Unit 5 - A2 - a question of timing

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Use your knowledge and apply it to the following areas... examine how the knowledge of the oestrus cycle in mammals has allowed control methods to be developed. Look at hormone based contraception (properly this time), assisted fertility, synchronising oestrus in farm animals 500-1000 words with bibliography and quotes were appropriate. Try to discuss benefits as well as the cons in some cases.

Posted: 07-02-10 20:09 by Mike McNicholas

Okay I don't exactly understand the question soooo I'm going to have a go at comparing contraceptives :]

Somebody really needs to help me go over all the hormone and feedback stuff, I'm RUBBISH at it, which is a bit of a poor cop considering I am female. *sigh*. But anyway, onward!

1. The Pill!

One of the most commonly used forms of contraception would be the oral contraceptive pill. When taken correcty, the pill has a 99% annual effectiveness. The combined contraceptive pill contains artificial versions of hormones. They have the same effect on the body as oestrogen and progesterone. (Most oral contraceptives contain a synthetic version of oestrogen, called ethinylestradiol, plus a synthetic version of progesterone, known as a progestogen.) The pill interferes with the cycle to prevent pregnancy. It works by preventing ovaries from releasing an egg, thickening the mucus at the cervix (which makes it more difficult for sperm to enter the womb and fertilise the egg), and also by making the lining of the womb unsuitable for a fertilised egg to implant on. The pill is used by millions of women worldwide, and there are many benefits such as a reduced risk of ectopic pregnancies, protection against pelvic infection, lighter and less painful periods, reduced PMS, reduced risk of certain cancers such as ovarian or endometrial, and it can also be used to treat acne. However as well as these benefits, there are some disadvantages. People with a family history of blood clots, stroke or heart disease would need to consult their GP before taking the pill due to the high risk of complications. Some people are also under the impression that the pill protects against sexually transmitted diseases, which it most certainly does not. The only protection against STI's would be condoms. There can also be side effects from the pill. For most women they are minor, and can be avoided by changing to another brand. Common side-effects are bloating, breast tenderness, headaches, acne, and mood changes. The pill also increases your risk of getting a blood clot in the legs, known as deep vein thrombosis (DVT), which can be dangerous.

2. The Patch!

This adhesive patch is worn for 3 out of every 4 weeks. If it is used correctly it is as effective as the combined oral contraceptive. It is, however, less effective in overweight women. There can be many side effects to the patch such as fluid retention or raised blood pressure, mood changes, nausea, headache, breast tenderness and abdominal pain.

3. The Progestogen Only Pill (P.O.P)!

This is used by many women who wish to avoid oestrogen. Sometimes refered to as "the mini-pill", the P.O.P again has a 99% annual effectiveness. There are many side effects to the P.O.P such as irregular periods, a risk of ectopic pregnancy if pregnancy did occur, spots, tender breasts, a small risk of ovarian cysts developing, depression and weight-gain.

4. Injection!

A single injection of medroxyprogesterone (a progestogen) can provide contraception for up to three months. It is as reliable as the pill but fertility can take a longer time to return, even if the injection is not given again. However, the menstrual cycle can be unpredictable. Periods may be irregular or heavier than usual. Fortunately this can settle down to light and infrequent periods or even none at all. It has a greater than 99% annual effectiveness. The injection can be beneficial because it can reduce the risk of ovarian cysts and ectopic pregnancies. The side-effects can include heavy, prolonged, irregular periods, headaches, and weight-gain.

5. Implant!

Progestogen implants are small, narrow, flexible rods. The rod is inserted under the skin of your upper arm. It releases a constant amount of progestogen, giving contraception for up to three years. However, the effects reverse soon after the implant is removed. It is more than 99 percent effective over a year. Implants are beneficial because they are long-lasting and reversible. Implants also make periods lighter and less frequent. They do NOT provide protection against STI's. At first there may also be some side-effects such as headaches, breast tenderness, mood changes, nausea, and unpredictable vaginal bleeding.

6. Emergency Hormonal Contraception (EHC)!

EHC is a one tablet treatment which contains levonorgestrel (a type of progestogen). It is often called "the morning after pill" but it actually works up to 72 hours after unprotected sex. Emergency contraception prevents fertilised eggs from implanting into the wall of the uterus, preventing pregnancy.

Umnn so yeah.

