Brain and Behavior - Neurons and Glia

okay what don't we get started so um couple of announcements before we get started um I told you about the weekly exercise classes that I lead I just want to say that we're doing a big kickoff event this Sunday this is the second uh uh Sunday class that that uh we're we're um that we've done and this is a big kickoff event for our empowering women in science uh Explorations floor both men and women are um certainly invited it's going to be uh a workout but the cool thing is that we're going to have live drummers there so if you want to come and and uh um uh experience the workout this is a really good week to come Sunday from 1:30 to 2:30 you could also sign up for the um uh kind of leadership training uh overview that we're going to be doing afterwards and um I'm just going to leave this up here at the at the front so if you're interested sign up tell me whether which uh um components you're interested in you can come to to the workout only you can come to the um leadership training only or you can come to both um let's see uh is everybody getting all the the uh lectures and the questions off of Blackboard okay is that working yes okay okay I could I could convert those to uh PDF files okay great any any other problems okay so definitely um definitely uh download all those all those um uh files and uh all the questions and all the information that's that's been put up there um okay oh and then this week is your first week um of lab sessions so uh on uh tomorrow and Friday will be your first lab sessions and you will be uh taking lab with Eric over here whose lab sessions are uh Thursday at 3 and 5 Thursday at 3 and 5 Helena up there whose lab sessions are sorry on Friday on Friday helenette wave over there and then Sarah 11 and one on on Thursday okay great so first session go there we're going to be talking about scientific method it's going to be a really fun fun lab so that will be uh uh this week so what I wanted to do is um hear from you a little bit uh in the beginning of this class and specifically I wanted to ask you guys the question why did you decide to take this class what is interesting to you about Neuroscience um and it could be from something you've been interested in in the past or it could be something you became interested in in the first couple of lectures but I'd really like to know so what i' like to do is split up into groups of about five just naturally go and and find about five different people and talk about this amongst yourselves for about three minutes and I want to kind of hear from from you guys about what interests you uh in Neuroscience kind of at the beginning of this class okay so please just just uh uh introduce yourselves to five people around and and um tell each other uh why you took this class is it OD see I just forgot the 9 and 11 okay okay okay everybody should be talking or listening right now okay okay it looks like you guys conveyed your information who wants to share so give me some some reasons why you took this class in the back you okay great she what okay any any other reason you chose this class I see Psychology major so you're interested in Neuroscience great okay anybody have like a a uh um thing that they became interested in in Neuroscience that made them want to learn a little bit more about Neuroscience yes um I uhuh great great so got interested in Neuroscience through her course uh perception and sensation is that yeah so um that's great any anybody else unique reasons how about you yes oh well um I do it sence okay need it for your natural science requirement s resarch primate psychology okay primate psychology yes that's a topic that's really interested me um on my last sabatical which was almost seven years ago now um I had the privilege of going to batswana to study uh baboons in the wild to look to see exactly you know what are they doing out in the well what kinds of things are they learning what kinds of things are they remembering and that was a fascinating uh um a fascinating uh experience um they are not doing uh um what you might think they're doing from the tests that are typically done in Laboratories which is exactly why I went out there um they they but not that they're doing nothing they are so focused on social interactions they are primates just like us and they are interested in um who's dominant to who who is going to be nice to me and who is going to beat me up and take my food away and that is what they focus their their cognitive attention on and because of that kind of the task that I've uh developed in my lab to test primates uh focus on memory for those kinds of social interactions so yeah that's uh topic very interesting to me as well anybody else yes yeah okay great interested in music and the brain and Alzheimer's disease and how um music can set off uh um lots of different reactions um one of the most interesting um uh fields of study is the neurobiology of music and that is really centered at University of Montreal and McGill University up up in Montreal and uh research up researchers up there including um Robert zor have have done a lot a lot of work looking at functional magnetic resonance imaging do you guys know what functional magnetic resonance imaging is yes no yes okay so functional magnetic resonance imaging is using an MRI magnet everybody knows what an MRI magnet is you usually go in there if you have a knee problem or you can image different parts of the body including the brain but functional magnetic resonance M functional MRI is where you can go in and actually look at um uh an indirect measure of brain activity and so you can put somebody in the magnet and and um deduce which part of the brain is is active as they're listening to music and I love the study that uh Robert zor did on um those pieces of music that kind of give you Goosebumps so what what the evocative power of music and what part parts of the brain are being stimulated when you hear that piece of music which is different from for everybody some people don't have any pieces of music that will give them kind of Goosebumps because it's so evocative but some of us have