Hi, I'm Michael Corayer and this is Psych Exam Review and in this video I'm going to introduce some neurotransmitters and talk about some of
the functions associated with each neurotransmitter. Before I begin, it's important to remember that neurotransmitters have many
functions. They can work in different areas of the brain, different parts of the body, they can bind to different receptor types, so we want to
avoid thinking too simplistically about neurotransmitter function. We want to avoid this temptation to think about a really complex
issue like depression or schizophrenia as just being about the level of one particular neurotransmitter. So keep that in mind as I
discuss the functions that are associated with each of these neurotransmitters. The first neurotransmitter that I'll introduce is the first
neurotransmitter that was discovered and this is acetylcholine. This was discovered in 1921 by Otto Loewi
and what acetylcholine does, one of the things that acetylcholine or ACh does,
is that it's used in the body. It's used in the body to control muscle contractions.
So ACh is used at the point where nerves meet muscles, the neuromuscular junction,
and when ACh is released here it causes the muscles to contract.
But ACh is also used in the brain and it's used in areas that are associated with learning
memory and attention.
One of the ways we can see this role is when we have problems in these areas. So one of the things that happens in Alzheimer's disease
is that we have the deterioration of neurons.
When these acetylcholine producing neurons deteriorate in these areas of the brain, we see that patients have problems with learning,
memory, and attention. The next neurotransmitter that I'll talk about is one you may have heard of.
And this is dopamine.
One of the things that dopamine does is that it's involved in motor control,
fine control over our movement. And this happens in an area of the midbrain called the substantia nigra.
One of the ways that we can see this role is in Parkinson's disease.
One of the things that happens in Parkinson's disease is that we have deterioration of these dopamine-producing neurons in the substantia
nigra and the result is that patients have problems with controlling their movements, they have shakes and they have tremors and
these are the characteristic symptoms of Parkinson's Disease. But if you've heard of dopamine, it's probably not because of its
relationship with motor control and Parkinson's disease. You've probably heard of it because it's associated with pleasure and motivation.
This is a different area of the brain called the nucleus accumbens.
This is often called the "reward area" of the brain because in this area dopamine is released when we engage in behaviors that are
pleasurable and that are motivating, we're motivated to repeat these behaviors. So this is active when we eat food, when we engage in
sexual behavior and we'll see that it's also highly active when we use certain drugs like methamphetamine, cocaine, or heroin. These
trigger a massive release of dopamine in this nucleus accumbens area, and this is what makes these drugs pleasurable but it's also
what makes these drugs highly addictive. So we'll talk about the nucleus accumbens in more detail in a future video. We'll also talk about
dopamine when we talk about schizophrenia because one of the theories of schizophrenia is that some symptoms are associated with
elevated levels of dopamine in certain areas of the brain. The next neurotransmitter that we'll introduce is GABA.
This stands for gamma aminobutyric acid but we can just call it GABA.
GABA is an example of an inhibitory neurotransmitter.
What this means is that it inhibits function of the postsynaptic neuron. So when GABA is released in a synapse, it binds to receptors and
what happens when GABA binds to receptors is that it prevents positive ions from moving into the postsynaptic neuron.
It prevents the flow of these positive ions and this makes it harder for that next neuron to reach its threshold and that means it's going to
be harder for this neuron to fire. And we'll talk about GABA again when we talk about alcohol. We'll see that one of the things that alcohol
does is it causes GABA to be more active and this inhibits function of some brain areas.
Ok, the next neurotransmitter that we'll talk about is one that you may have heard of, and this is serotonin.
So serotonin has a number of functions, it's involved in sleep and dreaming,
it's also involved in appetite.
and actually most of the serotonin in your body, about 90% of it, is going to be found in your gastrointestinal tract. But it's also used in the
brain and if you've heard of serotonin, you've probably heard of it because it's associated with the regulation of mood.
So it's associated with disorders like depression.
You may have heard of an SSRI, an SSRI is an anti-depressant medication
and what this stands for is a selective serotonin reuptake inhibitor.
What this means is that this is a drug that inhibits the reuptake of serotonin.
So if you remember when I talked about what happens to neurotransmitters after they're released, we looked at a synapse here, so let's
say we have the release of some serotonin into the synapse. One of the things that happens to clear out the serotonin is that we have these
reuptake channels that work like a vacuum and they suck up the excess neurotransmitter. Well what an SSRI drug does, a selective serotonin
reuptake inhibitor is it gets in here and it blocks the reuptake channel. So it essentially clogs up the vacuum so that it doesn't work anymore.
This means that less serotonin is going to get sucked up into the presynaptic neuron. It's going to spend more time in the synapse and if
it spends more time in the synapse then it's going to be more likely to find its way down here to these receptor sites and influence the
postsynaptic neuron. OK so the last neurotransmitter that I'll talk about is norepinephrine.
Or if you prefer the British version, we can call it noradrenaline.
What norepinephrine does, is it's involved in arousal.
I don't mean sexual arousal, this refers to physiological arousal of the body, activation,
and in this case it's used in the fight or flight response, which is something you may have heard of.
So the fight or flight response refers to the body's response when threatened
it's an activation of physiological arousal
and when we face a threat we're activated to either fight this threat or flee from this threat. One of the things that happens during this fight
or flight response is that norepinephrine is released. And what norepinephrine does is it's involved in the regulation of heart rate. And in
this case, the fight or flight response, it's going to cause a massive increase in heart rate. You've probably experienced this any time
you're suddenly very fearful or threatened by something, you feel your heart pounding. That's the result of norepinephrine being released in
your body. And that's part of the fight or flight response, which we'll talk about in more detail in a future video. So this was a general
introduction to some neurotransmitters. Don't worry about memorizing all the names here, I know it's a lot, but hopefully this helps you to
get a grasp of some of the names of neurotransmitters and some of the functions behind them and we'll talk about all of these
topics in more detail in future videos. I hope you found this helpful, if so, please like the video and subscribe to the channel for more.
Thanks for watching!