Voiceover: In this video I want to talk about
the different types of neurotransmitters.
Neurotransmitters are molecules
that communicate information between neurons
and their target cells and chemical synapses.
There may be hundreds of different types
of neurotransmitters and they can be categorized
in a number of different ways,
but probably the most common
as to divide them up by their molecular structure
into amino acids, peptides, monoamines and others.
I'm gonna mention a bunch of chemistry terms next.
Don't worry about them if you don't know them
but if you are interested
there are many great videos on these topics
on the Khan Academy.
The first category of neurotransmitters
I'm gonna represent with these three
neurotransmitters right here
and this category is the amino acids.
Amino acid neurotransmitters.
Amino acids.
That's these three right here.
Amino acids have an amino group, this guy right here
and they have a carboxylic acid group.
This part right here.
There are lots of different types of amino acids
but just a few of them
function as neurotransmitters in the nervous system.
The next category of neurotransmitters
I'm gonna represent with this one right here
and these are the peptides.
Peptide neurotransmitters
and I'll just have this one representative here.
Peptides are actually polymers or chains
of amino acids.
A bunch of these amino acids
get strung together in these chains, these polymers
and we call them peptides.
Peptides are much larger molecules
than all the other types of neurotransmitters.
Sometimes people divide up neurotransmitters
just into peptides and they lump together
all the other neurotransmitters
and call them small molecule neurotransmitters.
The neurotransmitters in this row
will represent our next big category
which are the monomines.
Monoamine neurotransmitters, monoamines.
That's this whole row.
I've picked out five representative
neurotransmitters for the monoamines.
These are also sometimes called biogenic amines.
Either monoamines or biogenic amines.
The monoamines are organic molecules
with an amino group here and here and here,
here and here connected to an aromatic group
here, here, here, here and here.
The amino group and aromatic group
are connected by a two carbon chain,
this part here and here and here, here and here.
Some of the monoamines, these three.
Draw little stars next to these three,
are also called by a different name
and that name, and let me draw a little star.
That name is the catecholamines.
Catecholamines.
Catecholamines are a subgroup of the monoamines
and the catecholamines have a catachol group
which is this part right here
which has a benzine, this ring
and two hydroxyl groups.
Here's one hydroxyl group
and here's another hydroxyl group.
This catechol group, all the catecholamines have this group
these three right here.
There are many other types of neurotransmitters
that are not amino acids or monoamines or peptides
and this neurotransmitter right here
is gonna be the representative for that.
I'll just call this category other.
These are the other molecular types
of neurotransmitters.
Now I'm gonna introduce
some important neurotransmitters
in these different groups
and I'm gonna mention some of their functions.
Don't worry too much about their functions right now
because they do so many different things
in different parts of the nervous system
that we'll come back to all of that in other videos.
I just want to briefly introduce
the different important neurotransmitters
in each of these classes.
Starting with the amino acids.
Important amino acid neurotransmitters are this one
which is called glutamate.
Glutamate.
This one which is called gamma-aminobutryic acid
which pretty much everybody just shortens to GABA.
G-A-B-A for gamma-aminobutryic acid.
This one which is glycine.
Glycine.
Glutamate is the most common
excitatory neurotransmitter of the nervous system.
Let me just draw a big plus sign above glutamate here
because most of the time in the nervous system
when a neuron is releasing a neurotransmitter
that it's exciting its target cell
most of the time that neurotransmitter is glutamate
because it usually causes depolarization of target cells
so that it excites them.
GABA and glycine are the most common
inhibitory neurotransmitters of the nervous system.
Let me just write some big minus signs
above GABA and glycine
because they usually cause hyper polarization
of target cells and inhibit those target cells.
GABA is the most common
inhibitory neurotransmitter in the brain
while glycine is the most common
inhibitory neurotransmitter in the spinal cord,
so that the amino acid neurotransmitters
are really involved in most functions
of the nervous system.
Pretty much if you think of anything
the nervous system is doing
at some point in the chains and networks of neurons
glutamate, GABA and/or glycine are probably involved
in moving information through those networks.
There are many important monoamine neurotransmitters
but I'm just gonna mention these five
that are arguably the most important.
The first one here is serotonin.
Serotonin.
The next one here is histamine.
Histamine.
The next one is called dopamine.
Dopamine.
Then this one is epinephrine.
Epinephrine.
Right next to epinephrine is its close cousin
norepinephrine.
Norepinephrine.
All five of these are monoamine neurotransmitters
but these three dopamine, epinephrine and norepinephrine
are also called catecholamines.
The monoamines play a lot of different functions
in the nervous system
and in particular a lot of functions of the brain
including big things like consciousness, inattention
and cognition or thinking,
and emotions or us having feelings.
Norepinephrine is also released by some
autonomic neurons in the peripheral nervous system.
Many disorders of the nervous system involve
abnormalities of these monoamine
neurotransmitters systems,
and many drugs that people commonly take
affect the monoamine neurotransmitters.
There are many important peptide neurotransmitters
including a group of peptide neurotransmitters
called the opioids.
Opioids.
The opioids are a group within the bigger group
of the peptide neurotransmitters.
This one is one example of an opioid.
This is endorphin.
Endorphin.
The peptide neurotransmitters play a role
in many functions of the nervous system
but the opioids in particular
play a big role in our perception of pain.
A number of pain medications
affect the opioid neurotransmitters.
Last but definitely not least
are the other neurotransmitters.
Usually when there's an other category of anything
that means it's not very important
but in the case of neurotransmitters
there are some really important neurotransmitters
that are not amino acids, monoamines or peptides.
For example, this neurotransmitter right here
is called acetylcholine.
Acetylcholine.
Acetylcholine is definitely
one of our most important neurotransmitters.
It does a number of functions
in the central nervous system,
and then in the peripheral nervous system
it's released by most neurons
in the autonomic nervous system.
Let me just right ANS for autonomic nervous system
and it's released by neurons
called motor neurons
that synapse on skeletal muscle
and tell our skeletal muscle to contract
to make us move.
Again, don't worry too much about these functions
because in other videos
we'll go more into the structure
and the function of the nervous system
and talk about specific neurotransmitter pathways.
I just wanted to introduce
the different types of neurotransmitters here
and start to give you a feel
for the huge variety of functions
all these different neurotransmitters have
in the nervous system.