Section 7 - Animal coordination, control and homeostasis - Menstrual cycle and fertility

Question 1

How long is a menstrual cycle usually?

Answer 1

28 days

Question 2

In 4 stages of menstrual cycle, what happens in stage 1? Which days? Which hormone released?

Answer 2

Menstruation starts, uterus lining breaks down and is released, days 1-4, FSH

Question 3

In 4 stages of menstrual cycle, what happens in stage 2? Which days? Which hormone released?

Answer 3

Uterus lining repaired, from day 4-14, until it becomes a thick spongy layer full of blood vessels ready for a fertilised egg to implant there, oestrogen

Question 4

In 4 stages of menstrual cycle, what happens in stage 3? Which days? Which hormone released?

Answer 4

Ovulation: an egg develops and is released from ovary at about day 14, LH

Question 5

In 4 stages of menstrual cycle, what happens in stage 4? Which days? Which hormone released?

Answer 5

Lining maintained for about 14 days, until day 28. If no fertilised egg landed on uterus wall by day 28, spongy lining starts to break down again and whole cycle starts over, progesterone

Question 6

What is FSH released by, causes, and stimulates?

Answer 6

FSH released by pituitary gland, causes follicle to mature in one of ovaries, and stimulates oestrogen production

Question 7

What is oestrogen released by, causes, and stimulates?

Answer 7

Oestrogen released by ovaries, causes uterus lining to thicken and grown, and a high level stimulates an LH surge

Question 8

What is LH released by, causes, and stimulates?

Answer 8

LH released by pituitary gland, stimulates ovulation at day 14 - egg released, and stimulates remains of follicle to develop into corpus luteum - which secretes progesterone

Question 9

What is progesterone released by, causes and inhibits?

Answer 9

Progesterone released by corpus luteum after ovulation, maintains uterus lining, and inhibits release of FSH and LH

Question 10

How does the menstrual cycle start again?

Answer 10

When level of progesterone falls and low oestrogen level, uterus lining breaks down. Low progesterone level allows FSH to increase and then whole cycle starts again

Question 11

What happens to progesterone level if a fertilised egg implants the egg?

Answer 11

Level of progesterone will stay high to maintain uterus lining during pregnancy

Question 12

Two examples of treating infertility?

Answer 12

Clomifene therapy and IVF (in vitro fertilisation)

Question 13

What is clomifene therapy?

Answer 13

Infertile women take drug called clomifene. It causes more FSH and LH to be released by body, which stimulates egg maturation and ovulation. By knowing when woman will be ovulating, couple can have intercourse during this time period to improve chance of pregnancy

Question 14

What is IVF (in vitro fertilisation)?

Answer 14

Involves collecting eggs from woman’s ovaries and fertilising them in lab using man’s sperm, which then grown into embryos. Once embryos are tiny balls of cells, one or two transferred to woman’s uterus to improve chance of pregnancy. FSH and lH given before egg collection to stimulate egg production

Question 15

2 hormones used as contraceptives and how they work to prevent pregnancy?

Answer 15

Oestrogen - inhibits production of FSH to stop egg maturing
Progesterone - Stimulating production of thick cervical mucus, which prevents sperm getting through uterus entrance and reaching egg, inhibits FSH and LH so stops egg maturing and releasing

Question 16

2 examples of barrier methods of contraception and how they prevent pregnancy?

Answer 16

Condoms and diaphragms which put barrier between sperm and egg so they don’t meet

Question 17

2 pros of using hormonal methods of contraception?

Answer 17

More effective at preventing pregnancy than barrier methods

Using hormonal methods mean couple don’t have to stop and think about contraception each time for intercourse

Question 18

2 cons of using hormonal methods of contraception?

Answer 18

Unpleasant side-effects such as headaches, acne and mood changes.
Don’t protect against STIs which condoms do.