5.3 - Animal and Plant Hormones

• The men's main reproductive hormone is testosterone and is produced in the testes. The women's main reproductive hormone is oestrogen and is produced in the ovaries.
• What is stage 1 of the menstrual cycle?

  When menstruation starts and the uterus lining breaks down (4 days)
• What is stage 2 of the menstrual cycle?

  The uterus lining builds up again (day 4-14) into a thick, spongy layer of blood vessels, ready to receive a fertilised egg.
• What is stage 3 of the menstrual cycle?

  The egg is released from the ovary (around day 14) called ovulation.
• What is stage 4 of the menstrual cycle?

  The wall is maintained (day 14-28) If no fertilised egg has landed by day 28, the lining starts to break down again.
• Hormonal control for menstrual cycle:

  Follicle stimulating hormone (causing eggs to mature in ovaries); luteinising hormone (stimulates release of egg); oestrogen and progesterone (growth and maintenance of lining).
• What is the hormonal interaction with the menstrual cycle?

  FSH causes egg to mature and stimulates ovaries produce oestrogen. Oestrogen causes lining of the uterus to grow. Stimulates release of LH and stops release of FSH. LH stimulates release of egg. Progesterone maintains lining of uterus, when levels falls, lining breaks down.
• If oestrogen is taken every day (levels keep permanently high)it inhibits FSH production and egg maturation. Stopping the egg release. Progesterone does the same (from egg onwards).
• Pros of contraceptive pill:

  over 99% effective, reduces risk of getting cancer.
• Cons of contraceptive pill:

  Isn't 100% effective; has bad side effects; doesn't protect against STDs
• Patches contain oestrogen and progesterone and lasts 1 week. Implant contains progesterone and lasts 3 years. Injection contains progesterone and lasts 2-3 months.
• What are the barrier methods?

  Condoms and a diaphragm
• Problems with fertility drugs (FSH & LH):

  Don't always work. Too many eggs stimulated.
• Pros and cons of IVF:

  Multiple births can happen; success rate is low; emotionally stressful.
• Thyroxine: the main hormone produced by the thyroid gland, acting to increase metabolic rate and so regulating growth and development.
• When the level of thyroxine in the blood is too high, the secretion of TSH from pituitary gland is stopped. Reducing the amount of thyroxine released from the thyroid gland and the levels fall back to normal.
• When the level of thyroxine in the blood is too low, the secretion of TSH from pituitary gland is stimulated. Increasing the amount of thyroxine released from the thyroid gland and the level rises back to normal.
• Phototropism - plant growth in response too light. Gravitropism - plant growth in response too gravity.
• 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 different stimuli.
• Extra auxin promotes growth in the shoot but inhibit growth in the roots, there can also be an unequal distribution of auxin in the shoot/root.