lots of different kinds of music so he found that piece of music for each person and there are specific brain areas including areas involved in emotional processing that we're going to be talking about including the migdala that uh get activated in these kinds of processes so it's a new area but but very very fascinating we're going to talk a little bit about that um in both the auditory part of the class as well as the emotion part of the class anybody else yes dreams yeahor as like smell yeah and what's going on yeah yeah so he's interested in sleep and dreams and how smell evokes memory and um the evocation of memory by smell is fascinating because um we won't go over this in great detail but um we will talk about the major senses like vision and audition and smata Sensation that have specific Pathways into the cerebral cortex they go through the brain stem they go into the thalamus and then they go into the cortex that is the prototypical sensory pathway into the brain however Alf faction is different Alf faction has a direct route directly into the brain does not um go into the thalamus and one of the areas that it goes into is um an area that is a major feeder to the hippocampus the area that we um that we talked about is important for long-term memory which is why uh smell can be so evocative for our long-term memories sleep is very fascinating as well um a researcher at uh UC Berkeley has uh started kind of uh revivified the the study of sleep and memory and and showed that even small naps can significantly improve both your um procedural memory your ability to um do kind of motor learning tasks as well as your episodic memory your hippoc cample dependent memory so um it's uh uh there maybe a reason why you get that lull and that sleep uh uh desire for sleep in the afternoon you might need something that extra boost to improve your memory and we certainly know that if you um I'm always I I always uh you know I I teach this uh regularly but it is striking to me that if you deprive um in an experimental animal situation if you deprive a rodent of sleep do you know what happens they die sleep is a basic physiological need it's not like oh if I have time I'll sleep you have to sleep and not only do you have to sleep but it's doing good stuff it's it's extra naps and and uh if you enhance certain um uh uh stages of sleep you can enhance certain forms of memory and that's exactly what's what's being studied right now so yeah very interesting topic one more anybody else question or interest yes Deja Vu okay interested in deja vu so um that is uh a very interesting uh hasn't been studied a lot directly at least the Neuroscience of it I think the psychology of of dja Vu has been studied studied more uh but certainly what we know is that it it involves the um um um retrieval of uh memory and that involves the hippocampus um you'll will learn that um while there's there's weeks and weeks and weeks of information to learn about Neuroscience we're still at some levels at a very basic level of understanding so you think oh well we can understand T sha Vu and we can understand how sleep and and we have little Snippets into that so that's one of the things I want to impress upon you we know an enormous amount but there's also an enormous amount that we have to learn and so um trying to separate out uh where we are very very on very strong ground in what we know and where we're um kind of uh uh still uh searching and um um asking the experimental questions okay great so why don't we get started with the main lecture today's lecture focuses on neurons and glea the main building blocks of the brain so as I mentioned I believe in the first lecture the entire human brain the cortex the cerebellum brain stem the entire Central and peripheral nervous system are made up of Simply two types of neurons of cells neurons major brain cells that we consider the workhorses of the brain uh and and Gia cells there are fewer categories of glea and um I have to say that I think in the next 10 years it's going to be the next 10 years of Gia cells and really understanding and appreciating what these Gia cells do we're going to uh go a little bit into what we know but actually that is a very very exciting area of research we've ignored them for many many years because there's so many fascinating things that neurons do so we're going to really focus the whole course on neurons but uh just know that glea I think are unsung heroes uh in the uh um in this kind of uh uh um uh two two-stage uh um um cell uh cell makeup of the brain okay so all neurons and Gia are basic cells from basic biology all cells have have similar uh makeup they all have a cell membrane they all have a cell body they have nuclear membrane that is a membrane around the nucleus a nucleus with DNA that has the codes all the proteins that are made by the cell they have mitochondria the uh kind of uh the PowerHouse of the cell and ribosomes which are structures that help uh in the production of proteins so all cells in the body including neurons and glea have all of these characteristics in common so all neurons are are similar in these ways to liver cells or colon cells or stomach lining cells but what we want to focus on today is what's so special about neurons in particular here I'm specific about neurons not as much about Gia what's special about the neurons one is they have very unique morphology so neurons have a cell body like all other cells but they have two major specializations one are dendrites which are the input structures of the cell and the second specialization is the axon the output structure of the cell okay the second major specialization of the neuron is the way they communicate liver cells just sit there they do their job in in processing uh different uh um food groups that you bring in neurons are special because they communicate with with a combination of electrical and chemical synapses and that communication ability is the basis of how we're able to see hear perceive remember think and and uh kind of the basis of our personality so we're going to be focusing on the next two lectures on electrical and chemical synapses