Central and Peripheral Nervous System

hi. In this lesson, we'll talk about the structure and organization of the nervous system. Now the nervous system can be divided between the central nervous system and the peripheral nervous system. And the central nervous system is composed of the brain and spinal cord, and everything else is considered part of the peripheral nervous system. Now we often classify the tissue found here as being either gray matter or white matter, and that distinction is based upon whether or not the tissue mostly consist of neuron cell bodies or militated axons. Remember that Meilan is a fatty substance, coating the outside of axons and, just like fats, appear to the naked eye. When you look at a bunch of myelin ated axons, they just kind of look white from all the fat, whereas the cell bodies take on that gray appearance and you can see that in the brain. The outside of the brain, for the most part, is made up of gray. Matter can see it all along here, this darker stuff along the outside, that's all gray matter. Of course, there are some pockets within the brain as well. However, the general trend is that the gray matters on the outside, and the white matter is on the inside. All this business in here, that's all white matter. Now the organization in the spine is actually the opposite, whereas in the brain, the gray matters on the outside of the white matters on the inside, in the spine, which we're looking at here, this is the spine. You can see that the gray matter is actually found on the inside right, and the white matter is on the outside, and that's just a little pattern to take note of. It's not something that you need toe really stress about as being super important and related to a bunch of other stuff. Now, within the central nervous system, we often find bundles of axons traveling around together, and we call these tracks and make this distinction, because when we talk about bundled axons outside of the peripheral nervous system, we call them nerves. So you know, for our purposes, tracks nerves. Same difference. Really. We don't need to care too much about those distinctions, but I want to point out the difference in terminology. Now the brain and the spine are not actually solid masses. The brain has thes cavities called ventricles, and this is where the cerebrospinal fluid is produced. That's the fluid that actually bathes the brain and the spine. The spine itself, although you can't really see it in this picture, has a teeny little hole in it. And this is called the Central Canal. It's just a hollow tube that runs through the spine, so the the central nervous system is obviously an incredibly important structure. It is the command center of the body. As such, it kind of needs to be isolated. You know, you often get toxins, pathogens, all that bad stuff in your body, right? That's what your immune systems for. That's what your livers for. That's what your kidneys air for. Get that stuff out of there. However, the central nervous system is too important to be compromised, so it's actually gated from the rest of the body by what's known as the blood brain barrier. This is an end Athena Liam barrier that is composed of Astra sites, which are a type of glide all cell, and it's going to separate the extra cellular fluid of the central nervous system that is the fluid around the brain and spinal cord from the blood and you can see this right here. These cells are all Astra sites, and you can see that they are, uh, kind of like glue ping around this blood vessel. You can see the red blood cells right there. They're glue ping around it to create a barrier. So the blood brain barrier isn't so much like one wall in one location. It kind of is a structure that is very diffuse, but it's super important. And it's importance comes from the fact that the central nervous system has to be very, very carefully regulated. And we don't want toxins, pathogens, any of that stuff getting in, if it all possible now, the peripheral nervous system extends throughout the body, and it's made up of nerves which remember acts on bundles and ganglia, which are clusters of cell bodies outside of the brain and the spinal cord so similar to how in the brain, the cell bodies of neurons group together in the gray matter. Likewise, in the peripheral nervous system, you often see the cell bodies of neurons grouping together and sending their axons together as bundles. And you can see here everything in blue is part of the peripheral nervous system. The spine and the brain are kind of yellowish color. Uh, and all the other stuff is the peripheral nervous system on. You can see it's it's very diffuse. Network goes all throughout the body Now the other thing I want to point out is here We're looking at a section of the spine. Very similar Thio. This one right here. It's just not as good a picture. But what I want to point out to you is this ganglion. There are ganglia, riches, the plural of ganglion that run along the side of the spine. These air actually known as dorsal root ganglion. They're not the only gangly of the peripheral nervous system, but they're very important one, and I want to just point them out. And, of course, over here these are nerves that will connect to the spine, and you can see that there are a variety of ganglia and our ganglia there. So with that, let's go ahead and flip the page

