The Menstrual Cycle

Question 1

What are the three classes of molecules involved in the Menstrual cycle?

Answer 1

Neuropeptides
Glycoproteins
Steriods

Question 2

Which neuropeptide(s) are involved in the Menstrual Cycle?

Answer 2

Gonadotropin releasing hormone (GnRH)

Question 3

Which glycoprotein(s) are involved in the Menstrual Cycle?

Answer 3

Luteinising Hormone (LH)
Follicle Stimulating Hormone (FSH)
Chorionic Gonadotropin (CG)

Question 4

Which sterioid(s) are involved in the Menstrual Cycle?

Answer 4

Progestrogens
Androgens
Oestrogens

Question 5

Describe the structure of the Glycoproteins involved in the control of the Menstrual Cycle

Answer 5

Heterodimers, with a common alpha chain and a differing beta chain

Question 6

Where is GnRH released from? And where is it released to?

Answer 6

It is released from the hypothalamus and into the portal plexus at a pulsatile, hourly rate from puberty

Question 7

How is GnRH released from the hypothalamus in a prepubescent female?

Answer 7

Irregularly

Question 8

GnRH released from the hypothalamus into the portal plexus acts on where?

Answer 8

The anterior pituitary gland’s gonadotroph cells

Question 9

Is the oocyte number fixed in females?

Answer 9

Yes, no new primordial germ cells are synthesised 3 months post conception

Question 10

Until puberty, the oocytes arrest at what stage?

Answer 10

Diplotene (Prophase 1) as primary oocytes

Question 11

The precursor of all Steroids are what? And what pathway synthesises these Steroids?

Answer 11

Cholesterol, via the common biosynthetic pathway occurring in the mitochondria

Question 12

What are the two layers of cell tissue surrounding an ovary in a follicle?

Answer 12

Theca cells

Granulosa cells

Question 13

What is a follicle?

Answer 13

A structural unit in which oocytes develop in

Question 14

The Ovarian Cycle is comprised of what two phases? How long do each last

Answer 14

The Follicular Phase (14 days)

The Luteal Phase (14 days)

Question 15

The Follicular Phase of the Ovarian Cycle begins when and is dominated by which hormone?

Answer 15

On the day of menses, and is dominated by Oestrogen

Question 16

The Luteal Phase of the Ovarian Cycle is dominated by which hormone?

Answer 16

Is dominated by Progesterone

Question 17

In the Luteal Phase what happens to the follicle? Briefly state

Answer 17

The follicle ruptures and forms a corpus luteum

Question 18

What happens in the Follicular Phase? Explore in detail

Answer 18

1. Hypothalamus gives off GnRH into the portal plexus and stimulates release of LH and FSH from the anterior pituitary gland’s gonadotroph cells
2. The cells in the follicle have receptors for LH (Theca cells) and FSH (Granulosa cells)
3. Once LH binds to Theca cells, it stimulates Androgen release
4. Once FSH binds to Granulosa cells, it stimulates Androgen Aromatase release, which converts the former Androgen to form Oestrogen which is released in the plasma
5. Oestrogen acts on the Anterior Pituitary gland and prevents further FSH and LH release (- feedback)
6. Granulosa cells also release Inhibin B which presents further FSH release
7. Androgens also act on Granulosa cells to stimulate Follicular growth
8. A dominant follicle grows, and there is a sharp rise in Oestrogen to a threshold (200 x basal level)
9. This now positively acts on the Anterior Pituitary to release LH, and Granulosa cells now express LH receptor, and LH binds to both Theca and Granulosa cells
10. This stimulates Granulosa cells to secrete Progesterone

Question 19

What causes Menopausal symptoms, such as the hot flushes, mood swings, tiredness, dry skin etc.?

Answer 19

When you run out of eggs, you run of Oestrogen

Question 20

What is the role of Anti-malarian hormone?

Answer 20

Prevents surrounding follicles from growing