but today we're going to focus on the basic building block so what makes neurons unique okay so to understand certainly our our our understanding of the neuron we need to go back in history and uh go back to these two figures that I mentioned in the very first lecture ramoni kahal Santiago Ramon kahal a Spanish neuroscientist that's considered the father of modern neuroscience and Camilo GOI an Italian um early neuroscientist um in 1906 both of these two scientists together were awarded the Nobel Prize for um one the discovery of the goldi staining technique that we talked about and two um his use of the GOI staining technique to really distill out some principles of organization that we now know are completely true uh way back in in the late 1800s okay so um ronal was a very very interesting character and for those of you interested in history I would highly recommend this book Recollections of my life it is an autobiography written and recently republished um of the life of Santiago Ramon kahal um it's great that we have this record of his um of his life uh because without that we have just pictures um I love this picture because it conveys the joy of Parenthood doesn't it just the joy look at that if we only have this picture we might have certain um ideas about Ramon cahal it turns out he was a very devoted parent he had six kids and he loved his children even though he doesn't show it very very generously in the in the photos um you will not be surprised to hear after we go through a few more of these slides that he started out with aspirations to be an artist and he might have been one of the greatest um Spanish artists but his father said that is just not serious enough you have to do medicine so because of his father he went into medicine and what he did is combined um both his amazing artistic abilities with what turned out to be an amazing scientific mind as well and that that allowed us and allowed him to make some of the first major um uh discoveries in neuroscience and neuroanatomical organization of the brain okay that's ramonica Hall Camilo GOI was uh a phys physician a doctor a professor in um um in Italy um I love the title that he had um he his title was extraordinary professor of histology like I wish NYU would give that title extraordinary professor of Neuroscience no I'm just Professor but he was extraordinary professor of histology um at the University of Pavia and he was known as an amazing teacher of scientists so his lab was open scientists came to learn how to do the craft of experimental design in his lab um in addition to his his development of this gold staining technique which he was most famous for he was also had his kind of irons in lots of different fires um making major discoveries about malaria and differentiating different forms of malaria and showing the different stages of malaria through um histological examination um the focus of his time was the nervous nervous system right at the end of the 1800s early 1900s people were very interested in the nervous system so he jumped into science interested in that um still got into uh uh malaria research uh was a great teacher but again he was the one that discovered um how to stain the brain so that you can look at individual brain cells now I told you um uh what this goldi stain was and I showed you drawings of the goldi stain here are two pictures of what the goldi stain really looks like we use it today you can buy a kit for the fast goldi technique today based on the original technique that goldi goldi used of course it's all uh um um uh made very easy to do um but here you can see a cell body of a neuron and lots of these dendrites coming out and here you see some of the extra staining of other cells that can um kind of engulf a particular brain area and make it completely black if it stains all of the brain tissue in that area here's another nice example of a what's called a paramal shaped neuron and we see the dendrites coming out here this is probably the thinner uh um structure right here is probably the axon but you can see that in this section we had random staining again random we can't tell which brain areas in this chunk of tissue or this chunk of tissue is going to be um revealed and it's a little bit luck of the draw and you just have to stain and stain and stain but this is exactly what it looks like little bit messy but um it was uh the the both the scientific mind and the Artistry of both uh um Gogi and kahal that um made those drawings that we talked about uh that we saw in the first lecture now it's fine to make the drawings but what is the organiz ation of this brain structure we know what the organization of the liver was the heart how are these brain areas organized and this is where goldi and kahal ended up in a huge fight in fact they were barely they were not speaking to each other when they came and gave their uh Nobel lectures and gave their lectures on two very very different opposing topics um goldi um was a champion of What's called the neuron Doctrine um kahal said that uh so this Doctrine states that neurons are independent functional and physiological units in the brain so that each one of these neurons are independent neurons uh independent units like an independent um liver cell is independent from each other liver cell goldi looking at the same material stained by his own technique looked at the material and he said wait a second I support what they call the reticular Theory reticular theory states that all neurons are linked to one another by an asmosis which is which means a continuity so yeah there are these uh um long processes here but they definitely saw that the processes are meeting each other they couldn't see exactly whether they were continuous or they were separate it was just beyond the resolution of the microscopes at that time and GOI reasoned that this is brain tissue we know that this is a tissue that is um processing our highest level of intelligence and cognition and perception and so what um um um it makes more sense if there is perhaps a slightly different organization from other boring structures like the liver that doesn't have