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The Effect of Recreational Drugs in the
Transmission Process in the Central Nervous
System
How do drugs affect your brain?
Why does a cup of coffee wake you up, and
aspirin stop your headache? Many drugs work
by copying or blocking the effects of naturally
occurring chemicals in your brain.
What is a drug?
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A drug is any chemical you take that
affects the way your body works.
Alcohol, caffeine, aspirin and nicotine
are all drugs. A drug must be able to
pass from your body into your brain.
Once inside your brain, drugs can
change the messages your brain cells
are sending to each other, and to the
rest of your body. They do this by
interfering with your brain's own
chemical signals: neurotransmitters
that transfer signals across synapses.
What is a synapse?
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When a nerve impulse reaches the synapse at
the end of a neuron, it cannot pass directly to
the next one. Instead, it triggers the neuron to
release a chemical neurotransmitter. The
neurotransmitter drifts across the gap
between the two neurons. On reaching the
other side, it fits into a tailor-made receptor on
the surface of the target neuron, like a key in a
lock. This docking process converts the
chemical signal back into an electrical nerve
impulse.
Altering your mind?
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Some drugs interfere with neurotransmitters
in the brain. These 'mind-altering' drugs
change our interpretation of the world, our
behaviour, and our mood. For example,
cannabis affects neurons releasing
acetylcholine, noradrenaline and dopamine.
LSD is a combination of an artificial acid and a
natural molecule found in the fungus Claviceps
purpurea (Ergot). LSD mimics serotonin action
in the brain, which seems to explain its
hallucinogenic effects.
What makes drugs addictive?
•
Doctors call a drug addictive if it makes you
dependent on the drug. Unpleasant
withdrawal symptoms appear unless you take
the drug. Addictive drugs also make you crave
them - you have an overwhelming urge to
continue taking the drug, even after
withdrawal symptoms have disappeared.
Reward Pathway: Where
pleasure overrides other drives.
Why are some drugs addictive?
•
Scientists think that all addictive drugs
activate the brain's 'reward system', by
increasing the release of the chemical
dopamine from neurons in key areas of the
brain. Dopamine release occurs after
pleasurable experiences, for example after
food or exercise. Drugs that artificially increase
dopamine release in this way may cause
craving for more. It is possible that some
people may have a genetic tendency to make
them develop drug addictions extremely
rapidly.
Dopamine releasing neurons
Classwork
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•
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Research the mode of action on the CNS of
one of the drugs below.
Nicotine
Cocaine
Cannabis
Links to Issues and Debates
Ethics-Most research into the effects of drugs comes
from animal studies.
Strengths and weaknesses?
Reductionism
Nature-nurture
The use of psychological knowledge within society
– e.g. understanding causes in order to deal with
them.
Can you identify where the issues and debates were in today’s lesson???????
Evaluate: Arguments About their Effects on
Transmission.
Strengths
Weaknesses
There is plenty of research:
It is reductionist:
The use of animals in research:
Credibility:
The use of brain scanning: