Hormones in Humans: Reproduction & Metabolism (AQA GCSE Biology): Revision Notes
Contraception
Contraception helps control when people have babies. There are different ways to prevent pregnancy, and they work in different ways. Understanding these methods is essential for making informed reproductive health decisions.
Each contraceptive method has different levels of effectiveness, side effects, and suitability for different people. It's important to consult with healthcare providers to choose the most appropriate method.
Oral contraceptives (the pill)
The contraceptive pill contains two important hormones called oestrogen and progesterone. These are the same hormones that naturally control a woman's menstrual cycle.
How the pill works
The hormones in the contraceptive pill work together to prevent pregnancy through a carefully controlled process:
The Pill's Mechanism of Action:
- The hormones stop the release of FSH (a hormone that helps eggs develop)
- Without FSH, eggs don't mature properly
- No mature eggs means no eggs can be released from the ovaries
- If there's no egg, pregnancy cannot happen
Side effects of the pill
Taking the pill can cause some unwanted effects that users should be aware of:
Potential Side Effects:
- Higher blood pressure
- Blood clots (thrombosis)
- Increased risk of breast cancer
These risks vary between individuals and should be discussed with a healthcare provider before starting the pill.
Early pills had much higher hormone doses than modern ones. Today's pills are safer and cause fewer side effects due to improved formulations and lower hormone concentrations.
Surgical methods
These are permanent ways to prevent pregnancy through small operations. Both procedures are considered highly effective but require careful consideration due to their irreversible nature.
Female sterilisation
Female sterilisation involves blocking the reproductive pathway to prevent pregnancy:
- Doctors block or seal the oviducts (tubes that carry eggs)
- This stops eggs from reaching sperm
- Women still have normal periods after this surgery
- The operation is very difficult to reverse
Male sterilisation (vasectomy)
Vasectomy is a minor surgical procedure that prevents sperm from reaching the semen:
- Doctors cut the sperm ducts that carry sperm
- This stops sperm from mixing with semen
- Men can still ejaculate, but there are no sperm present
- Like female sterilisation, this is hard to reverse
Post-Surgery Contraception:
Both men and women need to use other contraception for a few months after surgery until it becomes fully effective. Sperm can remain in the system for several months after the procedure.
Other methods
Barrier methods
These methods physically stop sperm from reaching an egg and provide immediate protection when used correctly:
Types of Barrier Methods:
- Condom: A thin rubber sheath that goes over the penis to collect semen
- Diaphragm: A thin rubber cap that covers the woman's cervix to block sperm
Both methods work better when used with spermicide - a chemical that kills or disables sperm.
Intrauterine device (IUD)
The IUD is a long-term reversible contraceptive that offers years of protection:
- A small, T-shaped plastic and copper device
- A doctor fits it inside the uterus
- It stops sperm and eggs from surviving
- May also prevent fertilised eggs from implanting
- Normal fertility returns when a doctor removes it
IUDs can provide effective contraception for 3-10 years depending on the type, making them a cost-effective long-term option for many women.
Natural family planning
This method requires careful timing and dedication from both partners:
- Couples avoid sex when the woman is most likely to get pregnant
- They work out when an egg might be released during the menstrual cycle
- This method requires careful timing and isn't always reliable
Natural family planning has a higher failure rate compared to other contraceptive methods and requires consistent monitoring and commitment from both partners.
Key Points to Remember:
- Hormonal contraceptives work by stopping eggs from developing and being released
- Surgical methods are permanent but very effective ways to prevent pregnancy
- Barrier methods physically stop sperm from reaching eggs
- IUDs can prevent pregnancy for several years and are reversible
- Natural family planning requires careful timing and isn't as reliable as other methods
- All methods have different effectiveness rates and some have side effects to consider
- Consulting with healthcare providers is essential for choosing the most suitable method