to do much computation um and he thought that by uh having more continuous integration you would have more power to compute okay GOI said sorry kahal said no this is a basic unit the cell theory extension of the cell theory says that each cell is independent this is no different from the brain and um I believe even though he couldn't see it for sure that these individual neurons are independent units okay so as I said um we couldn't they couldn't resolve this question um back then in the late 1800s early 1900s and in fact if we only had the light microscope even the most powerful light microscopes we have today still couldn't resolve it because um in fact the technology uh for the light microscope has been unchanged for over 150 years and the absolute limit is about a thousand times which is simply not high enough to resolve what exactly is happening at the connection from uh the axon of one neuron to uh well the axon to the dendrite is it continuous or is it not continuous that was the big that was the big question um so here are some examples of Cal's drawings of Gogi stained material so you can appreciate his artistic um um abilities uh again he never saw this beautiful picture he saw individual uh stained cells and he put them together with where they were in the in the ction relative to the top of the cell and just a accurate drawing of what the different uh branches look like here's a drawing of the hippocampus a rodent hippocampus showing um uh the different types of neurons and here also he's showing these as individual units and he's showing the flow of information he had no idea which flow of information he wasn't recording in these cells he was just looking at these pictures but um through this look he um uh this this study of all the different brain structures he gleaned um so this is the sellum and here is an individual cell from the cerebellum um he gleaned two major principles that you need to know um one is the law of dynamic polarization we mentioned this in the very first lecture the law of dynamic polarization states that information flow flows in a predictable and consistent Direction within each nerve cell from the dendrites many more dendrites in general in in neurons through the cell body and down to the axon if you remember we talked about this beautiful drawing Again by cahal of the retina and it's you can start to see his his um logic of thinking here the retina we know is a structure important for vision and um he noticed that the um dendrites tended to be shorter and the axons were the ones flowing out of the retina V the eye is made to bring sensory information into the brain given that all the cells were facing in the same direction and these cells were modifications of the cells that you see in the cerebral cortex he reasoned that um all these cells always have a specific flow of information from the dendrites to the axons again no physiological evidence just from Anatomy second principle principle of connectional specificity and this is a principle that really just flies in the face of G's um reticular Theory here in kajal's principle of connectional specificity he says there's no cytoplasmic continuity between the nerve cells in other words goldi was wrong nerve cells do not form random networks he said that that an inefficient way to be able to process information instead given the uh beauty that he was seing and specificity of the different brain types and the uh uh flow of information he said that each cell forms specific and precise connections making contact with only some nerve cells and not with others he couldn't be sure about this but again he gleaned this from his study of um the basic uh uh many different brain areas and it turns out that all of these principles were correct um in the uh in the um in in the forward of this book a very famous neuron anatomist um max Cowan um makes the comment that uh all the neuron anatomists that came after cahal would get really worried if they found something that was different from what he had put in his major uh uh papers and books that he published over the years even though they were published so long ago basically we're using similar uh techniques I talked to you about brainbow and and the gfp uh approaches but but you're still looking at anatomy and um um max Cowen makes makes the comment that neur anatomists if they happen to find something that seemed to disagree with gahal got very very nervous because he was almost never wrong so you want to make sure you're seen something and you kind of neur anatomists even today will go back and double check to see whether it's consistent with some of Cal's early um early observations of course he didn't use everything and there are certain techniques that kahal just wasn't able to look at at all but he had that level of precision in his um in his analysis okay so so back in um uh uh when kahal and um goldi won the Nobel Prize this debate was still raging I have to say that that the descriptions of the time said say that kahal was winning um that more scientists believe that the neurons were individual units but again nobody could tell the difference and the question is how was this debate resolve okay we're back in 1907 in in the Nobel prize winning winning year it wasn't resolved until the 1950s with the Advent of the electron microscope the electron microscope is a microscope that allows you to go down to a much much lower sorry higher level of resolution um in brain tissue and look to see between the axon of one neuron and the dendrite of the other is that a continuous um um um flow or is there a space that is on the nanometer scale of um uh resolution and this just shows uh uh the axon a uh perhaps more detailed uh view of the axon connecting of this neuron connecting to the dendrite of the next neuron and here is uh an electron mic microscopic picture Em picture of a synapse this is at a resolution of 0.2 nanometers so what this is doing is taking let's say this is a synapse right here okay we are um taking a section through the axon and the dendrite and looking at the cross-section in in this picture right here here is the dendrite on the dendrite