all right so in this video we're going to talk about the different types of neurotransmitters now neurotransmitters are the chemical language of your nervous system and uh scientists identified over 50 of these we'll talk about some of the the more abundant ones in this uh section and uh it turns out that most neurons in your body actually produce more than one neurotransmitter so uh these neurotransmitters can be released you know based on different influences like excitation frequency or other neurot transmitters and um we can classify these neurotransmitters based on chemical structure and function so the one we've talked about a lot already because it relates to the neuromuscular Junction was acetylcholine so it's the first identified and also the best understood we've talked about it at neuromuscular Junctions but you also find this used pretty abundantly like around your peripheral nervous system in the central nervous system in fact there's a whole subdivision of your autonomic nervous system that we'll talk about that relies on acetylcholine now uh we find that acetylcholine synthesized from acetic acid which is essentially vinegar and choline by an enzyme called choline aceto transferase there's also an enzyme called acetyl colon esterase that actually breaks down acetylcholine and you find acetyl Colon esterase around your body but especially abundant within the synaptic clifts that way these enzymes can break down and remove the signal and to prevent uh you know excessive excitation now the biogenic amines include your catacol amines and indolamines colines are like norepinephrine epinephrine which uh are basically you know part of your sympathetic or fight ORF flight response as well as dopamine which is involved with movement now all of these types uh dopamine norepinephrine epinephrine they're part of the same class of of neurotransmitters because they're all made from a specific type of amino acid called tyrosine now the indolamines include serotonin and histamine and serotonin is made of tryptophan in fact serotonin is five hydroxy tryptophan and then histamine made from histadine and so what's interesting then is that these biogenic amines are actually made from amino acids so the catac colines and indolamines are basically just made from different types of amino acids now they're all widely used in your brain and they play lots of different roles and things like movement emotional behaviors and even setting the biological clock in fact histamine is a really important type of of neurotransmitter and just chemical that's involved with uh things like digestion and uh even inflammation now uh we see that some of these uh biogenic amines are used by your autonomic nervous system and imbalances are associated with mental illness so the amino acids that uh can be used directly as neurotransmitters are things like glutamate aspartate Glycine and Gaba and these aren't converted like these are just amino acids that your body uses for signaling whereas with the biogenic amines and the indolamines those were converted from amino acids these ones are just just just how they would normally be so uh glutamate and aspartate are excitatory neurotransmitters and then Glycine and Gabby are both inhibitory now um neurotransmitters can also be made of peptides and these can be strings of amino acids that have diverse functions things like substance P are actually you know mediators of uh pain signals and the endorphins are uh involved with modifying pain perception there's like bet endorphin dorphin and en keyins these are actually natural opiates so they're actually natural painkillers now gut brain peptides like somatostatin and kosis kinin play a key role with regulating digestion so the purines are actually uh you know molecules that are similar to ATP and in fact even include ATP and you find that uh ATP is actually used but as a neurotransmitter in certain areas especially in the peripheral nervous system like with your taste buds your taste cells use ATP to transmit taste information it's kind of weird here now adenosine is actually a pretty potent inhibitory neurotransmitter in the brain and peripheral nervous system in fact we can use adenosine to uh slow down heart rate but what's interesting here too is that caffeine blocks adenosine receptors this is one of the reasons why caffeine is a stimulant because it actually blocks the neurotransmitter that would normally inhibit your nervous system so uh the way that that these work is that can actually induce calcium influx into asites and this plays a role in modulating synapses within your brain now uh gases and lipids can also be used as neurotransmitters in fact there's a whole class called the gasotransmitters like nitric oxide carbon monoxide and hydrogen sulfide and although these are gases they're also neurotransmitters so they bind with G protein coupled receptors and uh Nitric oxid is actually involved with learning and memory uh as well as brain damage and stroke patients and smooth muscle relaxation uh hydrogen sulfide acts directly on ION channels to alter function of different cells now the endocannabinoids are um you know class of molecules that are actually made by you know cells in your body including the nervous system but they act as the same receptors as THC or tetrahydrocannabinol which is an active ingredient in marijuana now your body makes similar molecules and uh they're the most common G prot coupled receptor in the brain now these types of molecules are lipid soluble which means they accumulate within your fats and they're synthesized on demand and they're believed to be involved with learning a memory and they see seem to play important role with neuronal development uh controlling appetite in suppressing nausea this is why you know THC is used for medically in some cases with you know appetite control like if someone is undergoing