The purpose of the peripheral nervous system is to gather information and relay commands from the central nervous system. So it's gonna bring information to the C. N s and bring commands from the CNS out to the body. Now the peripheral nervous system is often divided into ah, bunch of different categories. So, uh, one of the major divisions is between what's called the somatic nervous system and the autonomic nervous system. Now the somatic nervous system is usually are frequently referred to as the motor system because it controls voluntary movements. It has two divisions the Afrin division and the different division half as in to if, as in away. So a front nerves carry sensory information from sensory receptors to the central nervous system, whereas different nerves carry signals from the central nervous system out to the body. And here you can see the skin has these nerves connected to it. Those air part of the Afrin division, they'll go to the spine, which is part of the CNS, And there they might connect with an E for it nerve that's going to go and form a neuromuscular junction on muscle. So, uh, it doesn't always work out this way. The point is, there are two divisions. Some effort nerves, air going Thio have their signals go all the way to the brain. Others will simply stop in the spinal cord. Here. I just want to point out the, uh this is the primary, some out of sensory cortex. Basically, that's where all the sensory information from the body is going to come in and just want to show that this is connected to, you know, particular pathway and spine and that will, uh, go radiate, you know, down And of course, nerves will exit through the bodies. Just want to show you that you know these Ephron Afrin nerves, they're all over the body. It's not just a small little loop like this image implies. Now, the autonomic nervous system regulates unconscious functions. So the motor system is voluntary muscle movements, right? Uh, the autonomic nervous system can result in muscle movements. However, these air not conscious functions there involuntary and unconscious functions. And the autonomic nervous system is really going to control organs of the endocrine system, the cardiovascular system, digestive system and excretory system. All the systems that we don't really have conscious control over right now in and of itself, the autonomic nervous system can be broken between two divisions. The sympathetic division and the Paris Sympathetic division. Actually, there's another division to the enteric division. You don't need to worry about memorizing this, but it is becoming a hotter subject of research now that we're understanding the importance of our guts. And this enteric division is going to control the organs of the digestive tract as well as the pancreas and gall bladder. Uh, I only bring it up again because, you know, you know me, I love gut bacteria. I think the whole enteric system is super cool and cutting edge research, right? So let's get to the stuff that you need. Thio. Make sure, you know, and that is the sympathetic and parasympathetic division these air, often a simplified as the fighter flight division and the rest and digest division. Now this simplification is pretty much good enough for our purposes. However, when you try to dealt, or if you, I should say, delve into greater detail in these matters, you'll see why it's not a perfect definition for our purposes. It's good enough, so the sympathetic division is going to have neurons that release nor epinephrine. And remember, that's going to trigger that fight or flight response. That's why this is the fighter flight division. And you can see what happens in the sympathetic nervous system down here. You know, dilation of pupils, uh, dry, mouth inhibiting slide of production, increasing heart rate and all stuff that air getting you're ready. Bought your body ready toe. Either run away or fight. You know, uh, tiger, or whatever it is. Now the parasympathetic division releases a Siegel coleene, and this is going to be the rest and digest division, and it's going to have some effects that are opposite, but not always. I don't want you to try to think of these. Two things is sympathetic, Does this And parasympathetic does the opposite because they don't really line up quite so perfectly. So there are some contrasts. For example, parasympathetic division constricts the people's as opposed to the sympathetic dilating them, but and you know likewise, it reduces heart rate is supposed to raising heart rate. Of course, it has other kind of unrelated things. Um, and you know, you concede e all of its activities here, and the reason just to give a little preview. The reason you sort of say, it's not a great you know, the rest digest fight or flight? Uh, division isn't perfect. You know, For example, when you look at reproductive functions, uh, rest and digest well, stimulating the genitals just doesn't really sound like rest, huh? But that's a parasympathetic function, so, you know, these aren't perfect definitions, but for our purposes, it's a good enough generalization. So with that, let's go ahead and flip the page.

