GCSE · Biology · Edexcel · Spec 1BI0

Hormonal contraception

Your body already has an off-switch for releasing an egg. Some contraceptives work by pressing it for you. Here's how.

Biology · Hormonal contraception

How a pill can stop an egg ever being released

This web is for an oral pill that prevents ovulation. Draw an arrow from each cause to the thing it leads to. Start at the pill's hormones, and watch for two routes that end up in the same place.

  1. The pill's hormones (oestrogen and progesterone)
  2. FSH stopped
  3. LH stopped
  4. No egg matures in the follicles
  5. No ovulation
  6. No fertilisation (outcome)
Add a link

No links yet.

Exam line: Say both routes: FSH stopped means no egg matures, LH stopped means no ovulation. Then finish the chain: no egg, so no fertilisation.

Same brakes, different trigger

A normal cyclevsA pill that prevents ovulation

Tap each row's reveal. Look at which side has the egg released.

Focus

FSH

A normal cycle

Released, and it makes a follicle mature.

A pill that prevents ovulation

Held back by the pill's hormones.

The insight

Here's the surprise: in the normal cycle, high levels of oestrogen and progesterone inhibit FSH in the same way. The pill borrows a brake your body already has.

LH

A normal cycle

Secreted once oestrogen has done its job (oestrogen causes it).

A pill that prevents ovulation

Release prevented by the contraceptive's oestrogen and progesterone.

The egg

A normal cycle

Released around day 14.

A pill that prevents ovulation

Never released.

Fertilisation

A normal cycle

There is an egg for sperm to meet.

A pill that prevents ovulation

Nothing to meet, so it can't happen.

Biology · Hormonal methods

Which method does each fact belong to?

For each fact, tick every set it belongs to. Tick both if it is true of both, and neither if it is true of neither. The overlap is the middle bit.

  • A Oral pill
  • B Injection or implant
  1. Contains or releases progesterone
  2. Can prevent ovulation
  3. Taken regularly
  4. The combined type also contains oestrogen
  5. Sickness or diarrhoea can stop it working
  6. May have side effects on weight, mood and blood pressure
  7. Releases progesterone slowly over a long time
  8. An injection lasts a number of months
  9. Protects against sexually transmitted infections

Biology · Hormonal contraception

Which idea is closest to yours?

Zara's friend says: 'Once you're on the pill, you're completely covered.'

Which is closest to what you think right now?
How sure are you?

Biology · Hormonal contraception

Write it out, then check yourself

A woman takes a combined contraceptive pill that prevents ovulation. Explain how the pill stops her becoming pregnant. [4 marks]

0 words · your answer stays on this page and is not sent anywhere.

Exam line: Each link in the chain is its own point. A good answer doesn't skip from hormones straight to no pregnancy.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

What you need to know

  • Hormones are chemical messengers made by glands, carried in the blood plasma and detected by receptors on cells of their target organs.
  • In the menstrual cycle, FSH causes a follicle to mature, oestrogen causes LH to be secreted, and LH causes ovulation, the release of an egg, around day 14.
  • Progesterone maintains the uterus lining and prevents FSH and LH from being released. High oestrogen and progesterone inhibit FSH.
  • Have a goA friend says: 'If FSH and LH were both switched off, the egg would still pop out on day 14.' Is she right?

    No. With no FSH no follicle matures, and with no LH there is no ovulation.

    FSH starts the follicle maturing and LH causes ovulation, so without both there is no mature egg and nothing to release it.

  • Contraception prevents fertilisation, the fusing of sperm and egg in the fallopian tube. Hormonal methods do it by changing normal hormone levels.
  • The oral pill is taken regularly. The combined pill contains oestrogen and progesterone, and the mini pill contains only progesterone.
  • Have a goMaya's pill packet lists oestrogen and progesterone. Which type of pill has she got?

    The combined pill.

    The combined pill contains both hormones. The mini pill contains only progesterone.