chemotherapy and they have poor appetite that they need to eat you know THD can be effective for that as well as suppressing nausea that might be associated with other medications now uh neurotransmitters exhibit pretty great diversity of functions and we can uh group these based on their effects and their actions now the effects could be either excitatory or inhibitory and neurotransmitters that are excitatory we say that are depolarizing and therefore cause epsps neurotransmitters that are exit sorry inhibitory are hyperpolarizing and therefore cause ipsps now the effect is the ter by which neurotransmitter binds to which receptor so we say that Gaba and glycine are typically inhibitory because these types of neurotransmitters bind into receptors that gate or allow for the flow of potassium and chloride ions now glutamate is typically excitatory because it can bind to receptors that gate sodium or calcium ions and acetylcholine and norpine bind to different receptor types and actually have different effects so acetylcholine is excitatory at the neuromuscular jum Junction but acetool is actually inhibitory in cardiac muscle which is kind of interesting and what makes the same neurotransmitter have different effects is the fact that that at the neuromuscular Junction acetylcholine binds to uh nicotinic receptors and in cardiac muscle acetylcholine binds to muscarinic receptors and these receptors have different effects on those target cells now the actions can be either direct or indirect if it's a direct effect we see that neurotransmitters bind to the channel and it opens those Lian ated ion channels this promotes pretty rapid responses by altering membrane potential and examples of this would be like acetylcholine and amino acids now an indirect action would be where a neurotransmitter acts through intracellular second messenging mechanisms like gr protein coupled receptors now the effects of these indirect secondary messaging systems are broader and longer lasting and so they have very similar effects as hormones and so the biogenic amines neuropeptides and gases typically act on these G protein couped Pathways so uh neurom modulators are chemical messenger released by neuron that doesn't really directly cause epsps or ipsps but rather affects the strength of synaptic transmission so what we see then is a neuromodulator can influence the synthesis release or degradation or even reuptake of a neurotransmitter so it indirectly kind of has an effect on the target cell now it can also alter sensitivity of the post membrane and uh you know make the postoptic cell either more or less sensitive to that neurotransmitter now these can be released as a paracrine so their effect is usually only local so neuromodulators are typically released just like a local area for synapses now in terms of the types of receptors we have we have the channel link receptors now these are liand gated ion channels their action is immediate and brief and these can be excitatory or inhibitory the channel receptors are excitatory if they gate sodium so that sodium influx causes depolarization ation and the channel receptors can be inhibitory if they gate things like chloride or potassium because a chloride influx would cause hyperpolarization as with a potassium efux it would also cause hyperpolarization now the reason why these actions are immediate is that they're you know they're basically just allowing ions to flow and they're brief because the channels don't stay open very long so what we see here is an example of a Lian GED ION channel where neurotransmitter can bind and once the neurotransmitters bind ultimately this channel opens up allows for ions to flow and this could be an example of like acetylcholine binding to a nicotinic receptor which allows for sodium to flow into the cell if sodium rushes into the cell you're bringing in positive charge which makes the inside of the cell more depolarized so you'd call this excitatory current now gr protein coupled receptors are uh a type of response that's indirect more complex it's slow but the response is often prolonged now this involves transmembrane protein complexes where a neurotransmitter binds to a receptor it causes a molecular change in the change uh shape of this receptor that uh initiates a chemical reaction within the cell so examples of G protein coupled receptors are things like muscarinic receptors uh the adrenergic receptors for adrenaline and so those are the ones that would actually respond to the biogenic amines like epinephrine and norepinephrine or even receptors for neuropeptides so the mechanism of these is that neurotransmitter binds the G protein coupled receptor and activates this G protein now activated G protein controls the production of secondary Messengers like cyclic cyclic gy diog glycerol or D and calcium now these second messengers can actually open or close other ion channels they can activate protein kinases they can phosphorate other channel proteins and even activate genes that induce protein synthesis so what this G protein couple mechanism looks like is when a neurotransmitter binds to its receptor here we get a we get in a Cascade of chemical events where this G protein becomes activated by GTP now GTP binds the G protein and this complex actually travels through the inner leaflet of the membrane over to another enzyme called ad denate cyclas now once a denate cyclas is activated it converts ATP into a molecule called cyclicamp and Iden cyclace is actually an enzyme so it actually can convert a tremendous amount of ATP into cyclicamp now cyclic is the secondary messaging molecule and what cyclicamp can do is actually come over here and actually activate other enzymes cyclic can actually open or close different ion channels it can also uh alter the shape of of uh proteins that can change gene expression so there's a wide range of effects