M6 Biology – Neurotransmitters,
The Brain and Addiction!
Multi-Purpose Chemicals!
1) Many chemicals that work as neurotransmitters
in the CNS and PNS also have functions as
___________________ in other parts of the body.
Epinephrine, for example, is another name for
___________________ which functions as both a
hormone in the body and a neurotransmitter in the
brain! The exact role of each neurotransmitter is
sometimes difficult to determine; there are many of
them, and some of their functions are still
mysterious.
Figure 2 Explained!
2) Neurotransmitters are
secreted into the
_________________
between nerve cells,
where they can bind
with specific
__________________
on the dendrites (or
sometimes the cell body)
of another nerve cell.
Multi-Purpose Chemicals!
3) This happens very quickly, converting an
electrical signal (from a nerve impulse) into a
chemical one and back again. The
neurotransmitters are then quickly
_________________________ (with the help of
enzymes), removed, or re-absorbed (called ‘reuptake’) and used again.
Figure 2 Explained!
4) Dopamine is an important
neurotransmitter utilized in the CNS. It
creates what we perceive as happiness,
pleasure, euphoria, joy, and many other
positive feelings… It is like a reward our
brain gives us when we do something
‘good’ or that our CNS perceives as
beneficial!
a) What is your happiest memory? Write it
down.
b) How do you ‘feel’ when writing and
thinking about that time of your life? Was
dopamine released (either now, or when that
memory was created?)
Thinkin ‘bout food!
c) Critical Thinking: When you eat a meal high in sugar
or fat, large amounts of dopamine is produced. Can
you think of an evolutionary reason why this would
happen?
Dopamine and Addiction
5) Foods that are high in sugar and fat can be
classified as ________________ substances
because of their release of excessive dopamine!
Our CNS becomes dependent on the dopamine
released when we eat. When too much
dopamine is produced, our brain shuts down
some of the dopamine receptors, requiring us to
eat more and more to achieve the same
euphoric feeling – just like with certain drugs!!
Dopamine and Addiction
6) Some drugs work by mimicking
neurotransmitters, by preventing their
destruction, or by ___________________ their
removal or re-uptake from the synapse.
Effect of drugs…
7) Cocaine, a stimulant, blocks the reuptake of
serotonin, norepinephrine, and dopamine. This
causes a ‘sensory overload,’ a feeling of intense
pleasure, confidence, energy, and a numbness
to feelings of pain!
7a) + b)
Is cocaine addictive?
Explain why!
Depressants…
8) Depressants like alcohol, barbiturates,
cannabis, or opium, have the opposite effect of
stimulants like cocaine; they make you feel tired,
lazy, slow your reaction rates and make you
much more sedative and relaxed.
Opiates!
8) Opiates like morphine, heroin, or oxycodone
are powerfully addictive
______________________. They work by closely
mimicking endorphins, and can actually bind to
endorphin receptors in our CNS.
a) What effect would this have on our body?
Use the chart on the previous page
b) Explain why this is useful for hospitals or
recovery from serious injury.
Terms
• Mimic – to copy or imitate closely.
• Inhibit – to stop, block, hinder or restrain
• Re-Uptake – Neurotransmitters are brought
back inside the axon terminal through
transport channels (re-uptake channels).
Therefore re-uptake inhibitors…
block, stop, hinder or restrain the normal action
of these re-uptake channels.
Terms
• Stimulant – cause more neurotransmitter
molecules to diffuse across the synapse, to
remain in the synapse longer, or work as
neurotransmitter mimics.
– E.x. nicotine, caffeine, ecstasy
Terms
• Depressants stop the next neuron from
sending nerve impulses – they bind to the
receptor molecules it needs to respond to the
neurotransmitter molecules.
– alcohol, solvents, temazepam, opiates (heroin,
morphine, opium, oxycodone)
Terms!
• Addiction: craving for something intensely,
loss of control over its use, and continuing
involvement with it despite negative
consequences.
Terms
• Dependent: requiring or wanting something in
order to feel ‘normal’ again. A need.
• Painkiller: – blocks nerve impulses
Physical vs. Psychological Addiction
The word “addiction” is derived from a Latin
term for “enslaved by” or “bound to.”
Addiction changes the brain! It alters or
modifies the way it registers pleasure and
corrupts normal drives like learning and
motivation!
Some addictive substances have physical
consequences too!
Meth Users (Crystal or ‘ice’)
Physical Addiction
When your body becomes so dependent on a
substance or drug your cells cannot function
without it. The withdrawal effects—nausea,
vomiting, headaches—are the body telling you it
needs more of the substance to return to its
new (artificial) state of normalcy.
Withdrawal…
• Cold sweats, shaking,
vomiting, etc…
• Sometimes ‘stopping cold
turkey’ isn’t safe.
• Slow decrease in
amount of drug
taken is the best
way to quit!
Psychological Addiction – It’s all in
your mind!
The brain registers all pleasures in the same way,
whether they originate with a psychoactive
drug, money, a sexual encounter, or a satisfying
meal.
• Review: Excess dopamine release forces the
brain to ‘shut down’ dopamine receptors.
• Tolerance results, and more drugs are
required to provide the same effects.
Addiction…
• Normal activites feel boring, un-stimulating
(because they are, compared to the drug!), or
repetetive.
• The drug becomes your #1 priority, the only
way to feel ‘normal’ again.
• Family life, relationships, work, etc., can all
suffer when they come #2 to drugs!
Less obvious addictions...
• Gambling, war, and other high-risk activities
can also be addictive!
• The risk creates an adrenaline ‘rush’ (during
the activity).
• Surviving or finishing the activity usually
results in a flood of dopamine release as the
adrenaline is cleared away.