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Types of neurotransmitters

Video 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.