Life goes on

Question 1

Four sex hormones control the female menstruation cycle:

Answer 1

• FHS (follicle stimulating hormone) stimulates an egg to develop in the ovaries.
• LH (luteinising hormone) controls ovaries ovulation (egg release).
• Progesterone maintains the uterus walls
• Oestrogen repairs the uterus walls

Question 2

Where are FSH and LH released from?

Answer 2

They are released from the pituitary glands in the brain.

Question 3

Negative feedback mechanism

Answer 3

Negative feedback mechanisms (which restore the situation after change) control the levels of sex hormones in the menstrual cycle. The cycle is triggered by the receptors in the hypothalamus.

Question 4

How does the menstrual cycle work?

Answer 4

• If fertilisation does not occur the levels of oestrogen and progesterone decrease.
• When oestrogen and progesterone levels are low,menstruation occurs
• A message is sent to the hypothalamus that hormone levels are low again. This causes the cycle to begin again.
• If an egg is fertilized, the levels of progesterone remain high and no FSH is produced, so no more eggs development and the uterus lining does not break down.

Question 5

How can fertility be controlled?

Answer 5

Fertility in humans can be controlled by the use of artificial sex hormones by controlling egg release and implantation. The contraceptive pill prevent ovulation and fertility drugs help to ensure ovulation.

Question 6

What do artificial sex hormones do?

Answer 6

Artificial sex hormone prevent ovulation by making the body think it is pregnant and this inhibits FSH release. Eggs in the ovaries are therefore not stimulated to develop.

Question 7

Methods for treating infertility:

Answer 7

• Artificial insemination, where sperm are placed into the vagina by syringe
• Using FSH to stimulate egg development
• IVF, where an egg is fertalised by sperm outside the body
• Egg donation, where an egg is donated from another female, then fertalised and placed inside the uterus.
• An ovary transplant from another female

Question 8

What does fertility treatment do?

Answer 8

All fertility treatments increase the chances of a successful fertlisation and pregnancy. This is very important for couples who feel incomplete without a family. However, not all people agree with such treatments, which are expensive for the individuals and for the NHS.

Question 9

Problems of fertility treatments?

Answer 9

• All fertility treatments raise moral issues, and have risks and benefits. In particular, egg donation, surrogacy and ovary transplants raise raise medical issues (such as rejection) as well as moral ones (for example about paternity).
• Some treatments are very expensive with a low rate of success. A single IVF treatment cycle costs about £6,000, with an average success rate of about 25% and the risk of multiple births and lower birth rates.

Question 10

A developing foetus can be checked to see if there are any abnormalities (e.g. in its growth or genetic make-up). Checking can be done by:

Answer 10

• Amniocentesis - extracting and testing cells in the amniotic fluid
• Chromosomal analysis - using a blood test to test cells for chromosome abnormalities.

Question 11

Using foetal screening techniques like this raises ethical issues:

Answer 11

• Whether it is right to interfere with natural processes and whether an unborn foetus has the right to life.
• The techniques also carry a small risk of causing the expulsion of the foetus.