Science

Drugs are chemicals that cause changes in the body. They can be divided into legal and illegal drugs. Drugs can also be medical (drugs taken to cure illness) or recreational (drugs taken because they have pleasing effects). Some drugs can be addictive – more and more is needed to achieve the same effect. Drugs can be separated into categories – solvents, painkillers, depressants and stimulants.
Types of drug

Drugs can affect nerves impulses, reaction times and behaviour.
Stimulants

Stimulants include caffeine - found in fizzy drinks, tea and coffee, cannabis and amphetamines such as speed. They increase the transmission of signals from one nerve cell to the next, which then increases alertness, heart rate and breathing rate. However, in the long term, stimulants can produce 'highs' and then extreme 'lows' or even depression. They can be addictive because the body needs a constant 'top-up' to maintain the effect.

Sedatives
Sedatives or depressants include alcohol and barbiturates (such as the prescribed drug amytal and the illegal GHB). Sedatives are also drugs prescribed by a doctor to help people sleep or to relieve the symptoms of stress. They slow down the nervous system and reactions.
Painkillers

Painkillers like paracetamol and aspirin are available 'over-the-counter' at pharmacies.
Painkillers or analgesics include paracetamol, aspirin, heroin and morphine. They block nerve impulses from the painful part of the body, or block nerve impulses travelling to the part of the brain responsible for perceiving pain.
Paracetamol is an effective painkiller but an overdose is very dangerous. An overdose damages the liver and can cause death.

Hallucinogens
Hallucinogens change the way our brains work, distorting our senses. This changes our response to what we see, feel and hear. LSD is an example of a hallucinogen.

About 114,000 people die every year as a result of smoking-related illnesses. All cigarettes sold now carry a prominent health warning.
Smoking during pregnancy is very dangerous as it reduces the amount of oxygen available to the growing foetus. This leads to an increased risk of:
miscarriage and premature birth
low weight of babies at birth.
Cigarettes contain about 4,000 different chemicals, many of which are harmful to the body.
Nicotine
Nicotine is the addictive substance in tobacco smoke. It reaches the brain within 20 seconds and creates a dependency so that smokers become addicted.

Carbon monoxide
Carbon monoxide combines with the haemoglobin in red blood cells and so reduces the ability of the blood to carry oxygen. This puts extra strain on the circulatory system, and can cause an increased risk of heart disease and strokes.
Tar
Carcinogens are substances that cause cancer. Tobacco smoke contains many carcinogens, including tar. Smoking increases the risk of lung cancer, mouth cancer and throat cancer.

The alcohol in alcoholic drinks - such as wines, beers and spirits - is called ethanol. It is a depressant, which means it slows down signals in the nerves and brain.
There are legal limits to the level of alcohol that drivers and pilots can have in the body. This is because alcohol impairs the ability of people to control their vehicles properly.

Short-term effects
Alcohol has short-term effects such as sleepiness and impaired judgment, balance and muscle control. This leads to blurred vision and slurred speech. Vasodilation occurs - blood vessels in the skin carry more blood - leading to heat loss.

Long-term effects
The long-term effects of alcohol include damage to the liver and brain. The liver removes alcohol from the bloodstream because it's a toxic chemical. Over time, alcohol consumption can lead to liver damage (cirrhosis).

Transplants
If an organ in the body has been damaged then it can be replaced by a healthy organ from a donor – someone who had healthy organs but very recently died from other causes.
A successful transplant has to have:
similar tissues from donor to patient
similar ages of donor and patient
similar locations as organs deteriorate quickly
Organ donation can be an ethical issue especially as the supply of organs is limited. An ethical issue is one that has rights and wrongs. In an exam you will be expected to discuss the ethical issues involved in:
liver transplants for alcoholics
heart transplants for the clinically obese.