Puberty And The Menstrual Cycle Flashcards
What happens to people’s hormones at puberty and what are the wider effects?
Your body starts releasing sex hormones that trigger off secondary sexual characteristics (like facial hair and breasts), and causes eggs to mature in women.
What is the main male reproductive hormone, where is it produced, and what does it do?
Testosterone.
It’s produced by the testes.
It stimulates sperm production.
What is the main female reproductive hormone, where is it produced, and what does it do?
Oestrogen.
Produced by the ovaries
Brings about physical changes and is involved in the menstrual cycle
How many stages does the Menstrual Cycle have?
Four stages
What happens in each stage of the menstrual cycle?
Stage 1- Day 1- menstruation starts. The uterus lining breaks down for about 4 days.
Stage 2- Day 4 - Day 14 -The uterus lining builds up again into a thick spongy layer full of blood vessels, ready to receive a fertilised egg.
Stage 3-Day 14- An egg develops and is released from the ovary - this is called ovulation.
Stage 4- Day 14 -28- The wall is then maintained for this period. If no fertlised egg has landed on the uterus wall by day 28, the spongy lining starts to break down and the whole cycle starts again.
What four hormones is the Menstrual Cycle controlled by?
FSH (Follicle-Stimulating hormone)
Oestrogen
LH (Luteinising hormone)
Progesterone
First hormone stage of Menstrual Cycle?
FSH
1) Produced in the pituitary gland
2) Causes an egg to mature in one of the ovaries
3) Stimulates the ovaries to produce oestrogen
What is the second stage of the Menstrual cycle?
Oestrogen
1) Produced in the ovaries
2) Causes uterus lining to grow
3) Stimulates the release of LH (which causes the release of an egg) and inhibits the release of FSH
What is the third stage of the Menstrual Cycle?
LH
1)Produced by the pituitary gland
2) Stimulates the release of an egg at day 14 (ovulation)
3)Inhibits production of oestrogen
Stimulates production of progesterone
What is the fourth stage of the Menstrual cycle?
Progesterone
1) Produced in the ovaries by the remains of the follicle after ovulation
2) Maintains the lining of the uterus during the second half of the cycle. When the level of progesterone falls, the lining breaks down.
3) Inhibits the release of LH and FSH
Diagrams for hormones and menstrual cycle
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Contraception aims to ……?
Stop the sperm reaching the ovulated egg
How can oestrogen be used as a method of contraception?
It can be used to prevent the release of an egg. If oestrogen is taken every day to keep the level of it permanently high, it inhibits the production of FSH, and after a while, egg development and production stop and stay stopped.
How can progesterone reduce fertility?
By stimulating the production of thick mucus which prevents any sperm getting through and reaching an egg.
What is The Pill and how effective is it?
It is an oral contraceptive containing oestrogen and progesterone (known as the combined oral contraceptive pill). It is over 99% effective at preventing pregnancy.
Drawbacks to The Pill
Can cause side effects like headaches and nausea and it doesn’t protect against STD’s
How does the progesterone-only pill compare to The Pill?
It has fewer side effects than the pill, and is just as effective.
How does the contrceptive patch work and how long does it last for?
It contains oestrogen and progesterone (same as the combined pill). It’s a small (5cm x 5cm) patch that’s stuck to the skin. Each patch lasts one week.
How does the contraceptive implant work and how long does it last for?
The contraceptive implant is inserted under the skin of the arm. It releases a continuous amount of progesterone, which stops the ovaries releasing eggs, makes it hard for sperm to swim to the egg, and stops any fertilised egg implanting in the uterus. An implant can last for three years.
What does the contraceptive injection contain and how long does it last for?
Progesterone
Each does lasts 2-3 months
How does the intrauterine device work and how long does it last for?
A IUD is a T-shaped device that is inserted into the uterus to kill sperm and prevent implantation of a fertlised egg.
What are the two types of IUD’s?
Plastic IUD’s that release progesterone
Copper IUD’s that prevent the sperm from surviving in the uterus
What are non-hormonal forms of contraception designed to do?
Stop the sperm from getting to the egg
Explain how condoms work
They are worn over the penis during intercourse to prevent sperm from entering the vagina. They are the only form of contraception that will protect against STD’s.