We've all experienced that moment of the doctor's office, where they tap our knee and our leg just shoots out completely in voluntarily. This is an example of a reflects. These are neural pathways that are going to control involuntary, instantaneous movements to some type of stimulus. Often you'll hear this referred to as a reflex arc. Now the sensory neurons will actually carry information from the stimulus into the dorsal side of the spine. So here we have the dorsal side. This is the ventral side me. Pop my head out of the way so you can see what I've written. Ventral dorsal basically think dorsal like the thin, which is on the back of dolphins. So the sensory neuron is going to carry information towards the spine, and it's going to enter the dorsal side, and its cell body will be part of that dorsal root ganglion. We talked about a little while ago, and it's either going Thio synapse directly on a motor neuron or a new Interneuron that will, in turn, synapse on a motor neuron. So basically some type of stimulus is going to, uh, signal it, and it's going to intern signal either The Interneuron or Motor Neuron. In this case, we have an Interneuron right here before the motor neuron, and it's essentially going thio downstream. Result in the motor neuron sending a signal to a muscle and causing some type of movement in response. So motor neurons will leave the ventral side of the spine, as you can see, and they'll synapse on a muscle right neuromuscular junction to create some type of movement. The basic outcome of all this is, uh, you know, a very fast response to a potentially damaging stimulus. This is your body's way of protecting itself. And what's important to note is that none of this involves the brain. It does go into the spine, so it does involve the central nervous system. But no processing occurs in the brain with these reflects arcs. So here, in our example, you can see this guy's touching a hot flame, which is not a good idea. Don't recommend it, and that's going to cause a reflex arc, which will result in him pulling his hand away from the flame very quickly. You know, this is like if you step on a sharp object, you just shoot your foot up before you even have a chance to realize what happened. And again, these reflex arcs are just very simple neural pathways that allow free, quick response to some type of stimulus, generally a stimulus that signals some type of potential damage or injury. So with that, let's flip the page.

Hello, everyone, In this lesson, we're going to be going over the major parts off the brain. Okay, so the brain is going to be in the central nervous system. Remember, the central nervous system is going to be the brain and the spinal cord. The peripheral nervous system is everything else. That's not the brain or the spinal cord, but it's still part of the nervous system. So things like spinal nerves and the nerves in your hands and things like that. But we're talking about the central nervous system. So we're talking about the brain and the spinal cord, and specifically we're going to go over the different regions of the brain that you are going to need to know. So obviously, the brain is the most famous organ in the human body, and you've probably seen diagrams like this before. But you may have not known exactly which portions of the brain you were looking at, so we're gonna talk about the forebrain, the midbrain and the hind brain. Now the forebrain is going to include things like the cerebral in the hypothalamus olfactory bulb. It's going to include some other things as well, which are a little bit more detailed that you'll learn more about later. Now the forebrain is going to be this region that you see here in orange and four means in front. And brain obviously means brain, and you may be thinking, but wait, that orange part isn't in the front of the brain, is it? Because this would be the front or the anterior side, and this would be the post cheerier or back side. So if we cut the brain in half, this is what it would look like from the side. View the lateral view. And this should be the front, this portion of your brain here. But you can see that the forebrain wraps all the way around to the post, either side. So you might be saying, Why is it called the forebrain if it's not in just the front? That is because the forebrain, whenever it was developing inside of the fetus, was actually in the front. And whenever you're developing as a fetus, your forebrain is going to be called your pro sin Cephalon, which I know sounds like a lot, and you guys probably don't have to know this information. I just wanted to let you know, um, why it's called the forebrain. That's because in the fetus, that particular region, the pro sense Cephalon that becomes the forebrain, is in the front of your head. And just for just so you guys know Cephalon or so phallic means brain. So whenever you see something like this so phallic, or you see that particular Cephalon so phallic those particular, um, letters in a word, it's generally going to be dealing with the brain. Now we're going to talk about the mid brain. This is going to be a portion off the brains dim, kind of like the upper portion of the brain stem that connects the forebrain to the hind brain, which you can see here in green. So there's going to be some very interesting structures in here, which we will talk about a little bit later. But basically it's connecting the brain stem to the fore brain, and it is going to be used for a whole bunch of different things. It's going to be utilized for eye. Movement is going to be utilized for processing visual information before it's sent to the occipital lobe. It's going to be utilized for coordination and your alertness and your midbrain is also going to have a particular name in development. And this is going to be the Mesen Cephalon, which I do not believe. You need to know this, but I just wanted to let you know that that is what it is called in the developing fetus. And again, you can see that Cephalon that so phallic word in their meaning, brain So your middle brain. Now I forgot to tell you all the different crazy functions that your forebrain can do. Your forebrain is gigantic. It is going to do so many different things. It is obviously the majority of your brain. As you can see there in orange, it's going to control your sleep. It's going to control your reproduction. You're eating your body temperature is going to control your motor functions, your emotional functions, and it's going to do a lot of your interpretation and thinking. Okay, All right. So