hi the topic this video is communication between two neurons we're picking up where we left off with the um screenshot in front of you right now parts of a neuron and we talked about what the parts were and generally what their function um each of their functions is and now we're going to talk about how they work together so that one neuron AKA nervous system cell which um most of which are in the brain some spread throughout the body in the senses but how one neuron communicates with another neuron okay let me point out quickly what we're doing now is a means to an end because literally everything in your life every thought every feeling every Behavior every memory anything that happens breathing heartbeat everything that happens in your life happens because groups of neurons each coded with particular information particular functions because groups of neurons are active together they're connected by axons by wiring by circuits um and when this group of neurons that are connected together are all active together what we call fire together something happens we take a breath our heart beats we we we're angry we um lift our hand to scratch an itch on our head everything involves a group of neurons firing together a group of connected neurons firing together and out of that comes a feeling a thought a memory in action Etc so what's my point we can't understand how a group of 15,000 neurons connected to each other all communicate with each other by what we call firing off a message we can't understand how 15,000 neur neurons communicate with each other if we don't understand what a neuron is and how one neuron communicates with another neuron which is why we're starting with the parts of a neuron and we're going to move on to how one neuron communicates with another and then the Final Act of this play is neural networks and what the heck they are well I've just described them but that's where that's going to be the finale of this um this series of videos what are neural networks and how do they work in our brain now we talked about parts of a neuron let me let me just remind you that the cell body um does the general maintenance for the cell where the axon transmits information the dendrites receive information the Soma does enal maintenance the Soma absorbs nutrients and oxygen from the blood um it crosses the cell membrane and it's the food and the oxygen which is necessary for the cell to stay alive and and do what it does all living things need oxygen why that's just the way it is but without oxygen living things die they need two things actually three things all living things need oxygen water and what we call nutrients um or what we call colloquially food okay all living things need those including a cell body okay and so somehow a individual cell which is the smallest living unit okay there are organisms that are single cell bacteria virus we're mult multicellular with cells having many different functions all working together to Keep Us Alive but in order for that to happen every cell needs to stay alive and it like all living things needs oxygen it needs water and it needs food and those things are absorbed through the membrane the walls of of the cell body into the cell so that the cell can do the things it needs to do to keep the cell Al alive which keeps Us Alive just wanted to add a little bit to to the cell body okay all these things we talked about now we're going to put them together into communication between two neurons sorry for the little Gap there I had to to pause the recording for a moment and in order to do that I've got to find the button and to push but now I'm back okay what you see in front of you on the left is is a neuron it's it's an illustration of a neuron if you were to see one under a microscope it it looks similar to this but this is a drawing and um you've got a 100 billion neurons none of them probably look exactly like this because they're more complex but they have the same body parts I mean they have the same Parts they all have a cell body with a nucleus in the middle and they all have one axon with terminal buds at the end so that it the message can be delivered many different neurons um and they all have dendrites Around the Edges full of receptor sites that's review we've already talked about that so the question is how does this neuron in the left communicate with this neuron on the right and all we've got with the neuron in the right is the cell body because it's the dendrites on the surface of the cell body made up of receptor sites that actually receive the information okay first of all you see two neurons here one is transmitting and the other is receiving the pre synaptic neuron is the one in order for communication between communication you need at least two neurons and the one transmitting we call the pre synaptic because it's before the synapse and it PR synaptic transmits to post synaptic neurons okay post synaptic neuron receive the information okay so you have a pre synaptic transmitting information to a post synaptic there's nothing inherent about a neuron that makes it pre or post synaptic its designation as pre or post synaptic is relative to another neuron so this neuron is pre synaptic relative to this neuron this one is post synaptic but you will notice this neuron is receiving information from another neuron over here so this neuron is post synaptic relative to this neuron this neuron is both pre and post yeah because that designation is describing it relationship with another neuron and its relationship to this neuron is its preseptic it's relationship to the neuron over here it's post synaptic okay you need to be able to answer the question why is a designation pre or post not inherent it's nothing you know that they're born with uh you talk about a cell being born actually it's born because a cell divides into two cells and a new one is is born um very different than the way humans are born though cell division is involved there as well okay so you need to understand the difference between pre synaptic and post synaptic neurons and why this is not an inherent designation it's all about their relationship with another