Posted: 08-02-10 18:55 by Lauren Carry

Hormonal contraceptives in humans

There are many different variants of hormonal birth control, these include the oral contraceptive pill, which can either contain one time of inhibitory hormone of a combination, the contraceptive implant which works on the basis of releasing a chemical etonorgestrol into your blood steam which reaches your ovaries and prevents an egg from being released and the final and most recent form of hormonal contraception is the patch which works on the principle of releasing more hormones to counteract the development of an egg.
All of these hormonal contraceptives work on the concept of following the negative feedback loops. What would normally occur during a regular menstrual cycle is providing there isn't a fertilised egg to begin ovulation then the negative feed back loop will be followed. The hormonal contraceptives work in exactly the same way. By increasing oestrogen this will inhibit the follicle stimulating hormone which will keep the stimulating hormone at a low level and ensure that no follicles will develop. This is the single version of the pill which may be just effective in some women as the combine pill. The combined pill works by increasing the levels of progesterone which inhibits the production of the luteinising hormone. This inhibition causes the maintenance of the uterus wall to be ineffective and instead of building up a wall for a potential egg to be ovulated the wall will just break down because the levels of progesterone are that high that the LH isn't effective as it is being inhibited. Both the pills are example of competitive inhibition. The competitive inhibition occurs for the hormone receptor binding sites. A hormone receptor is a receptor on the surface of a cell or in its interior that binds to a specific hormone. The hormone causes many changes to take place in the cell.

Binding of hormones to hormone receptors often trigger the start of a biophysical signal that can lead to further biological functioning, in this case it is the prevention of ovulation.

Why use or not use the hormonal contraceptives?

The main significant reason for using this form of contraceptive is to ensure a female does not end up in a pregnancy. For some people this can be a benefit, people can still have the pleasure of sex with out having the responsibility of a pregnancy afterwards. Another reason for taking the contraceptives is that a couple may not be able to bring up a child, i.e financial circumstances, or other socio-economic factors such as their society may look down upon them for deciding to have a child. In extreme cases the hormonal contraceptive can be just at useful as adrenaline to a heart attack patient, in an extreme case of the **** of a female then the woman would not want to endure the pain of a pregnancy to a male who had violated her and the contraceptive would work by not allowing a fertilised egg to begin ovulation.

The main reason for not using contraceptives are ethical religious beliefs. Some religions, in particular Christianity are pro-life and see the use of a contraceptive as a form of murder as a female is not letting the chance for a new life to be born. Christians believe that life begins at fertilisation and that the destruction of any new life is considered unethical and unjust. They believe in the Sanctity of God, this is the belief that only God has the divine right to give life or take it away and by terminating of a potential pregnancy then this is the destruction of life. The other reason for not using the hormonal contraceptive is that it doesn't protect you like a physical barrier would from contracting sexual transmitted diseases or infections such as HIV of AIDS, instead they would rather use a physical barrier to prevent this rather than using an oral contraceptive and letting an unknown STI or STD cause the potential of infertility.

The estrous cycle in mammals
Estrous cycles start in mammals after puberty in sexually mature females. Typically estrous cycles continue until death. It is the same principle of menstruation in human females. There are some similarities in animals and humans and some differences. Animals and humans have the same reproductive system and hypothalamic systems that regulate the release of hormones such as luteinising hormone (LH) and follicle stimulating hormone (FSH). So if the menstrual cycle in humans can be controlled in humans by hormonal contraception then the estrous cycle can be controlled in animals.
What's the use of controlling the estrous cycle in animals?
The main benefit in this current economic crisis is that money can be saved from not allowing animals to reproduce and provide fertile offspring. Initially the main reason for farming is to rear more livestock to make a profit-but at the moment the market is slow and farmers can't afford to invest in rearing a lot of animals, so instead they are stopping the reproduction of more animals. The reason for the control of this is because new offspring cost a lot of money to be cared for. The birth of a new animal requires a fully trained vet plus more excess vetinairy costs on top. The birth of a new cow for example would require pre-natal scan check-ups to ensure the safety of the cow and developing calf- the costs are building up before the new born has even arrived. Then on arrival the calf will require numerous vaccinations, which all add up to ensure the survival rate of the new born is very high.

Posted: 12-02-10 00:07 by Matthew Maguire

... 929 Words... It's being propper Naff!... when I've been trying to copy it from my hotmail... then to my Word document and then onto the forum. Enjoy :)

Posted: 12-02-10 00:09 by Matthew Maguire