Homeostasis and response Pt2 Flashcards
What are the main reproductive hormones in men and women?
men - testosterone
women - oestrogen
What are the 4 stages of the menstrual cycle?
- Day 1, menstruation starts. The uterus lining breaks down for about 4 days
- From day 4 to 14 the uterus lining starts to build up again ready to receive a fertilised egg
- Day 14, ovulation happens, an egg develops and is released from the ovary
- The wall is maintained until day 28, if no fertilised egg has landed on the uterus wall by then, the cycle starts again
What is the function of FSH?
- produced in the pituitary gland
- causes an egg to mature in one of the ovaries
- stimulates the ovaries to produce oestrogen
What is the function of oestrogen?
- produced in the ovaries
- causes the lining of the uterus to grow
- stimulates the release of LH and inhibits (prevents) release of FSH
What is the function of LH?
- produced in pituitary gland
- stimulates the release of an egg at day 14
What is the function of progesterone?
- produced in the ovaries
- maintains the lining of the uterus during the second half of the cycle, when the level of the hormone falls, the lining breaks down
- inhibits the release of LH and FSH
How can hormones be used to reduce fertility?
the pill - contains oestrogen (which prevents the release of an egg) and progesterone (reduces fertility by stimulating the production of thick mucus, preventing any sperm getting through and reaching an egg).
its over 99% effective at preventing pregnancy, but can cause side effects like headaches and nausea
the contraceptive injection - also contains progesterone, each dose lasts 2-3 months
progesterone only pill - with fewer side effects than the pill and is just as effective
the contraceptive implant - inserted under the skin of the arm, can last for 3 years
What are barrier contraception’s and some examples?
They stop the sperm from getting to the egg
condoms - are worn over the penis to prevent the sperm entering the vagina during intercourse, they prevent STDs
a diaphragm - a plastic cup that fits over the cervix to form a barrier, it has to be used with spermicides that kill or disable sperm
What are other ways to avoid pregnancy?
sterilisation - involves cutting or typing the fallopian tubes in a female or the sperm duct in the male, this is permanent however there is a small chance these tubes can rejoin
abstinence - the only way to be completely sure the sperm and egg don’t meet is by not having intercourse
how can hormones be used to increase fertility?
- some women have levels of FSH that are too low to cause their eggs to mature so they cant be released and cant get pregnant
- the hormone FSH and LH can be given to women in a fertility drug to stimulate ovulation
What are the pros and cons of increasing fertility?
pros
- it helps women get pregnant
cons
- it doesn’t always work, some have to do it many times which can be expensive
- too many eggs can become stimulated, resulting in multiple pregnancies
What are the steps for IVF?
- FSH and LH are given to the woman to stimulate several eggs to mature
- the eggs are collected from the woman’s ovaries
- sperm is injected into an egg in a laboratory
- the fertilised eggs are grown into embryos in a laboratory incubator
- once the embryos are tiny balls of cells, one or two are placed into a woman’s uterus to increase the chance of pregnancy
What are the pros and cons of IVF?
pros
- fertility treatment can give a unfertile couple a child
cons
- multiple births can happen, this is risky for the mother and babies
- the success rate of IVF is low, making the process stressful and upsetting if it fails
- can also be physically stressful because some women have strong reactions to the hormones like abdominal pain, vomiting and dehydration
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Why are some people against IVF?
the process of IVF often results in unused embryos that are eventually destroyed, so some people thing think its unethical because each embryo is a potential human life
What is auxin?
a plant hormone that controls growth near the tips of shoots and roots
- it controls the growth of the plant in response to light (phototropism) and gravity (gravitropism)
- auxin is produced in the tips and moves backwards to stimulate growth
- extra auxin promotes growth in shoots but inhibits growth in roots
how do shoots grow towards light?
- when a shoot is exposed to light, more auxin accumulate on the side that’s in the shade
- this makes the cells grow faster on the shaded side so the shoot bends toward the light
Why do shoots grow away from gravity and roots grow toward gravity?
- when a shoot is growing sideways, gravity produces an unequal amount of auxin on the lower side
- this causes the lower side to grow faster, bending the shoot upwards
- a root growing sideways will have more auxin on its lower side
- but extra auxins in the roots inhibit growth so the cells on the top will grow faster and case the root to bend downwards
how can you investigate plant growth responses?
- put 10 cress seeds into 3 different petri dishes, each lined moist filter paper and label them A, B, C
- shine a light onto one of the dishes from above and two of the dishes in different directions
- leave the cress seeds for one week so you can observe their responses, and they should be growing towards the light
What are the control variables for investigating plant growth?
number of seeds - use the same number in each dish
light intensity - keep the distance between the bulb and the dish the same
water - use a measuring cylinder to add the same amount of water
type of seed - make sure they came from the same packet
