Menstrual Cycle

Question 1

What is negative feedback?

Answer 1

Has a stabilising effect because a change in levels always causes the opposite change. A rise in the levels feeds back to decrease production and reduce the level. A decrease in the levels feeds back to increase production and raise the levels.

Question 2

What is positive feedback?

Answer 2

Tends to lead to sudden rises or falls, bcos a rise causes further rises and a fall causes further falls.

Question 3

FSH function in menstruation?

Answer 3

1) Rises to a peak & stimulates the development of follicles, and stimulates secretion of oestrogen by the follicle wall.

Question 4

Oestrogen function in menstruation?

Answer 4

2) Stimulates an increase in FSH receptors in the follicles, making them more receptive to FSH, which boosts oestrogen production (POSITIVE FEEDBACK).

Question 5

Oestrogen function after menstruation?

Answer 5

3) Oestrogen stimulates repair & thickening of the endometrium (uterus lining after menstruation).
4) When it reaches high levels, oestrogen stimulates LH secretion. It also inhibits secretion of FSH by the pituitary gland, leading to a fall in oestrogen secretion.

Question 6

What does LH do?

Answer 6

5) LH rises to a sudden & sharp peak towards the end of the follicular phase. It stimulates the completion of meiosis in the egg and partial digestion of the follicle wall allowing it to burst open (ovulation).
6) LH also promotes the development of the wall of the follicle after ovulation into the corpus luteum which secretes oestrogen and progesterone.

Question 7

Role of progesterone after ovulation?

Answer 7

7) Rises in the days after ovulation, promoting the thickening and maintenance of the endometrium.