Homeostasis - Fertility And Adrenaline 139-144 Flashcards
what are the stages of the menstrual cycle
4 points
1) stage 1: menstruation starts, the uterus lining breaks down for about 4 days
2) stage 2: the lining builds up again into a thick spongy layer full of blood vessels, ready to receive a fertilised egg, from day 4-14
3) stage 3: an egg develops and is released from the ovary on day 14, called ovulation
4) stage 4: the wall is maintained for about 14 days until day 28, if there’s no fertilised egg on the wall, the lining breaks down again, repeating the cycle
what are the hormones controlled in menstruation
4 points
1) FSH (follicle-stimulating hormone)
2) oestrogen
3) LH (luteinising hormone)
4) progesterone
what does FSH do and where is it produced
3 points
1) produced in the pituitary gland
2) causes egg to mature in one of the ovaries in a structure called a follicle
3) stimulates ovaries to produce oestrogen
what does oestrogen do and where is it produced
3 points
1) produced in the ovaries
2) causes the lining of the uterus to grow
3) stimulates release of LH and inhibits release of FSH
what does LH do and where is it produced
2 points
1) produced in the pituitary gland
2) stimulates the release of an egg
what does progesterone do and where is it produced
3 points
1) produced in the ovaries by the remains of the follicle after ovulation
2) maintains the lining of the uterus during the second half of the cycle, when the level of progesterone falls the lining breaks down
3) inhibits release of LH and FSH
how can oestrogen be used to reduce fertility
2 points
1) oestrogen can be used to prevent release of an egg so can be used as a method of contraception
2) if oestrogen is taken everyday to keep its level permanently high, it inhibits the production of FSH so after a while egg development and production stop
how can progesterone be used to reduce fertility
it stimulates the production of thick mucus which prevents any sperm getting through and reaching the egg
what are some contraceptives
5 points
1) the pill
2) contraceptive patch
3) contraceptive implant
4) contraceptive injection
5) intrauterine device (IUD)
what is the pill
4 points
1) a contraceptive pill containing oestrogen and progesterone
2) it’s over 99% effective at preventing pregnancy, but has many side effects like headaches and nausea
3) doesn’t protect against STDs
4) there’s also a progesterone only pill which has less side effects and is just as effective
what is the contraceptive patch
2 points
1) a patch containing oestrogen and progesterone
2) it’s stuck onto the skin and lasts one week
what is the contraceptive implant
3 points
1) an implant inserted under the skin of the arm and releases continuous amounts of progesterone
2) this stops the ovaries releasing eggs, makes it hard for sperm to reach the egg and stops fertilised eggs implanting in the uterus
3) these can last for 3 years
what is the contraceptive injection
3 points
1) an injection containing progesterone
2) each dose lasts 2-3 weeks
what us an IUD
3 points
1) a T shaped device inserted into the uterus to kill sperm and prevent implantation of fertilised eggs
2) there are 2 types, plastic IUDs that release progesterone
3) copper IUDs that prevent sperm surviving in the uterus
what are some barrier methods of contraception and how do they work
3 points
1) condoms prevent sperm entering, there are also female condoms, these are the only form of contraception that protects from STDs
2) a diaphragm, a shallow plastic cup that fits over the cervix, needs to be used with a spermicide
3) spermicide, a substance that disables or kills sperm, only about 70-80% effective though
what are other ways to avoid pregnancy and how do they work
3 points
1) sterilisation- involves cutting or tying the fallopian tubes in a female or the sperm duct in a male, this is permanent, however there’s a very small chance the tubes and rejoin
2) ‘natural methods’- can be avoided by finding out when a woman is most fertile in her cycle, but it’s not very effective
3) abstinence- 100% effective, only way sperm definitely won’t reach the egg
how can hormones be used to increase fertility
4 points
1) some women have levels of FSH that are too low to cause the egg to mature so no egg is released and they can’t get pregnant
2) LH and FSH can be given as drugs to stimulate ovulation which helps a lot of women get pregnant
3) however it doesn’t always work so women have to do it many times which is expensive
4) too many eggs can be stimulated, resulting in twins or triplets etc.
how does IVF work
5 points
1) it involves collecting eggs from women’s ovaries and fertilising them in a lab using sperm
2) can also involve Intra-Cytoplasmic Sperm Injection (ICSI) where sperm is injected directly into an egg, useful if the man has a low sperm count
3) the fertilised eggs are grown into embryos in a lab incubator
4) when the embryos are tiny balls of cells 1 or 2 are transferred to the woman’s uterus to improve the chance of pregnancy
5) FSH and LH are given before egg collection to stimulate several eggs to mature
what are the positives and negatives to IVF
4 points
1) pro- can give an infertile couple a child
2) cons- multiple births can happen which is riskier for the mother and babies, higher risk of miscarriage and stillbirth
3) success rate is low, about 26% in the UK which makes the process stressful and upsetting
4) can be physically stressful for the woman, some have a strong reaction to the hormones - abdominal pain, vomiting, dehydration
how have advances in technology improved IVF
3 points
1) advances in microscope techniques help improve the techniques and therefore success rate of IVF
2) specialised micro tools being developed to use on eggs and sperm, also used to remove single cells from the embryo for genetic testing
3) development of time-lapse imaging means growth of embryos can be continuously monitored to help identify those that are more likely to get a result in a successful pregnancy
why are some people against IVF
2 points
1) the process often results in unused embryos that are eventually destroyed, so people think its unethical as they’re potential human lives
2) the genetic testing of embryos before implantation also raises ethical issues as some people think it can lead to selection of preferred characteristics, like gender or eye colour
what is adrenaline
3 points
1) a hormone released by the adrenal glands
2) released in response to stressful or scary situations - your brain detects fear or stress and sends nervous impulses to the adrenal glands
3) it gets your body ready for ‘fight or flight’ by triggering mechanisms that increase the supply of oxygen and glucose to cells in the brain and muscles
how can hormone release be affected
2 points
1) using negative feedback systems
2) when the body detects the level of a substance is above or below the normal level it triggers a response to make it normal again
what does thyroxine do
2 points
1) thyroxine is released the the thyroid in the neck
2) it helps regulate the metabolic rate, stimulating protein synthesis for growth and development
