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Science
Drugs
Drugs are chemicals that cause changes in the body. They
can be divided into legal and i llegal 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, painkil lers, depressants and
stimulants.
Types of drug
Drugs can affect nerves impulses, reaction times and behaviour.
Stimulants
Stimulants include caffeine - found
n 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
ncreases 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 ordepressants 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.
Coffee is a stimulant
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Painkillers
Painkillers oranalgesics 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.
Recreational drugs: tobacco
About 114,000 people die everyyear as a result of smoking-related
llnesses. 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 increasedrisk 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.
Painkillers like paracetamol
and aspirin are available
over-the-counter' at
pharmacies.
Warnings such as 'Smoking
can cause a slow and painfuldeath' are used to deter
people from smoking
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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
haemoglobinhaemoglobin : The red protein found in red blood
cells that transports oxygen round the body 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
ncreased risk of heart disease and strokes.
TarCarcinogens are substances that cause cancer. Tobacco
smoke contains many carcinogens, including tar. Smoking
ncreases the risk of lung cancer, mouth cancer and throat
cancer.
The images above compare a healthy lung to a smokers lung.
Tar deposits can clearly be seen clearly in the smokers lung.
Cigarettes and data
A healthy lung A smoker's lung, with tar
deposits visible
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There has been a lot of data
collected about the effects of
smoking. The graph shows the
correlation between cigarette
smoking and the incidence of lung
cancer. You may be expected to
nterpret graphs like this as part of
an exam question.
Recreational drugs: alcohol
The alcohol in alcoholic drinks -
such as wines, beers and spirits - is
called ethanol . It is a depressant,
which means it slows down signalsn 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
udgment, 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
t's a toxic chemical. Over time, alcohol consumption can lead to
iver damage (cirrhosis).
Transplants
f an organ in the body has been damaged then it can be
A correlation between
smoking and lung cancer
Alcoholic drinks
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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.
Now try a Test Bite.
Back to Revision Bite
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