now let's move on to the hind brain, which is gonna be more composed of the brain stem. But it's going to include theme medulla, oblon gotta ponds and Sarah Bellum, and it's going to be the lower portion of the brain stem. This is a very important portion of your brain because it connects your brain to the rest of your body. This is going to connect your brain to your spinal cord, and you can see your hind brain is here in pink and is going to connect to the spinal cord, which is going to be more inferior so more below the brain. Now your hind brain also has a particular name during development. Its name is kind of funky. Its name is Rahmbo, Aram Ben Cephalon, and again you can see the Catholic word in their meaning. Brain. Okay, now it's going to do, Ah, whole bunch of things. Most of your cranial nerves are going to come off of your hind brain. It's going to control some eye movement as well. Your facial sensations, Your balance. Ah, lot of your voluntary movement is going to be, um, controlled through your hind brain. It's also going to control your heart rate, your blood pressure reflexes, your breathing, things like that. Okay, so now let's go down and let's talk about a more specific region of the brain called the cerebral. Your cerebral is going to be in your four brain. This is the largest portion of your brain and probably the most famous portion of your brain. Now, this is a large outer part of the brain that is going to include the cortex. The cortex is going thio surround the cerebral, um, and other sub cortical structures like the hippocampus. I So your cerebral, Um, whenever you think of what a brain looks like, you're looking at the cerebral. This is gonna be 85% of your brain, and it is divided into two hemispheres, a left and a right hemisphere, and it's gonna have all sorts of different things inside of it that are going to do different functions. Your cerebral is very famous for your thinking. You're planning your reasoning skills, your interpretation, off information and senses. And it's also very important for language. So this portion of your brain is basically what makes you intelligent. For the most part, it's the thinking part of your brain. Okay, So, like I already said, it is going to be divided into two hemispheres left and a right, but it's gonna be connected. We can't have those two hemispheres not talk to each other. they need to communicate with one another, and they're going to utilize the corpus callosum. This is going to be a bundle of nerve fibers called axons, that transmit information between the hemispheres. This is very important. This allows the left side of your brain to talk to the right side of your brain. And in fact, the left and right sides of your brain do have slightly different functions, so they do need to communicate with one another, so it's very, very important. Now the cerebral cortex is going to be the outer layer of the cerebral, composed of gray matter. This is gonna be the outermost layer of the brain. Most likely you're going to see whenever you think of a brain. Now I want to show you a picture. Let me get out of the way here. I'm going to scroll down a little bit. Do you see this arrow right here? It's going to be pointing to the corpus callosum, which is going to kind of be right here, which is going to allow those two hemispheres of your brain, your left and right hemispheres of your brain to connect with one another and to communicate with one another so that they can share information. So that's a good visual representation off your corpus callosum. Okay, so now the cerebral, um, is quite large, right? It's 85% of your brain. It's going to be chopped up into four different lobes. So each side, the left and the right are going to have a frontal lobe, a parietal lobe, the temporal lobe and an occipital lobe that are all going to have unique functions. The frontal lobe contains areas involved in decision making and your primary motor cortex. So this is gonna be the cognizant part of your brain that's actively making those decisions. The parietal lobe is involved in sensory information processing, and it contains the primary somatic sensory cortex. Okay, so the parietal lobe, whenever you touch something, it is actually looking through all the sensory information in processing the sensory information. Whether that site taste, smell, touch anything like that, your parietal lobe is taking care of that. Okay, Then we have our temporal lobe, which is going to contain the regions involved in hearing and language and visual processing. So whenever you're listening to language or you're speaking your temporal lobe is going to be involved in that process. Now, finally, we have the occipital lobe, which is the visual cortex. This is where the majority of your visual information is going to be processed and understood. So it's utilized and processing visual information. Now, if I scroll down, you can actually see these different lobes that we talked about. Here we have the frontal lobe, which is going to be here in this kind of brownish color, and you can see that there's also the Samata mo se mato motor cortex, your Samata motor cortex or your primary motor cortex. Same thing. Just two different names is going to be what plans and executes your bodily movements. I'm using it a lot right now when you're running around or you're doing something, you're using your primary motor cortex to do those motions. Now we also have the tomato sensory cortex, which is going to integrate sensory information from the body, and it's going to combine all the sensory information to put together a picture of what's happening. Okay, and then we have the parietal lobe, which you can see here in this purple color. And remember, the parietal lobe is also utilized in that sensory information. And it's going toe hold the somatic sensory cortex. So these two are going to be together. Okay. And then we have our occipital lobe in green, which is going to be utilized for your visual information and processing. And then we're going to have the temporal lobe here in blue, which is going to be used for language and auditory information. Okay, everyone, that's all I have for this particular section on the brain. Just remember, the brain is going to be part of the central nervous system, and it is going toe have a forebrain, midbrain and hind brain. And the cerebral is going to be the largest part of the brain, 85% of the brain. And it's going to have these different lobes that have different, unique functions. Okay, everyone, let's go on to our next topic.