What is the diaphragm and how does it work?
It is a shallow plastic cup that fits over the cervix (the entrance to the uterus), to form a barrier. It has to be used with spermicide (a substance that disables or kills the sperm). Spermicide can be used alone as a form of contraception, but it isn’t as effective only about 70-80%.
How does sterilisation work?
It involves cutting or tying the fallopian tubes (which connect the ovaries to the uterus) in a female, or the sperm duct (tube between the testes and penis) in males. This is a permanent procedure. However, there is a very small chance that the tubes can rejoin.
How do natural methods work?
Pregnancy may be avoided by avoiding having sex whenin the mentrual cycle, the woman is most fertile. It’s not very effective.
What is abstinence?
Not having sex
What do low levels of FSH mean for fertility?
They eggs can’t mature, meaning that no eggs are released and the woman can’t get pregnant.
How do fertility drugs work?
FSH and LH can be given to women through fertility drugs to stimulate ovulation.
Pros of fertility drugs
Helps a lot of women to get pregnant
Cons of fertility drugs
Doesn’t always work, so some have to do it many times, which can be expensive.
Too many eggs could be stimulated, resulting in unexpected multiple pregnancies.
Process of IVF
1a. Before egg collection, eggs are given FSH and LH to stimulate several eggs to mature, so that more than one can be collected.
1b. Eggs are collected from the woman’s ovaries and are fertilised in a lab with sperm.
2. IVF treatment can also involve ICSI, where the sperm is injected directly into an egg, which is useful if the man has a very low sperm count.
3. The fertlised eggs are then grown into embryos in a lab incubator.
4. Once the embryos are tiny balls of cells, one or two of them are transferred to the woman’s uterus to improve the chance of pregnancy.
Pro of IVF
Can give an infertile couple a child
Cons of IVF
- Multiple births can happen, if more than one embryo grows into a foetus. This is risky for the mother and babies.
- Success rate of IVF is low, average success rate in UK is 26%. This means the process is stressful and upsetting.
- It is also physically stressful for the woman. Some women have a strong reaction to the hormones - e.g. abdominal pain, vomiting, dehydration.
What have specialised micro tools been developed for?
To use on eggs and sperm under the microscope
To remove single cells from the embryo genetic testing (check if healthy)
What is time-lapse imaging and what does it mean for IVF?
This is using a microscope and camera built into the incubator. This means that the growth of the embryos can be continuously monitored to help identify those that are more likely to result in a successful pregnancy.
Reasons why some are against IVF
- It often results in unused embryos that are eventually destroyed. Unethical because this is potential human life.
- The genetic testing of embryos before implantation raises ethical issues, as could lead to the selection of preffered characteristics, like gender or eye colour.
What is adrenaline?
A hormone released by the adrenal glands, which are just above the kidneys.
Why and how is adrenaline released? (Nervous)
It is released in response to stressful or scary situations. Your brain detects fear or stress and sends nervous impulses to the adrenal glands, which respond by secreting adrenaline.
How does adrenaline work and what effect does adrenaline have on the body?
It gets the body ready for ‘fight or flight’, by triggering mechanisms that increase the supply of oxygen and glucose to cells in the brain and muscles. For example, adrenaline increases heart rate.
How can your body control the levels of hormones (and other substances), in the blood using negative feedback systems?
When the body detects that the level of a subsance is above or below the normal level, it triggers a response to bring the level back to normal again.
What is thyroxine and what does it regulate?
A hormone released by the thyroid gland, which is in the neck. It regulates the basal metabolic rate.
What is the basal metabolic rate?
The speed at which chemical reactions in the body occur while the body is at rest.
What else is thyroxine important for?
Loads of processes in the body, like stimulating protein synthesis for growth and development.
What is thyroxine released in response to?
Thyroid stimulating hormone (TSH), which is released from the pituitary gland.
How does a negative feedback system keep the amount of thyroxine in the blood at the right level?
When the level of thyroxine in the blood is higher than normal, the secretion of TSH from the pituitary gland is inhibited (stopped). This reduces the amount of thyroxine released from the thyroid gland, so the level in the blood falls back towards normal.
To inhibit=
To stop
Blood thyroxine diagram
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