was called a little spine it's like a little mushroom out onto the surface and onto these spines axons terminate a is axon terminal and what you can see um um in a fuzzy way is these little circles these little circles are uh synoptic vesicles they're filled with neurotransmitters uh ready to release at the ax terminal we're going to be focusing on that in two lectures from now but for this one for the structural lecture the key point is this space right here there is a blank space here is a membrane it's the end of the axon terminal and there is a space right here between the axon terminal and the um dendrite the dendritic spine right here again it took about 50 years for us to get this resolution to0 2 NM be able to show definitively that there are separations physical separations between one neuron and the next okay more details on neurons and glea this comes from your book um again just nicer pictures of um the different major components of neurons here is a picture of the cell body with the dendrites uh coming out around you'll notice there's lots and lots of dendroides typically only one axon coming out typically it's much thinner than the dendrites another important component of the neuron is called the axon hilock the axon hilock is right here right as the cell body turns into the axon this is a very very important location in the cell in terms of integrating input and it decides whether the cell is going to fire Action potentials down the axon or not we're going to talk more about the axon H but for this lecture I just want you to know where it is on the cell the axon hilock is located um just where the cell body turns into the axon okay the output structure dendr as I said receive input signals you can see it has a huge space onto which uh um inputs can can be uh um uh deposited onto the cell and one long axon then that terminates in particular locations there's one axon but there can be many uh branches at this level so it it's not like one cell body only um um uh contacts one other uh neuron it can contact many hundreds of neurons um and this output is transmitted to other sides and importantly as uh kahal first deduced from his anatomical drawings there is a specific unidirectional and um nonb backward going direction of information flow from the dendrites down to the axle okay what are some unique components of the neurons we talked about dendrites the input zones they receive inputs from more than hundreds of other neurons and um they they uh there are many dendrites per cell axons carries the output usually there's one axon and it transports the axons are are are transporting chemicals from the cell body to the terminals um it transmits electrical impulses that's going to be the focus of uh m day's lecture to the terminals and the speed of that transmission determines is determined by size by milein we talked about what makes uh the white matter white it's myin it's a fatty uh coating of insulation and sends outputs to again lots of different um lots of different uh uh other neurons this is a table from your book uh you should know all these distinctions um the differences in number many many individual dendroid usually one major axon with lots of terminal branches off of one major axon um this is uh um uh dendrites uh taper progressively towards the end so they're very thick when they're near the cell body and get very very thin and axons are uniform uh distance they are thinner than the thickest part of the dendrites um axon hilock uh is in the axon it's not in in the dend um uh covering or sheathing um it's axons are usually not but not always covered with myON we'll talk about why that is the case and what that means in terms of what the axon what that neuron would be able to do when it's either covered with myelin not covered with myelin dendrites never have myelin on them length um uh axons could be really really short to several meters long and Ds are usually much shorter than axons as we talked about in that drawing of the retina from kahal um branching axons uh usually Branch along the length and branches tend to be perpendicular uh to the main branch and dendrites uh Branch along the length and branches occur over wide range of of um area Okay so let's talk about the range of different sizes and lengths of neurons across the animal kingdom flies have nervous systems they have neurons and they work really well how many of you have not been able to catch a darn fly when he's buzzing around your head yes okay it's really annoying his neurons can work faster than yours and we have this all the way compared to the giraffe example that I talked about where the his um motor cortex neurons are going all the way down to get all the way down to move his little hoof okay so a a wide range and and it's really amazing to think about how how widely the the um size of these neurons differ across nature I love this picture from the book I I recommend that you go go and study it um uh just to appreciate uh the different sizes all these neurons are drawn to the same scale where um this uh um scale bar is 200 um micrometers micrometers and you can see the different sizes and the different shapes of different neurons from different structures this huge motor neuron comes from the lowly locus of course this is much uh um uh blown up but you can compare this huge neuron in the Locust where a major thing is is is movement to this neuron in the monkey visual cortex doing major computations not that big um compared to Locus neuron but but also uh very important computationally we have zebra fish here rat thalamic neuron turtle neuron Tre shrew a tiny little monkey New World monkey here's a mouse neuron from the Globus paladis part of the um strial system uh here is a human retinal ganglia cell that we'll talk a lot a lot about in The Vision lectures um here is a pigeon tectum gandin cell and a v pigeon tectum paramal cell so you can see oh here's another monkey cell so you can see um that there are wides spreading um projections of these cells but it's just amazing to see how big an individual Locus cell can be and how small uh the monkey cells can be even though they're