1. THE MENSTRUAL CYCLE
1.1. the monthly sequence where the body releases an egg and prepares the uterus in case the egg is fertilised
1.2. Stages
1.2.1. 1. menstruation (bleeding) starts on day 1 - the uterus lining breaks down and releases (lasts 4 days)
1.2.2. 2. the lining of the uterus is repaired into a thick layer full of blood vessels, ready for a fertilised egg to implant there (day 4 - 14)
1.2.3. 3. ovulation occurs on day 14 (an egg is released from the ovary)
1.2.4. 4. the lining is maintained for 14 days until day 28. if no fertilised egg has landed on the uterus, the layer breaks down and the cycle starts again
1.3. Oestrogen
1.3.1. stimulates growth of the uterus lining during stage 2 of the menstrual cycle
1.3.2. a high level of oestrogen increases LH
1.4. Progesterone
1.4.1. needed to maintain the uterus lining during stage 4 and stops the release of FSH and LH
1.4.2. released by the corpus luteum after ovulation
1.4.3. a low progesterone level allows FSH to increase and the cycle starts again
1.5. FSH
1.5.1. follicle-stimulating hormone - causes a follicle to mature in one of the ovaries and stimulates ovaries to produce oestrogen
1.5.2. produced in the pituitary gland
1.6. LH
1.6.1. luteinising hormone - stimulates the release of an egg on day 14 (ovulation) and stimulates the remains of the follicle to develop into a corpus luteum
1.6.2. produced in the pituitary gland
1.7. Pregnancy
1.7.1. if a fertilised egg in the uterus, the level of progesterone will stay high to maintain the lining of the uterus during pregnancy
2. CONTROLLING FERTILITY
2.1. Clomifene Therapy
2.1.1. woman who are infertile because they don't ovulate regularly or at all can take a drug called clomifene
2.1.2. this causes more FSH and LH to be released into the body which stimulates egg maturation and ovulation
2.1.3. by knowing when the woman will be ovulating, the couple can have intercourse during this period to improve the change of becoming pregnant
2.2. IVF
2.2.1. involves collecting eggs from the woman's ovaries and fertilising them ina lab using the man's sperm
2.2.2. the fertilised eggs then grow into embryos.once the embryos are tiny balls of cells, one or two of them are transferred to the woman's uterus. FSH and LH are given before egg collection to stimulate egg production
2.2.3. an example of Assisted Reproductive Technology - eggs being handled outside of the body in a lab
2.3. Hormonal methods of contraception
2.3.1. Oestrogen
2.3.1.1. can be used to prevent egg release
2.3.1.2. if oestrogen is taken every day to keep its level high, it stops FSH production and egg release stops
2.3.2. Progesterone
2.3.2.1. reduces fertility
2.3.2.2. stimulates the production of thick cervical mucus which prevents any spermgetting through to the egg
2.3.2.3. some progesterone-only contraceptives can also stop maturation and stop the release of an egg
2.3.3. Types of hormonal contraceptives
2.3.3.1. combined pill (oral)
2.3.3.2. mini-pill (progesterone-only)
2.3.3.3. contraceptive patch (thin, plastic patch that sticks to the skin that releases oestrogen and progesterone into the bloodstream
2.3.3.4. contraception injection (contains progestrone only)
2.4. Barrier methods of contraception
2.4.1. condoms - the only form of contraception that will protect against STD's
2.4.2. diaphragm - flexible, dome-shaped device that fits over the cervix
2.5. Evaluating methods of contraception
2.5.1. when used correctly, hormonal methods are more effective at preventing pregnancy than barrier methods
2.5.2. hormonal methods also mean that the couple do not have to stop and think each time they have intercourse
2.5.3. although hormonal methods can have unpleasant side-effects (headaches, acne and mood changes) and do not protect against STI's
2.5.4. barrier methods are generally free of side-effects although some people experience allergic reactions
3. HORMONES
3.1. hormones are chemical messengers that travel in the blood and activate cells in target organs
3.2. Endocrine System
3.2.1. the endocrine glands (where hormones are produced) make up the endocrine system
3.2.2. the system uses hormones to react to changes in the environment or the body
3.3. Endocrine glands
3.3.1. pituitary gland
3.3.1.1. produces hormones that regulate body conditions - act on other glands, directing them to release hormones that bring about change
3.3.2. thyroid gland
3.3.2.1. produces thyroxine - involved in regulating things like metabolism rate, heart rate and temperature
3.3.3. pancreas
3.3.3.1. produces insulin - used to regulate blood glucose level
3.3.4. adrenal glands
3.3.4.1. produce adrenaline - used to prepare the body for a 'fight or flight' response
3.3.5. ovaries
3.3.5.1. produce oestrogen - involved in menstrual cycle
3.3.6. testes
3.3.6.1. produce testosterone - controls puberty and sperm production
3.4. Comparing nerves and hormones
3.4.1. if the response is quick and acts on a very precise area, it is proably nervous
3.4.2. if the response lasts for a long time and acts in a more general way, it is proabably hormonal
4. ADRENALINE AND THYROXINE
4.1. Adrenaline
4.1.1. released by adrenal glands (above kidneys)
4.1.2. the brain detects a fear or stress and sends nervous impulses to the adrenal glands, which then produce adrenaline
4.1.3. adrenaline gets the body ready for 'fight or flight' by triggering mechanisms that increase the supply of oxygen and glucose to cells
4.2. Thyroxine
4.2.1. released by thyroid gland (in the neck)
4.2.2. Negative Feedback
4.2.2.1. when the levels of certain substances in the body go above or below normal, it triggers responses to help bring the levels back to normal
4.2.2.2. it keeps the amount of thyroxine in the blood at the right level
4.2.2.3. Decrease from normal detected
4.2.2.3.1. when the level of thyroxine is lower than normal, the hypothalamus (in brain) is stimulated to release thyrotropin, releasing TRH
4.2.2.3.2. TRH stimulates the pituitary gland to release TSH
4.2.2.3.3. TSH stimulates the tyroid gland to release thyroxine so the blood level rises
4.2.2.4. Increase from normal detected
4.2.2.4.1. when the level of thyroxine is higher than normal, the release of TRH (from the brain) is stopped
4.2.2.4.2. this reduces the production of TSH, which reduces the amount of thyroxine produced and the level falls