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MCAT
Unit 7: Lesson 4
Neuronal synapsesTypes of neurotransmitters
Created by Matthew Barry Jensen.
Want to join the conversation?
I've heard that mast cells release histamines and that's what causes an allergic reaction, then why do we need mast cells or histamines?(4 votes)
Briefly (as much of their role in the body remains to be clear), mast cells aid in the immune response. Simple example: pathogen enters the nasal passage, mast cells are engaged, pathogen is swept away by excess watery mucus.(16 votes)
- If one has a lot of monoamines, does it mean that they are better thinkers (or more creative) than people who don't have that much monoamines?(3 votes)
- There's a lot to consider, but to put it bluntly, no. There is a fine balance that allows us to function well. Too much dopamine and that's schizophrenia normally (psychotic issues), too much serotonin and you'll be numb/apathetic and not attentive (sleepy) and etc. This is why mental issues are so difficult to solve. Nobody really knows what a good balance is and there's no way to measure your monoamine levels. You can get a monoamine blood test but it'll only give you an idea of neurotransmitter levels in your blood, not in your CNS, which is what matters.(22 votes)
So how exactly does the release of neurotransmitters from one neuron to another cause something like emotion or pain?(6 votes)
We don't know. We can see where activation happens with processes in the brain, we can measure what happens in small groups of neurons, but we don't understand how what happens in particular neurons translates into bigger effects in the brain and then into behaviours.(5 votes)
3:53In the text box, it says that Matthew meant to say 'glutamic acid', but does it really matter? In other words, would being deprotonated (and therefore calling it glutamate) make the NT non-functional?(6 votes)- Yeah the way I learned it is that Glutamate and Glutamic Acid are the same thing...(1 vote)
At7:03, isn't opioid an overdose drug?(3 votes)
It can be. Matthew is talking about what are called endogenous opioids here, which are substances that your body makes naturally. Your central nervous system and pituitary gland produce endorphins, which are opioids. The opioid drugs that people have overdosed on are refined from poppy plants or synthesized in a laboratory. The reason these drugs have an effect on people is because we have receptors for them, designed to work with the opioids our bodies naturally produce.(7 votes)
I see both NH2 and H2N. What's the difference? Are they bound in a different order? Or is one of them 3d?(2 votes)
I think they use H2N when it is on the left to show that it is the nitrogen bonded to the rest of the molecule and not hydrogen.(5 votes)
Would Steroids be classified as "Other"?(2 votes)
Sometimes it is hard to understand the question and I think that is why no one tackled your question. But here we have a video about neurotransmitters, such as norepinephrine, acetylcholine, GABA, etc. These are chemicals one neuron releases that bind to receptors on another neuron. They travel a short distance and affect one or at the most a very few other cells. Steroids are a large class of chemicals that are hormones. Hormones such as cortisol or testosterone, both steroids, are released by glands into the blood and they change the activity of many many cells. Hormones also bind to receptors on cells. So there are similarities between neurotransmitters and hormones as well as differences. And you can point to the adrenal medulla releasing norepinephrine and epinephrine so those neurotransmitters become hormones because they are travelling in blood and changing the whole body so we can fight or flee (adrenalin and nor adrenalin). Perhaps a medical dictionary will help. I will try to find a link, however, there is always wikipedia as a place to start. https://medlineplus.gov/mplusdictionary.html(2 votes)
- At1:35, how do you know which part is an amino acid?(2 votes)
- Amino acids are linked in chains to form peptides. The amino acids are bonded (or linked) at the amine end of one amino acid to the next amino acid at it's carboxlyic acid end of the next amino acid. This linking of amino acids makes a peptide through peptide bonds.
A good video explaining how amino acids make up peptides is located here: https://www.khanacademy.org/science/mcat/biomolecules/amino-acids-and-proteins1/v/peptide-bond-formation-and-cleavage(2 votes)
I know that the hexagonal shape in some of the neurotransmitter structures is benzene. However, I see that some have a pentagonal shaped object, too (ex., 2nd monoamine in the row, histamine). What exactly is that? Thanks!(1 vote)- Why do neurotransmitters not leave the synaptic cleft?(1 vote)
They actually do. It is just not mentioned in this video. Some neurotransmitters dissipate to other areas where they are needed, some are broken down by certain proteins, and some are injected back into the neuron for reuse.(2 votes)
3:53Video transcript
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.