Endocrine Control of the Menstrual Cycle

Question 1

What hormone does the hypothalamus release and what is its action? (in relation to the menstrual cycle)

Answer 1

Gonadotropin releasing releasing hormone (GnRH). Stimulates ant. pituitary to secrete FSH + LH.

Question 2

What hormone does the pituitary release and what is its action? (in relation to the menstrual cycle)

Answer 2

FSH + LH. Stimulates ovaries to release oestrogen and progesterone.

Question 3

What is the negative feedback for this system?

Answer 3

For majority of the cycle, oestrogen and progesterone inhibit hypothalamus and ant. pituitary from releasing GnRH and FSH + LH respectively.

Question 4

What is the positive feedback for this system?

Answer 4

Between day 12-14 of a 28-day cycle, oestrogen + progesterone stimulate the hypothalamus and ant. pituitary to release GnRH and FSH + LH respectively.

Question 5

What hormone stimulates ovulation?

Answer 5

LH surge because of oestrogen.

Question 6

What are the 4 phases of the menstrual cycle

Answer 6

Follicular phase
Ovulation
Luteal phase
Menstruation

Question 7

What happens in the follicular phase?

Answer 7

FSH causes the follicle to mature and oestrogen begins to rise inhibiting the development of other follicles.

Question 8

What happens in ovulation?

Answer 8

Around day 12, the large amount of oestrogen causes a spike in LH due to positive feedback. The follicle ruptures and releases a secondary oocyte.

Question 9

What happens in the luteal phase?

Answer 9

The ruptured follicle forms a corpus luteum that secretes progesterone and some oestrogen to maintain the uterine lining.

Question 10

What happens in menstruation?

Answer 10

When the corpus luteum degenerates into a corpus albicans, there is no pregnancy and oestrogen and progesterone drop, causing menstruation.