with lobes of the brain. We saw that different cognitive processes will be located in different areas. However, sometimes there are differences in cognitive processes across the hemispheres, for example, language tends to be left hemisphere dominant. Most of the areas involved in language processing will be found in the Left Hemisphere and there are very few in the right now. Uhh these, uh, differences between the hemispheres we refer to as lateral ization. And just as an example, we're gonna look at two areas in the brain Broca's area and Vennochi's area. Broca's area is involved in speech production and is found here in the frontal lobe, whereas Veronica's area is part of the temporal lobe and is involved in language comprehension. And these black lines are actually trying to indicate that these two areas air intimately connected. Aziz, I'm sure you can imagine the production of speech and the ability to understand what's being spoken to you are going to be linked processes. However, the take away I want you, uh, to get here is just that different functions are localized to different specialized areas of the brain and that there is not always going to be balance between the right and left hemispheres. However, I will dispel the whole right left hemisphere nonsense that you find in pop science right now. That's all garbage. Don't listen to any of that. Just know that there are differences in the cognitive processes between the hemispheres. However, they're not nearly as pronounced as pop science will have you believe. Now, another way to look at the cerebral cortex is to divide it between sensory motor and association areas. Essentially, in this model, we think of sensory areas as receiving process and processing sensory information. These will be areas like the visual auditory and somatic sensory cortex is that's the plural of cortex and you will find them in and around thes regions of the brain here in pink. Now, the motor areas process voluntary motor movements and these air going thio be processed in the primary motor cortex, which, you can see has been highlighted in green for us right here, and notice that it's parallel to the primary somatic sensory cortex right here in dark pink. And hopefully it comes as no surprise that the area that receives information from the body would need to be intimately connected with the area that sends signals back to the body for movements now basically, the rest of the brain. That is not, You know, a sensory area or motor motor area is considered an association area, and these association areas are basically there to extract meaning from the sensory information we receive. Uh, to some of you, this might come as no surprise to others. This will be kind of a ground breaking idea, but what you perceive as the world is not rial. It's just a construct in your brain, so things you are seeing you're not really seeing your brain is interpreting the signals from photons bouncing off of it to construct a new image of it. So essentially these association areas are there to take what comes from the sensory areas and make sense of it and generate your reality. Now with that, let's flip the page

the Diane Cephalon is the part of the forebrain worth noting because it contains the thalamus and the hypothalamus. These structures are super important, and they're actually kind of small when you look at them in the grand scheme of the brain. Here we have a zoomed in picture and you can see the thalamus sits above the hypothalamus, and that's where it gets its name. Hypo means, you know, lower. So it's just below the thalamus. Now the thalamus basically acts as a relay center for the brain. I like to think of it as, AH, telephone operator in a way information sent in and then it routes it to the appropriate area of the cortex. Now it's gonna play an especially important role in visual processing, routing the different types of visual information to their appropriate areas for processing. Now the hypothalamus is important because it's going to serve is the link between the nervous system and the endocrine system. And it's going to do this by interacting with the pituitary gland, which is an endocrine gland that is going to have very sort of high level effects in the endocrine system, high level signaling now the hypothalamus is also going to be involved in home. You know, Stasis, which is why it makes sense that it will serve as a bridge between the two major communication systems in the body is home uses requires lots and lots of really good communication. Now, the limbic system is kind of a loose definition that more or less encompasses ah bunch of different structures, mostly in the forebrain. There's some structures in the midbrain that are referred to as limbic midbrain structures. We don't really need to worry too much about these for the, uh, the most part the structures of the limbic system or in the forebrain and the only ones that we need Thio actually know about our all located in the forebrain. Now, these air actually structures that they're going to be kind of a deeper in the brain, so they're not at the surface. There, below the cortex and