neuron now the synapse um and I didn't know which of these to do first the neurotransmitter or the synapse the neurotransmitter is the chemicals that travel across the synapse into and communicate information they're like the words when you're talking except in this case it's it's a chemical you've heard of some neurotransmitters like dopamine which is associated with pleasure uh serotonin which is associated with um depression um as also is uh norepinephrine but we'll talk about that a little bit later in the course but the at the axen helic this door here when this neuron um is going to communicate with this neuron over here the door has to be open and a chemical jolt of of of an electrical signal energy you open that door the aent heal ilc and electricity goes down the axon just like it does in a wire to a lamp or any other electrical Appliance when it gets here what it does is it excites these little sacks full of neurotransmitters and the result is neurotransmitters are released it down to the terminal buds okay um releas and I'm I'm actually they're in the terminal buds I misspoke the electricity activates the the the end of of the axon and there's little bags called vesicles full of neurotransmitters and when the electrical signal hits one um if there's dopamine stored in in this terminal bud it's released a gate is opened up and it travels out into a small space here's another one it looks like this terminal bud is coming into contact with the dendrite just like here this dendrite it isn't it's real close to it and the chemicals are released into this space called a synapse the synapse is the location or the space between a terminal button and a dendrite and this is where the chemical um neurotransmitter is released and if it comes in contact with the the the appropriate receptor site if there's a receptor site available on this dendrite for dopamine and dopamine comes in contact with it it will bind the receptor site and send the information to this post synaptic neuron okay it binds okay it doesn't enter it just gives its information once it's bound and the information is gone the neurotransmitter releases back into the synapse it's done its job but the neurotransmitters they're valuable they're expensive to make they're made out of amino acids what proteins are made out of so you don't want to waste the neurotransmitters so the preoptic the pre synaptic uh um neuron has like little vacuum cleaners that vacuum up the neurotransmitters bring them back in and and recycle them and use them again okay now I've explained all this let's move down to the terms okay we talked about a synapse that Gap that space where the neurotransmitter the chemical enters into this empty space um in a space right near the dendrite and if the appropriate receptor site is available it binds and it sends its message so you also understand what a neurotransmitter the the topic of the um next video is neurotransmitters in the brain so we'll we'll learn more about them one thing that that's true is what's called an action potential look if you fire a gun the bullet's going to make it out of of the barrel of the gun it's not going to get stuck along the way there's enough energy to get the bullet all the way out of the barrel of the gun the same is true this trigger okay this axon hilic when it opens up it's like the firing of a gun and this transmission of energy is called an action potential okay I don't know whether that's the best name but that's what it's called all that means is once that door is opened once the electrical electrochemical energy has been fired along an axon it's going to make it all the way into the synapse It's All or Nothing it doesn't even a whale who has to move its tail at at 30 feet away at the other end of its body when the neurons in its brain that control the tail when they're when they fire an action potential it always makes it the entire length of the whale's body to the end of the axon and and the chemical is released and and then it it's eventually going to activate muscles either expand or contract and and and the tail will move okay so you need to understand what an action potential is and why it's characterized or described as an All or Nothing event this this part's simple one of two messages can be delivered from a pre synaptic to a post synaptic one is going to te tell it pass the information on so an excitatory synaptic input is going to increase the likelihood that the post synaptic cell will fire will have an action potential and send the information on to another neuron what if we want to settle down what if you just run 100 yard dash and your respiration neurons are going nuts you're breathing like crazy your heart's beaten fast and you need to settle down well the message that scent is an inhibitory synaptic input it slows things down it slows down your heartbeat and your breathing okay the ab so inhibitory decreases the likelihood of a post synaptic cell firing so when you get excited and get active mentally or physically you've got a lot of excitatory messages when it's time to settle down and relax you've got a lot of inhibitory story and these two things work in opposition to each other to get us moving and to settle us down they work together now two neurotransmitters I want to point out to you one is glutamate it's one of the ones we're going to talk about in the next video glutamate is the main excitatory uh um neurotransmitter so when it comes to cells being told to pass on the information to fire the messengers most likely glutamate when it comes to telling the the the cells um no don't fire settle down the messenger most likely is Gaba and this stands for a long name which you don't need to know but you need to associate glutamate with excitatory synaptic inputs telling the neuron to Fire and you need dissociate Gaba with inhibitory telling it not to fire reuptake is that process I referred to pre synaptic cells taking back neurotransmitters from the syap synapse recycling both those That Never Bound they just there wasn't an available receptor site or others after post synaptic activation which are released back into the synapse many drugs