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Video transcript

in this video I want to talk about the different types of neurotransmitters neurotransmitters or molecules that communicate information between neurons and their target cells at 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 is to divide them up by their molecular structure into amino acids peptides mono amines and others I'm going to 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 going to represent with these three neurotransmitters right here and this category is the amino acids amino acid neurotransmitters you know acids that's these 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 and 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 going to represent with this one right here and these are the peptides peptide transmitters and I'll just have this one representative here peptides are actually polymers or chains of amino acids so a bunch of these amino acids get strung together in these chains these polymers we call them peptides peptides are much larger molecules than all the other types of neurotransmitters so sometimes people divide up neurotransmitters just into peptides and they love 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 mono amines mono amine neurotransmitters model means that's this whole row I've picked up five representative neurotransmitters for the mono amines and these are also sometimes called biogenic amines so either mono means or biogenic amines and the mono means organic molecules with an amino group here and here here here and here connected to an aromatic group here here here here and here in the amino group and the aromatic group are connected by a two carbon chain this part here and here in here here and here some of the mono means these three may draw a little stars next to these three are also called by a different name and that name let me draw a little star that name is the catecholamines cat a cold amines and so catecholamines are a subgroup of the mono amines and the catecholamines have a catechol group which is this part right here which has a benzene this ring and two hydroxyl groups here's one hydroxyl group and here's another hydroxyl group and so this catechol group all the catecholamines have this group these three right here and then there are many other types of neurotransmitters that are not amino acids or mono means or peptides and this neurotransmitter right here is going to be the representative for that so I'll just call this category other these are the other molecular types of neurotransmitters so now I'm going to introduce some important neurotransmitters in these different groups and I'm going to mention some of their functions but 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 will we'll come back to all of that in other videos but 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 amino butyric acid which pretty much everybody just shortens to gaba G ABA for gamma amino butyric acid and then this one which is glycine glycine now glutamate is the most common excitatory neurotransmitter of the nervous 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 is 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 so 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 I'm just going to 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 and right next to epinephrine as it's close cousin nor epinephrine norepinephrine so that all five of these are monoamine neurotransmitters but these three dopamine epinephrine and norepinephrine are also called catecholamines the mono means play a lot of different functions in the nervous system in a particular lot of functions of the brain including big things like consciousness and attention and cognition or thinking and emotion 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 neurotransmitter 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 and the opioids are a group within the bigger group of the peptide neurotransmitters and this one is one example of an opioid this is endorphin endorphin and 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 and a number of pain medications affect the opioid neurotransmitters and last but definitely not least are the other neurotransmitters now 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 mono means or peptides for example this neurotransmitter right here is called acetylcholine acetyl choline an acetyl choline 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 write ans for autonomic nervous system and it's released by the neurons called motor neurons that synapse on skeletal muscle and tell our skeletal muscle to contract to make us move so 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 but 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