thes structures are the hyper earth. I was gonna say hypothalamus, hippocampus and the amygdala. Now the hippocampus is going to be involved in learning and memory, and it's actually especially important for the formacion of long term memory and spatial memory. Now, long term memory. You're gonna be memories that you can, you know, recall for a long time. For example, you know what your home when you were a child looked like or something to that effect. Now, without the hippocampus, people are actually completely incapable of forming these types of long term memories. So there's a famous example of a person who had both of their hip, A camp I removed. And they were completely unable to form memories for the rest of their life. People that they met after this operation, they were never able to recognize no matter how much time they spent with them. It's also involved in spatial memory formation, and this is sort of like your ability to construct mental maps. So, for example, when you go to a new part of a city or something and you don't know your way around, you actually have to build kind of a mental map with lay out of the area and and it's gonna be the hippocampus that's responsible for that process. So, generally speaking, learning and memory, specifically long term memory and this type of spatial memory. Now the amygdala is involved in emotional processing, and it's actually going to kind of sit right on the end of the hippocampus. So we have the amygdala here, and this structure is the hippocampus. So it sits right at the end of the hippocampus. And it's going to be linked in some ways to the hippocampus, because emotions can create very powerful memories. There's a strong link there. Uh, you know, I I don't want Thio make too many wild assert ations, but there's certainly a link between the emotional processing of the amygdala and long term memory formation. Now, with that, let's actually go ahead and turn the page.

the cerebellum, or little brain, as its name means, sits in the back of the brain stem underneath the cerebral. Um, and as you can see, it really does look like a small version of the cerebral. Hence its name. Now, its main job is gonna be integrating motor functions, and it's not gonna actually initiate any sort of motor movement on its own. It's actually going to coordinate those signals and integrate the output. So, for example, when you're standing up straight, you actually have to coordinate many different muscles all over your body to maintain your posture. And without the cerebellum, you basically just face plant. You wouldn't be able to do that. It also plays a role in fine motor movements, for example, doing delicate tasks with your fingers. Um, now, moving on the brain stem is going to contain the pons and the medulla. Ah, blonde guidance right next to the cerebellum. However, our image here laksa, cerebellum. I don't know why Bias maybe wants to really emphasize the brain stem. Now, the Pons and the medulla oblon gotta are gonna have a role in unconscious types of functions that are necessary to live often. These are structures. Kind of thought of is like the lizard brain or something like that, very basil functions that are actually absolutely necessary to life. These air, very important areas. I mean, the ponds is involved in swallowing breathing, eye movements, posture and very interestingly dream production, which is not well understood it all. I mean, sleep and dreaming remain a big mystery in science to this day, but it is known that the ponds has a very important role in producing dreams. Now, the medulla problem got also kind of takes care of a lot of those passive unconscious functions that are necessary life, including maintaining heart rate. Uh, it's also gonna play a role in breathing in addition to the ponds, and it also is going to have a role in blood pressure. So that's why these air, you know, sometimes thought of as, uh, you know, more basil structures. They kind of take care of those unconscious functions. So with that, let's actually go ahead and flip the page

our brains have an amazing ability to reorganize themselves. We call this ability narrow plasticity, and this is when our neurons reorganize themselves by modifying and forming new connections. Now this is, uh, related thio synaptic plasticity, which is the ability of neurons to strengthen or weaken their connections based on various activity patterns. And you can see a very simplified version of that here, where we have one neuron that receive stimulation that's going thio have some change occurring at synapse and another neuron that does not receive stimulation and does not change its synapse. So synaptic plasticity is sort of a mechanism that contributes to neuro plasticity. Now, one amazing example of neuro plasticity can be seen here with something known as phantom limb syndrome with phantom limb syndrome. Basically, people who have lost a limb, um, will still experience the presence of the limb there. And that's because even though they lost the limb very suddenly, their neural networks haven't adapted yet to that change. So one amazing way that people deal with