  • Some oral pills prevent ovulation: their hormones stop the secretion of FSH, so no eggs mature in the follicles.
  • Oestrogen and progesterone in contraceptives also prevent the release of LH, the hormone that causes ovulation.
  • No ovulation means no egg released, so sperm and egg cannot meet and fertilisation cannot take place.
  • Have a goPut these in the order they happen: no fertilisation, FSH and LH stopped, no ovulation.

    FSH and LH stopped, then no ovulation, then no fertilisation.

    Each step leads to the next: without FSH and LH there is no ovulation, so there is no egg for sperm to meet.

  • The injection and the implant release progesterone slowly over a long time, and prevent follicles maturing and ovulation. An injection lasts months.
  • Pills are not 100% effective: a missed or late dose, taking one after ovulation, or sickness or diarrhoea can stop the hormone changes.

The big picture

Hormones are chemical messengers. In the menstrual cycle, FSH matures a follicle and LH causes ovulation. Hormonal contraception changes the normal hormone levels. In some oral pills, the hormones stop FSH, so no eggs mature, and also stop LH, so ovulation does not take place. With no egg, sperm and egg cannot meet and fertilisation cannot happen. Hormonal pills are not 100% effective, and hormonal contraception gives no protection against sexually transmitted infections.

Key points

1FSH matures a follicle and LH causes ovulation. Contraceptive hormones stop both, so no egg matures and none is released.
2In the normal cycle, high oestrogen and progesterone inhibit FSH. Some pills reuse that same inhibition.
3No ovulation means no egg, so sperm and egg cannot meet and fertilisation cannot take place.
4The injection and implant release progesterone slowly over a long time. An injection lasts a number of months.
5Hormonal pills are not 100% effective, and hormonal contraception gives no protection against sexually transmitted infections.

Worked example

Problem

Priya's first contraceptive pill is taken the day after she ovulated. Her friend says: 'It's hormones, so it works straight away. Pills are 100% effective.' Is her friend right?

⚠ Watch out

Thinking hormonal contraception is certain to work and protects against everything. It works only while the hormone changes are maintained, and a missed or late dose, taking the pill after ovulation, or sickness or diarrhoea can stop them. It gives no protection against sexually transmitted infections.

🧠

Memory hook

FSH Starts the follicle, LH Launches the egg. The pill's hormones stop both, so nothing starts and nothing launches.

✓

Check yourself

Cover the page. Say the two routes from the pill's hormones to no fertilisation out loud, one for FSH and one for LH. Which step do they share?

Flashcards

(13)
What are hormones?
Chemical messengers made and secreted by glands, transported in the blood plasma and detected by receptors on cells of their target organs.
What does FSH do in the menstrual cycle?
It causes a follicle to mature and oestrogen to be released.
What does LH do?
It causes ovulation, the release of an egg, around day 14.
What does progesterone do in the normal cycle?
It maintains the uterus lining and prevents FSH and LH from being released.
What is fertilisation?
The fusing of sperm and egg in the fallopian tube.
What does hormonal contraception do to the menstrual cycle?
It changes the normal levels of hormones, so it disrupts the normal processes of the cycle.
Which hormones are in the combined pill and the mini pill?
The combined pill contains oestrogen and progesterone. The mini pill contains only progesterone.
How do some oral pills prevent ovulation?
Their hormones stop the secretion of FSH, so no eggs mature in the follicles and ovulation does not take place.
What else do oestrogen and progesterone in contraceptives prevent?
The release of LH, the hormone that causes ovulation.
Why does no ovulation mean no fertilisation?
No egg is released, so sperm and egg cannot meet in the fallopian tube.
How do the injection and implant work?
They release progesterone slowly over a long time, and prevent the maturation of follicles and ovulation. An injection lasts a number of months.
Name three things that can stop a hormonal pill working.
A missed or late dose, taking the pill after ovulation, and sickness or diarrhoea (the pill might not be absorbed).
What does hormonal contraception not protect against, and what might the oral pill cause?
It does not protect against sexually transmitted infections. The oral pill may cause changes in weight, mood and blood pressure.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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