work by blocking the re uptake sites which leaves the neurotransmitter available longer which increases the likelihood it's going to bind okay um selective serotonin reuptake Inhibitors the way proac works is it blocks the receptor sites from the pre synaptic neurons that are releasing serotonin it stops the serot Onin from being sucked back in so the serotonin is available longer and more likely to bind to the post synaptic neuron and activate it in either an excitatory or an inhibitory way everything I said should make sense to you if you understand this whole process okay that's the end of this video no it's not I'm sorry one other thing is part of this video now that we know how one neuron connects with another neuron we're now ready to talk about neuron networks I already talked about them okay neurons working together in groups sometimes as many is tens of thousands for you to have a thought or a memory or to think about things so don't need to talk about this a lot it should be pretty clear to you at this point just based upon what's right in front of front of your face and based upon understanding what we've already talked about but neural networks which you will hear people talking about in your life because it's a main topic of conversation um not not not only within science but you will read it in articles and hear it on videos podcasts but neural networks are groups of interconnected neurons and their connection is by way of wiring the wires are axons and they're circuits they're circuits for energy to travel from one neuron to another and then these groups fire in a coordinated Manner and that's what produces the brain activity necessary for Sensations thoughts decision making actions feelings memories all bodily functions thousands to millions of neurons must fire in unison to produce the slightest thought feeling action or bodily function living life results in new or modified networks your networks run your life and when you have new experiences sometimes they need to be rewired okay um um so all stored experience everything you've learned from your life's experiences is stored in these networks changes in the the brain the result from Storage of new life experience or modified knowledge of what we experienced in the past it it's changes in neural networks the physical basis for all new and modified Knowledge and Skills all memories is modifying neural networks habits all habits are well-developed skills or easily remembered information which are both habits they're all reflective of the activation of Highly Effective neural networks if you do something habitually you've got a really well-formed and functioning neural network what if you stop doing something that's habit I played basketball my whole life I stopped playing um when I was around 60 years old because of a fear of injury and and the recovery time I would get sore after playing so I stopped now I had dribbled a basketball almost every day of my life and shot a basketball almost every day of my life but about I don't know in my late 60s I was at a playground with my grand kids and there was a basketball in a basket and we started shooting it and I shot a few shots that were routine and I I I came up short I I really had to concentrate to make a free throw I couldn't believe it I used to be able to whip off 10 in a row or at least nine out of 10 um why because the neural networks um parts of them I hadn't used that are specific to shooting a basketball and if if the neurons aren't used the brain isn't going to waste food on them and they atrophy they kind of wear away it's called pruning okay it's called pruning your brain is very plastic it's built into modification to learn new things to form habits and to not waste food when you stop doing something on maintaining a very well-formed and functioning neural network that you don't use anymore okay so to a certain extent uh of neural networks it's a use it or lose it because your brain is going to eliminate unused therefore unnecessary neural connections okay and then of course we also call that synapsis because that's the place where the information is exchanged so sometimes it's called synaptic pruning sometimes it's called neuro pruning the bottom line is if you don't use something over time it's lost synaptic neural pruning is very active from Early Childhood through adolescence because a lot of the stuff you learn is wrong a lot of the skills you develop um are are open to change so that you can be more effective so there's a whole lot of pruning that occurs in childhood and Adolescence for someone my age uh most of the pruning is to not to new things making networks more effective a little bit but not a lot um it's more um pruning things I no longer use so you need to understand the concept of synaptic or neuro pruning what it is why it occurs and why a lot of it occurs in early childhood and Adolescence and you need to understand brain plasticity when people say you may have heard we only use like 10% of our brain it's not like 90% of our brain is active it's like 90 probably 99% of the potential in your brain isn't utilized um unless you use it to um um form certain skills um if if if you learn something new it's why older people to prevent cognitive decline or encourage to learn to play an instrument or learn a new language do something new it's built into my job I'm always learning new things as I keep up with all the different areas of psychology that I have to to teach intro plus the specialized courses I teach like psychopharmacology and counseling theory and practice developmental psychology all those things I have to keep up with so um my brain gets a lot of exercise okay brain plasticity the brain's capacity for for modifying both function and structure it it will change the function of of of of existing U networks or create new ones and certainly change the structure through the um neurogenesis um new neurons being born and neural pruning which is leads to the death of some neurons so your brain is equipped to learn to modify both structure and function in response to experience Dave if you have any questions let me know I'm ending this video