secretes a releaser hormone whose target is the pituitary gland. this stimulates the pituitary into releasing two hormones

Question 3

hormones released by the pituitary gland

Answer 3

the first isfollicle stimulating hormone (fsh)
in females, the second is lh
in males, the second is icsh

Question 4

hormonal control of sperm production

Answer 4

fsh promotes sperm production in the seminiferous tubules
icsh stimulates the interstitial cells to produce testosterone

Question 5

testosterone

Answer 5

stimulates sperm production and activates seminal vesicles and prostate glands to produce their secretions

Question 6

negative feedback control - testosterone in the bloodstream

Answer 6

as testosterone concentration builds up in the blood stream, it reaches a level that inhibits the production which leads to a decrease in testosterone levels. this decrease causes the pituitary to release fsh and icsh

Question 7

the menstrual cycle

Answer 7

takes approx 28 days. the first day of menstruation (bleeding) is regarded as day one. it takes place in two phases, the follicular phase and the luteal phase

Question 8

the follicular phase

Answer 8

first half of the menstrual cycle, day 1-14

Question 9

role of fsh in follicular phase

Answer 9

produced by the pituitary gland it has two effects
stimulates the development and maturation of a follicle in the ovary
stimulates the wall of follicle and the ovarian tissue to secrete the hormone oestrogen

Question 10

oestrogen in the follicular phase

Answer 10

stimulates proliferation of the uterine lining (endometrium) in order to repair it following menstruation and prepares it to receive an embryo during implantation. over the 2 weeks, the levels of oestrogen in the body builds up

Question 11

high oestrogen level

Answer 11

when oestrogen levels peak, this stops the pituitary producing fsh and stimulates it to produce a surge in the secretion of lh. also causes the cervical mucus to become more water and more easily penetrated by sperm, leading to an increased chance of fertilisation

Question 12

ovulation

Answer 12

the lh surge, caused by the pituitary gland, is the direct cause of ovulation. this occurs around the midpoint of the menstrual cycle. the lh causes the wall of the follicle in the ovary to rupture and the egg is released into the oviduct and moves slowly along it, over the course of 3/4 days fertilisation may occur if the egg meets sperm

Question 13

luteal phase

Answer 13

following ovulation, lh causes the follicle to change into the corpus luteum, this secretes progesterone. progesterone and oestrogen cause the continued proliferation and vascularisation of the endometrium. over the next 10 days, the progesterone concentration inhibits to production of fsh and lh from the pituitary

Question 14

negative feedback - fsh and lh

Answer 14

combined high levels of oestrogen and progesterone prevent further follicles from developing and inhibits the production of lh and fsh by the pituitary. if fertilisation doesnt occur, the lack of lh will cause the corpus luteum to degenerate and cease producing progesterone. the sudden drop in progesterone and oestrogen causes menstruation to occur