Download about drugs

Neurotransmitters and Drugs
How Drugs Effect Your Brain
Acknowledgement:
http://www.sciencemuseum.org.uk/WhoAmI
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?
• 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?
• 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 tailormade 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?
• 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 work.
• 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.
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 sex, but
can also be induced by some
drugs. 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
What are stimulants?
• Stimulants are drugs that
make you feel more alert.
Caffeine, found in tea, coffee
and chocolate, is one example.
Many plants contain naturally
occurring stimulants (probably
to deter invading insects) that
in humans make the brain and
body more active. Many
stimulants, such as nicotine
and cocaine, are harmful and
addictive. Amphetamine,
which was first made a
century ago, is another wellknown stimulant.
Tea (left) and cocaine (right)
How does caffeine affect you?
• When you drink a cup of
coffee, the drug it contains
– caffeine – takes effect
within minutes. It then
blocks chemical signals in
your brain, stopping you
from feeling sleepy. In
moderate doses caffeine
also improves mental ability
– reaction times, memory
and reasoning skills. It takes
your body 3–5 hours to
break down caffeine, which
is why coffee at bedtime
may stop you sleeping.
Caffeine stops you from feeling sleepy.
What is nicotine?
• Columbus brought tobacco back
to Europe from America in the
late fifteenth century. When
tobacco smoke is inhaled,
nicotine is absorbed through the
lungs, and reaches the brain in
about 7 seconds. Nicotine works
by mimicking the actions of a
naturally occurring brain
chemical, acetylcholine, by
docking with its special receptor
molecules. Some of these
nicotine receptors in the brain
activate part of the 'pleasure
centre', which could be
responsible for nicotine's
euphoric effects
Nicotine works by mimicking the
neurotransmitter acetylcholine.
What are amphetamines?
• Amphetamines are all based
on the naturally occurring
chemical, ephedrine, found in
the herb Ephreda vulgaris.
Chinese people have used this
plant for over 5000 years to
treat asthma. In 1887,
chemists made amphetamine,
a synthetic substitute for
ephedrine. They found that
amphetamine affects the
brain, increasing alertness and
decreasing appetite. It
increases the levels of two of
the brain's chemicals,
noradrenaline and dopamine.
Ecstasy is an amphetamine derivative.
What are amphetamines used for?
• During the Second World War
many soldiers took
amphetamine to stay awake
while on duty. But it is an
addictive drug, with many
harmful side-effects. Doctors
still use amphetamine-like
drugs for certain medical
problems. Ritalin, for example,
is used to treat attention
deficit disorder (ADD) or
attention deficit with
hyperactivity disorder (ADHD)
in children. It increases
attention span, enabling the
child to concentrate better.
During the Second World War many
soldiers took amphetamines to stay
awake while on duty.
What is cocaine?
• Cocaine is a drug found in
leaves of the shrub
Erythroxylon coca. It
exaggerates changes caused
by at least two brain
chemicals, noradrenaline
and dopamine, increasing
alertness and causing
euphoria. Pure cocaine was
prepared in 1860 and was
hailed as a cure-all. Doctors
used it to treat anxiety and
depression until they
realised it was addictive.
Dentists once used cocaine to numb their patients'
mouths, but nowadays less harmful drugs are used.
How do painkillers work?
• When part of your body is
injured, special nerve endings
send pain messages back to your
brain. Painkilling drugs interfere
with these messages, either at
the site of the injury, in the spinal
cord or in the brain itself. Many
painkillers are based on one of
two naturally occurring drugs:
aspirin and opiates. Aspirin uses a
chemical found in willow bark,
used by the Ancient Greeks to
relieve pain. Opiates all work in a
similar way to opium, which is
extracted from poppies.
Painkillers interfere with the pain
messages sent to your brain.
What are opiates?
• Opiates, originally derived from
the opium poppy, have been used
for thousands of years for both
recreational and medicinal
purposes. The most active
substance in opium is morphine named after Morpheus, the
Greek god of dreams. Codeine, a
less powerful drug, is also found
in opium. Both these opiates
relieve pain, relax muscles and
cause drowsiness. All opiates
mimic your body's own
painkillers. Morphine is a very
powerful painkiller, but it is also
very addictive.
All opiates originally derived from the
opium poppy (Papaver somniferum).
What are the dangers of opiates?
• In 1821 Thomas de Quincy
described his experiences of
opium abuse in his book
Confessions of an English Opium
Eater. Later, morphine was used
widely as a painkiller during the
American Civil War, but many
veterans became addicted. In
1875, chemists trying to find a
less addictive form of morphine
made heroin. At first, no-one
realised how addictive heroin was
- it was used in cough mixture.
Addiction to heroin is now a
serious problem in many parts of
the world
Morphine was used as a painkiller during the American
Civil War, but many veterans became addicted.
What are endorphins?
• In the 1970s, John Hughes and
Hans Kosterlitz at Aberdeen
University discovered endorphins
in the brain. Endorphins are our
body's natural opiates, produced
when we experience stress.
Endorphin release from neurons
increases during exercise and this
is thought to promote a feeling of
well-being. Endorphin release has
also been linked with
acupuncture, the traditional
Chinese medical practice of
inserting needles into the body to
relieve pain.
Acupuncture chart dating from Ming Dynasty
What are sedatives?
• Sedatives are drugs that calm you
down. The oldest known sedative
is probably alcohol, used for
thousands of years. Surgeons
even used it as a general
anaesthetic before the arrival of
ether and chloroform.
Barbiturates were synthesised in
the 1890s and abused widely by
the 1900s. The search for safer
sedative and anxiety-reducing
drugs began after the Second
World War, eventually resulting in
the discovery of a family of drugs
known as benzodiazepines, which
include Valium.
Sedatives are drugs that calm you down