CB7 - control and homeostasis (Menstrual cycle, puberty)

• What causes puberty?

  Hormones - mainly testostrone in males and oestrogen in females
• What male secondary sexual characteristics develop during puberty?

  ~ Deeper voice.

  ~ Testostrone cause testes to produce sperm.

  ~ Increase in height.
• What is the menstrual cycle?

  A cycle of changes in a women's reproductive system, where the uterus lining builds up and breaks down when theres no pregnancy.
• How long does the menstrual cycle take?

  Every 28 days
• On which day does the menstrual cycle begin?

  Day 1
• What happens during Stage 1 (days 1-5) in the menstrual cycle?

  Menstruation - where the thickened part of the uterus breaks down and lost along with the unfertilised egg cell. Ready for the next cycle.
• What happens during Stage 2 (5-14)?

  After menstruation, the uterus lining starts to get thicker again.
• Why does the uterus lining needs to be thickened during the menstrual cycle?

  So that the fertilised egg can implant into the wall of the lining for growth where theres nutrients it can receive.
• What happens during Stage 3 (13-15)?

  Ovulation takes place where the egg is released from the ovary.
• What happpens during Stage 4 (15-28)?

  The uterus lining is maintained and slowly starts to thicken, ready to accept a fertilised egg. The unfertilised egg cell would travel along the oviduct to the uterus.
• What happens after stage 4 if no fertilised egg implants the uterus lining?

  The menstrual cycle repeats.
• What happens after stage 4 if a fertilised eggdoes implant into the uterus lining?

  The menstrual cycle pauses and the lining will be maintained to allow the fertilised egg cell to develop.
• Why does the fertlised egg cell implant into the uterus lining?

  The uterus lining provides a good nutrient and oxygen supply as it has good blood flow, it also provides protection for it as it gets surrounded by uterine tissue.
• Wht are the 4 hormones that control events in the menstrual cycle?

  ~ FSH

  ~ LH

  ~ Oestrogen

  ~ Progestrone
• What is FSH and what does it do?

  ~ Follicle-stimulating hormone.

  ~ Released by the pituitary gland.

  ~ Causes an egg to mature in the ovaries.

  ~ Stimulates oestrogen production.
• What is LH and what does it do?

  ~ Lutenizing hormone

  ~ Released by the pituitary gland

  ~ stimulates release of egg from ovary (ovulation occurs)
• What is progestrone and what does it do?

  ~ Released by the corpeus lateum.

  ~ Maintains the lining of the uterus.

  ~ Prevents the release of hormones that cause the egg to be released.
• What is the role of oestrogen in Stage 2?


  It stimulates the uterus lining to build up.
• What is the role of progestrone in Stage 4?

  It maintains the uterus lining after ovulation.
• How does progestrone maintain the uterus lining?

  ~ Inhibits FSH and LH.

  ~ Prevents the uterus lining shredding after fertilisation.

  ~ Allows nutrients and fluids to be secreted for the development of the fertilised egg.
• How does FSH and oestrogen interact?

  ~ When the egg matures in the follicle due to FSH, it also stimulates the release of oestrogen.

  ~ As levels of oestrogen increases, it inhibits the production FSH and works on building the uterus, ready for a fertilised egg.
• How does oestrogen and LH intereact?

  High levels of oestrogen stimulate the release of LH so the production peaks around day 14 where ovulation occurs and the egg is released into the follopian tube.
• How does levels of LH and progestrone intereact?

  As LH triggers ovulation, the follicle creates a corpus luteum where progrestrone is produced and its levels rise.
• The uterus wall is maintained untill late in the cycle when the progestrone & oestrogen levels fall resulting in menstruation (period).
• What happens to progestrone and oestrogen levelsif there is fertilisation?


  The levels remain consistant as they support the development of the embryo and maintain the uterus lining.
• How do females struggle with infertility?

  ~ The eggs may not mature properly

  ~ The eggs may not release properly
• How would males struggle with fertility?

  The sperm cannot swim well enough to reach the egg.
• What 2 hormones would be used when treating fertility?

  FSH and LH
• What 2 techniques are there to increase chances of pregnancy?

  Clomifene therapy & IVF
• What is Clomifene therapy and how does it work?

  ~ Clomine therapy is when a mother is injected with FSH and LH to increase the chances of pregnancy via sexual intercourse.

  ~ The FSH helps to stimulate the growth and maturation of the eggs while LH allows the matured eggs to be released from the ovaries into the follopian tube
• What are some side effects of Clomifene therapy?

  ~ Hormonal changes can lead to mood swings.

  ~ Increased chance of multiple pregnancies.
• What is IVF?

  In-vitro fertilisation, where the sperm and the egg are fertilised outside the womb and then planted back in.
• How does IVF work?

  1. The mother is treated with FSH and LH to mature & release eggs.

  2. Eggs are collected from the mother.

  3. Sperm is collected from the father and its used to fertilise the eggs in the labatory.

  4. Once the embryos are fertilised and form tiny balls of cells one of them are inserted into the mother's uterus.

  5. The embryos then develop the usual way.
• What are three benefits of IVF?

  ~ Provides a way for an infertile couple to have a child.

  ~ Same-sex couples and single mothers could have a child through donors, surrogacy, etc.

  ~ Eggs could be developed in a controlled environment.
• What are three issues with IVF?

  ~ Success rates are low due to complexity and potential underlying fertility issues.

  ~ Lead to multiple births as more than one embryo is inserted into the mother for increase in success rate.

  ~ Physically demanding for the mother as she has to take fertility drugs, have her eggs collected and receive embryos.
• What is the purpose of contraception?


  To prevent pregnancy
• What are 2 methods of contraception?

  Barrier method & hormonal
• What 2 hormones would be used in hormonal contraception?

  Oestrogen and progestrone
• What are 3 methods of hormonal contraception?

  ~ Contraceptive pill (with oestrogen + progestrone).

  ~ Oestrogen-only pill

  ~ Progestrone-only pill
• How does Oestrogen prevent pregnancy?

  Oestrogen inhibits the release of FSH so no eggs would be produced or matured and it also builds up the uterus lining.