phantom limb syndrome is by using something called a mirror box. So it's very common for people with phantom limb syndrome to feel as though, Uh, the limb they've lost is, like, tensed up and and uncomfortable. So one way they deal with this is by using a mirror box, and they'll have the person, uh, you know, essentially use the hand or, you know, the limb that they still have in the mirror box, and it will appear to them as if it's the limb that they're missing the phantom limb and so they can take that limb in the mirror box and they can e. They could, like, tense it up and then ease the tension and relax it. And it will appear like it's the phantom limb doing that, and that will actually help change their neural networks. Thio get rid of that discomfort. So pretty amazing stuff. Neural plasticity. Also, people with traumatic brain injuries are capable of, you know, recovering lost functions due to brain damage by reorganizing other parts of their brain to pick up the slack and carry out those functions that they're not even supposed to do. Technically, it's pretty incredible, and this, you know, this capacity is much greater when we're younger and we sort of lose it as we get older, which is why you know, Children are so much better able to recover from brain injuries, for example, and also better able to learn things. Now, Nure O Genesis is the growth of new nervous tissue. And this occurs mostly when we're developing embryos as adults, we really can't produce new nervous tissue. However, there are some small exceptions Now, all of this narrow plasticity synaptic plasticity is ah highly, um, related to you learning and memory. Now learning is going to be, uh, technically acquiring, modifying or reinforcing some type of knowledge, behavior or skill. So, uh, you know, you can, uh, for example, learn a new skill, and then you're going to be adapting your brain to that new skill. Or you can have, you know, a neural network that's already in place for some particular behavior, for example, and and reinforce that make it stronger, strengthen that behavior, so to speak. Memory, on the other hand, is going to be the encoding storage and retrieval of information. There's actually different types of memory. We actually have what's known as sensory memory, and this is a very transient type of memory. It's basically, uh, the ability to hold sensory information for just like a second after you perceive it. So, for example, if you look at something and then very quickly, close your eyes for a second you hold that image in your mind is if you're still looking at it, it's It's that sensory memory of what you were just experiencing thebe perception that you just had. Now there's also short term memory, which is this ability to recall a small number of items without actually having to sort of, like, rehearse it. Technically, rehearsal is jargon term and is, you know when. For example, if you're trying to memorize something, you repeat it over and over and over to yourself, just kind of strength in it in your mind. So short term memory is our ability to, you know, kind of without having to really try to remember things hold just a few limited pieces of information in our mind. In fact, it's thought to be about, um, seven pieces of information, and that's why telephone numbers are seven digits long. So there you go now, long term memory is going to be information and knowledge that's stored and recalled for a very long time. In fact, it could be potentially your entire life that you can retrieve this information and the mechanism behind this. Um, you know, long term formation of memory is thought to be something called long term potential ation. And this is the long term strengthening of a synapse based on activity patterns. And it's, you know, this is thought to be its its extrapolated to be involved in the cellular mechanisms behind learning and memory. Essentially, you know, we're not I'm not trying to sit here and tell you that, uh, all memory comes from long term potentially ation, but there's definitely some involvement of this process in long term memory. So what happens with long term potentially ation? Well, essentially, uh, you know, let's take our example. Synapse. Now, due to some type of activity pattern, this connection is going to be strengthened. And one of the ways it will be strengthened is by adding new receptors to the post synaptic, post synaptic side of the synapse. And you can see that here we only have two receptors. Whereas over on this side here, we now have four receptors. So that's going to strengthen that synapse, right? Another thing that can happen is by releasing Mawr neuro transmitter, we will strengthen that connection. See, here we're only releasing a little bit of neuro transmitter here. We're releasing a lot more neuro transmitter. So these two effects are gonna add together and result in a much stronger connection at this synapse by a combination of added receptors and added neurotransmitter. So those two, uh, those sort of two facets air going to combined together and produce a much stronger overall response with that, let's go ahead and turn the page.