Topic 5 - Homestasis and Response Flashcards
What is auxin and where is it found?
Auxin is a plant hormone found in the tips of roots and shoots. It controls the growth of plants in response to light and gravity. If auxin is only on one side of a shoot or root, it will cause it to elongate fast and turn.
How does auxin work in a shoot?
When a shoot is exposed to light more auxin accumulates on the shaded side. This makes the plant grow faster on the shaded side so the shoot bends toward the light.
If the shoot is growing sideways. Gravity will push auxin down which will stimulate growth to point the shoot upwards out the ground.
How does auxin work in the root?
When a root is growing sideways, gravity means more auxin accumulates in the lower side, this will inhibit growth and chase the tip to bend down as the upper part grows faster.
What are some commercial uses of auxin?
Weed killers - auxin disrupts normal growth patterns which kills the plant.
Growing cuttings - means cuttings rapidly produce roots
Growing cells in tissue culture - tissue culture grows clones of a plant and auxin will be added to stimulate cell division.
What is Gibberellin?
Gibberellin is a plant hormone that stimulates seed germination, stem growth and flowering.
How is gibberellin used commercially?
Controlling dormancy - by stimulating germination seeds can germinate out of season when normally the conditions are not met
Inducing flowering - some plants require certain conditions to flower, gibberellin means the they can flower anyway.
Growing larger fruit - fruit can grow large no matter there type or season.
What is ethene as a plant hormone?
A gas produced by aging plants. It causes plants to ripen.
How is ethene used commercially?
Speed up ripening - either on the plant or during transport meaning a fruit can be picked while unripe to avoid damage.
What is the ‘male’ hormone and its function?
Testosterone- produced in testes - triggers secondary sec characteristics and stimulates spermicide production
What is the ‘female’ hormone and its function?
Oestrogen - made in ovaries - triggers secondary sex characteristics and is involved in menstrual cycle
What four hormones are involved in the menstrual cycle?
FSH
LH
Oestrogen
Progesterone
What is the menstrual cycle?
A sequence of events that happens about every 28days.
When does the menstrual cycle start?
During puberty when eggs are matured
What does FSH do?
Produced in pituitary gland
Causes eggs to mature
Stimulates ovaries to produce oestrogen
What does oestrogen do?
Produced in the ovaries
Causes the uterus lining to grow
Stimulates the release of LH and inhibits FSH
What does LH do?
Produced in pituitary gland
Stimulates release of an egg
What does progesterone do?
Produced by ovaries
Maintains the uterus lining
Inhibits the release of LH and FSH
Outline the 4 stages of the menstrual cycle.
Stage 1 - menstruation starts
Stage 2 - uterus lining builds up
Stage 3 - egg develops and releases
Stage 4 - uterus wall is maintained
What is a detailed description of stage 1 of the menstrual cycle?
The uterus lining breaks down for four days
What is a detailed description of stage 2 of the menstrual cycle?
From day 4 to 14 FSH matures an egg and stimulates oestrogen to build the uterus lining back up
What is a detailed description of stage 3 of the menstrual cycle?
At around day 14 oestrogen inhibits the release of FSH an stimulates the release of LH which releases the egg
What is a detailed description of stage 4 of the menstrual cycle?q
From around day 14 to 28 the uterus lining is maintained by progesterone, if the egg isn’t fertilised by day 28 progesterone levels fall and the process begins again
What are the two types of contraception?
Hormonal and non- normal methods
Describe some non-hormonal methods of contraception.
No hormonal methods or barrier methods stop sperm reaching the egg.
- condoms cover the penis to prevent sperm entering the vagina - only form of contraceptive that protects against stis
- diaphragm fits over the cervix and is covered with spermicide
- Spermicide can be used alone but it isn’t effective
Describe hormonal methods of contraception.
- the pill contains oestrogen and progesterone - stops egg maturing and creates thick mucus to prevent egg reaching uterus
- patch - contains oestrogen and progesterone - lasts for 1 week
- implant - lasts for three years. Contains progesterone
- iud - copper kill sperm and progesterone
What hormones are used in normal contraceptives?
Oestrogen - if taken daily stops eggs maturing
Progesterone - stimulates thick mucus production that prevents sperm reaching the egg
What hormones are used to increase fertility?
FSH and LH can be given to stimulate ovulation.
What could be the reason women can’t get pregnant?
Low FSH levels - no eggs maturing - no eggs released
What does IVF stand for?
In Vitro Fertilisation
What is homeostasis?
The regulation of internal conditions to maintain optimum conditions for enzyme action and cell function.
