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I/GCSE Biology: Controlling pregnancy

Controlling pregnancy

· biology,IGCSE,igcsse biology,gcse b1 notes,pregnancy

Do you guys still remember how we control pregnancy in I/GCSE Biology?

Hormones

  • Body processes controlled by chemicals (hormones)
  • In I/GCSE Biology, Produced by organs called glands
  • Pass from glands into bloodstream, transports them around the body
  • Target organ – the organ the hormone affects
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The menstrual cycle

  • Day 5
    • Follicle stimulating hormone (FSH) starts to be released by pituitary gland in brain
    • Hormone travels in blood o ovaries
    • Egg begins to develop
  • Day 7
    • Egg signals to ovaries as it develops
    • Ovaries start to produce oestrogen
    • Lining of the womb builds up
  • Day 15
    • Ovaries produce a lot of oestrogen – brain detects this
    • Brain stops producing FSH and produces luteinising hormone (LH)
    • LH triggers release of egg (ovulation)
  • Day 28
    • If egg not fertilised = lining of uterus is shed
    • Causes menstruation bleeding (period) lasts a few days
    • Cycle starts again
  • FSH stimulates egg to mature, Oestrogen doesn’t cause egg to release, LH stimulates egg release
  • In I/GCSE Biology, If pregnant then progesterone is made by ovaries.
  • Oestrogen and progesterone continue being produced
  • Progesterone helps maintain womb lining
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The contraceptive pill

  • Pill to stop women from becoming pregnant
  • In I/GCSE Biology, Hormones in pill have same effect on pituitary gland as oestrogen
  • Hormones stop pituitary gland making FSH = no egg will mature in ovaries

Benefits and problems

  • Large amounts of oestrogen = blood clots (block arteries)
  • In I/GCSE Biology, Two types of pill available – combined and mini pill
  • Combined – low doses of oestrogen and progesterone – increased risk of women developing blood clots
  • Mini pill – progesterone only – causes fewer side effects, must be taken punctually, less reliable than combined

Fertility drugs

  • In I/GCSE Biology, FSH levels too low = ovaries don’t release eggs – women can’t become pregnant
  • Treated by injecting FSH into blood
  • FSH – fertility drug as it stimulates ovaries to produce mature eggs
  • Treatment doesn’t always work, more than one egg can be released (twins, triplets, quadruplets)

That's all~

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