July 6, 2021
In this blog post, we'll go through the menstrual cycle and birth control in I/GCSE Biology! 😆
Hormones
- Body processes controlled by chemicals (hormones)
- Produced by organs called glands
- Pass from glands into bloodstream, transports them around the body
- Target organ – the organ the hormone affects
The menstrual cycle
It is important to memorize the menstrual cycle in I/GCSE Biology!
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
Please remember this in I/GCSE Biology too!
- FSH stimulates egg to mature, Oestrogen doesn’t cause egg to release, LH stimulates egg release
- If pregnant then progesterone is made by ovaries.
- Oestrogen and progesterone continue being produced
- Progesterone helps maintain womb lining
👇 Let's look at the diagram showing the menstrual cycle below! 👇
Birth control
The contraceptive pill
- Pill to stop women from becoming pregnant
- 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)
- 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
- 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)
References:
- "Singal molecules released by endocrine cells travel through what to reach the target cells?", https://d1j63owfs0b5j3.cloudfront.net/pop-quiz/answerImage/Cellular-communication-Pop-quiz.png
- "Hormone systems - menstrual cycle - controlling fertility - use of hormones - methods of contraception - IVF fertility treatments", https://docbrown.info/ebiology/ebiopics/hormone2.gif
- "Boardworks GCSE Science: Biology Hormones", https://slideplayer.com/slide/6252695/21/images/15/How+does+the+contraceptive+pill+work.jpg
And we're done with this topic! Well Done!
Drafted by Alyssa (Biology)