Hormones in human reproduction + Contraception + Infertility + Feedback Ssystems

What happens during puberty?

Reproductive hormones cause secondary sex characteristics to develop.

What is the main female reproductive hormone?

Oestrogen.

What is the main male reproductive hormone?

Testosterone.

How many stages are in the menstrual cycle?

4.

What happens in the first stage of the menstrual cycle?

Menstruation starts and the uterus lining breaks down for about 4 days.

What happens in the second stage of the menstrual cycle?

The uterus lining builds up again from days 4-14, into a thick spongey layer full of blood vessels, ready to recieve a fertilised egg.

What happens in the third stage of the menstrual cycle?

Ovulation; an egg develops and is released from the ovary at day 14.

What happens in the fourth stage of the menstrual cycle?

The wall is maintained for about 14 days until day 28. If no fertilised egg had landed on the uterus wall by day 28, the spongey lining starts to break down and the whole cycle starts again.

What are the four hormones the menstrual cycle is controlled by?

• FSH (Follicle-Stimulating hormone).

• Oestrogen.

• LH (Luteinising hormone).

• Progesterone.

What is FSH?

• Produced inthe pituitary gland.

• Causes an egg to mature in one of the ovaries.

• Stimulates the ovaries to produce oestrogen.

What is oestrogen?

• Produced in the ovaries.

• Causes the lining of the uterus to grow.

• Stimulates the release of LH.

• Inhibits the release of FSH.

What is LH?

• Produced by the pituitary gland.

• Stimulates the release of an egg on day 14 (ovulation).

What is progesterone?

• Produced in the ovaries by the remains of the follicle after ovulation.

• Maintains the lining of the uterus during the second half of the cycle. - When the level of progesterone falls, the lining breaks down.

• Inhibits the release of LH and FSH.

What is contraception?

Trying to stop/prevent pregnancy.

WHat are the two types of contraception that can be used to control fertility?

Hormonal and non-hormonal.

What two hormones are involved in controlling fertillity?

Oestrogen and progesterone.

How can oestrogen control fertility?

It can prevent the release of an egg; if its taken every day and its levels in the body are permanently high, it inhibits FSH production and after a while egg development and production stop.

How can progesterone control fertility?

It stimlates the productionof thick mucus which prevents any sperm getting through and reaching an egg.

How do oral contraceptives work?

They contain hormones (progesterone and oetrogen) to inhibit FSH production so that no eggs mature.

How do injection, implant and skin patches work?

They slowly release progesterone to inhibit the maturation and release of eggs for a number of months or years.

How do barrier methods such as condoms and diaphragms work?

They prevent the sperm reaching an egg.

How do intrauterine devices work?

They prevent the implantation of an embryo or release a hormone.

How do spermicidal agents woek?

They kill or disable sperm.

How do surgical methods work?

Through male and female sterilisation.

What hormones are involved in increasing fertility?

FSH and LH.

How does FSH increase fertility?

Some women have levels of FSH that are too low for their eggs to mature - no egs are released and the women can’t get pregnant.

How does LH increase fertility?

Stimulates ovulation.

What are the cons of using hormones to increase fertility?

• It dosen’t always work - some women have to to it a lot of times.

• This can be expensive.

• Too many eggs can be stimulated, resulting in unexpected multiple pregnancies.

What does IVF stand for?

In Vitro Fertilisation.

How does IVF work?

• IVF involves giving a mother FSH and LH to stimulate the maturation of several eggs.

• The eggs are collected from the mother and fertilised by sperm from the father in the laboratory.

• The fertilised eggs develop into embryos.

• At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother's uterus (womb).

What are the cons to IVF?

• Multiple births can happen if more than one embryo grows into a baby which is risky for both the mother and the babies.

• The success rate of IVF is low.

• The process can be extremely stressful and upseting.

• It can be physically stressful as some women hage a strong reaction to the hormones - abdominal pain + vomitting.

Why are some people against IVF?

• The process of IVF often results in unused embryos that are eventually destroyed - some people think it is unethical.

• The genetic testing of embryos before implantaion raises ethical issues as some think that it could lead to the selection of preferred characteristics.

What is the role of adrenaline in the body?

Adrenaline is produced by the adrenal glands in times of fear or stress. It increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for ‘flight or fight’.

What is the role of thyroxine in the bpdy?

Thyroxine from the thyroid gland stimulates the basal metabolic rate. It plays an important role in growth and development.

What are thyroxine levels developed by?

Negative feedback.