D3.1 - menstrual cycle (5h)

Question 1

what 2 cycles makes up the menstrual cycle?

Answer 1

• uterine cycle
• ovarian cycle

Question 2

what are the events in the ovarian cycle?

Answer 2

1. constant development of early-stage follicles.
2. selection of a follicle, containing a maturing oocyte (egg)
   - stimulated by a lack of progesterone and the presence of FSH
3. ovulation - release of the egg from the ovary to the oviduct
   - stimulated by LH
4. empty outer ring of follicle cells becomes corpeus luteum and releases progesterone
5. corpeus luteum degrades after 10-12 days

Question 3

what are events in the uterine cycle?

Answer 3

1. menstruation - loss of the endometrium (uterus lining)
   - lack of progesterone
2. repair and development of the endometrium (uterus lining)
   - stimulated by oestradiol
3. thickening of the endometrium
   - stimulated by progesterone
4. maintenance of the endometrium
   - stimulated by progesterone

Question 4

what is the corpeus luteum?

Answer 4

temporary collection of cells that forms on your ovary each menstrual cycle if you’re still getting a menstrual cycle
- it appears right after ovulation and ensure your uterus is a healthy place for a fetus to grow.

Question 5

what is the role of LH?

Answer 5

luteinizing hormone
- LH peaks trigger ovulation; the oocyte is released from the follicle
- LH triggers development of the corpeus luteum, which secretes progesterone

Question 6

what is the role of FSH?

Answer 6

follicle stimulating hormone
- stimulates development of the follicles in the ovary (egg maturation)
- follicle cell division produces oocytes
- follicles release oestradiol

Question 7

what is the role of progesterone?

Answer 7

stimulates thickening and maintenance of the endometrium (preparing for implantation)

Question 8

what is the role of oestradiol?

Answer 8

• stimulates repair and development of the endometrium.
• stimulates production of more FSH receptors on follicle cells, so they responds more strongly to FSH.

Question 9

what hormones are produced in the pituitary gland?
which hormones act on the ovaries?

Answer 9

FSH and LH

Question 10

what hormones are produced in the ovaries?
which hormones act on the uterus?

Answer 10

Oestradiol and Progesterone

Question 11

what is a negative feedback cycle?

Answer 11

a negative feedback cycle is a response that prevents the system from fluctuating outside of a set range

Question 12

what is a positive feedback cycle?

Answer 12

a positive feedback cycle is a process that amplifies a response

Question 13

what is the relationship with LH and oestradiol?

Answer 13

negative feedback cycle - LH inhibits follicle cell development and oestradiol secretion

Question 14

what is the relationship between progesterone and FSH / LH?

Answer 14

negative feedback cycle
- progesterone causes the pituitary gland to inhibit secretion of FSH and LH.

Question 15

what is the relationship between high concentrations of oestradiol and LH / FSH?

Answer 15

negative feedback cycle
high oestradiol concentrations:
- stimulates LH production
- inhibits FSH secretion

Question 16

what is the relationship between oestradiol and FSH?

Answer 16

positive feedback cycle
- increase in FSH receptors stimulates follicle development and more oestradiol is released

Question 17

what is the relationship between low concentrations of oestradiol and FSH?

Answer 17

positive feedback cycle
- low oestradiol concentration stimulates FSH production

Question 18

what is the relationship between FSH and oestradiol?

Answer 18

indirect positive feedback
- FSH stimulates oestradiol secretion

Question 19

what occurs to hormones if the egg is fertilized and you are pregnant?

Answer 19

progesterone is continually being releases, which inhibits FSH and LH.

Question 20

what does the falling levels of progesterone at the end of the cycle trigger?

Answer 20

menstruation - FSH production to restart (due to a lack of inhibition by progesterone)

Question 21

how does LH affect the corpeus luteum?

Answer 21

triggers development of the corpeus luteum, which secretes progesterone

Question 22

which menstrual hormones are involved in a positive feedback cycle?

Answer 22

• FSH and oestradiol (indirect)
• Oestradiol and FSH ( low concetrations)
• Oestradiol and FSH receptors

Question 23

which menstrual hormones are involved in a negative feedback cycle?

Answer 23

• LH and Oestradiol
• Progesterone and FSH/LH
• Oestradiol and FSH (inhibition) and LH (secretion) at high concentrations

Question 24

what is IVF?

Answer 24

In Vitro Fertilisation - where sperm and egg cells are collected and fertilised in the lab, and the resulting embryo is implanted into the uterus.

Question 25

what is the role of drugs and hormones in IVF?

Answer 25

drugs are used to suspend the normal secretion of hormones, followed by the use of artificial doses of hormones to induce super ovulation and establish a pregnancy

Question 26

what hormones would be needed to induce superovulation and why?

Answer 26

FSH to stimulate maturation of several eggs in 1 cycle, and LH to stimulate ovulation and the formation of the corpeus luteus

Question 27

what is superovulation?

Answer 27

when multiple eggs mature at once

Question 28

which hormones would be needed to establish pregnancy and why?

Answer 28

Progesterone to: - thicken and maintain the endometrium (uterus lining), ready for implantation - prevent menstruation