nervous systems are such different sizes okay so three common shapes of neurons that you should be familiar with this is one of the review questions um three major neuron types even though I should say that there are hundreds of different kind of categories of neurons these three shapes are the most common the most common of the three are called the multi-polar neuron multi-polar because it has many different dendrites coming off of the cell body um and um these kinds of neurons are common in cortex we'll be talking about paramal cells paramal cells in uh the hippocampus and in the cortex um that is a subdivision of the the multipolar neuron bipolar neurons are called bipolar for a reason they have a dendrite going out here and an axon coming out from the other side they're just kind of skinnier versions of the multipolar neuron and these are common in sensory systems for example in the retina there are bipolar cells a bipolar cell layer in the retina and finally um the third category is one that we've also talked about and mentioned before even though we haven't gone over the morphology it's called a mono monopolar neuron here a cell body uh kind of the one process comes off off the cell body and then it splits into the dendrites on one end and the axons on the other and these cells are the category of cells that transmit info from the body into the spinal cord now do you remember what uh we talked about uh there's a special uh compilation or grouping of cells uh near the spinal cord on the dorsal end of the spinal cord anybody remember what that's called what is a grouping of cells called Gang gangan so what is that grouping called on the dorsal part of the spine dorsal root gangling perfect and so these are the types of cells that are in that dorsal root gangling those gangling cells so cell bodies sit in that sack that I pointed to the kind of outcropping dorsal root Gangland and then their cell bodies are going out the dendrites are going out to um process information for for example in the sensory system the dendrites are here in my fingertips and then that dend dendritic information is bringing that sensory information in and then it it goes back out to the axons and this goes into the spinal cord and up through the samata sensory processing area Okay so three common types of neuron shape multipolar bipolar and monopolar okay so paramal cells a category of the multipolar neuron NE on are very common in the neocortex okay and so here what what I'm showing is simply a thin section through the cortex and uh what what it's stained with is a it's called a basophilic stain that only stains the cell body so we can see approximately the uh cell body uh size and shape but none of the processes the dendrites the stain is not um high enough resolution or it's not small enough to get into the dendrites and the axons so we're basically looking at um cell body stains and then each one of these individual cell bodies you if you would stain it with nissle stain sorry with a GGI stain you would see that it has these huge axons that go up this way this is layer one this is the outside of the brain the outside of the brain the outer covering uh corresponds to what's called uh the first layer of Cortex and as you go down towards the white matter um that is the axons you have um um typically six different layers I should say that layer one is cellfree um these are where all the axons are running so that means that the covering of the brain is made up of axons that are running across the surface layer two small cells uh uh very small called granual cells they're just small and round layer three cells tend to be a little bit bigger than Layer Two cells um layer four cells can differ um these are also a form of Gran granular cells and the deeper cells tend to be bigger there's a layer five and a layer six but these uh six layers are typically stained with what's called a nissle stain that's specific for cell bodies and you'll be looking at some nissle stains and possibly some Gogi stains I think in the microscopy uh lab in a few weeks now um what this is is a much larger section through one part of the monkey brain and here is what um I I show you this because this is one of the one of the most uh easy to see differentiations between two cortical areas um the art of uh uh differentiating between one cortical area and another just based on a nissle stain is called cyto architectonics which is the study of cell body CYO architecture with the nissle stain in the cortex okay so here is one region of Cortex and you can see there's a layer one here no cells layer two layer three layer four is very very thick here it has 4 a 4 B for C layer five has fewer cells and layer six is very thick and you can see that right here um this very thick layer four with these four subdivisions disappears this is is the differentiation and this is the boundary between area V1 primary visual cortex why why does it have such uh strong thick and differentiated layer four because this is where all the thalamic input from um thalamic visual input uh um inputs to the cortex and so this is a huge input area this is a transition between primary visual cortex and V2 or secondary visual cortex know uh um or much less um thalamic input into V2 and so it loses this very uh uh thick and differentiated layer 4 so this is just to give you an example of how you differentiate between these different areas of Cortex using a very common stain used since the 1800s the nissle stain we still use it today in the lab um let me just give you a a a quick overview of what people see that that's different in these cortical areas motor cortex primary motor cortex those brain areas that are going down and moving your toe going all the way down you'd think they'd have pretty kind of strong cells or big cells that go all the way down in fact they do can you see I know that it's it's hard from from the audience uh back there but can you see these bigger darker spots right here in layer five those are probably the largest neurons in the human cortex these are primary motor neurons in primary motor cortex uh that those are the ones that going out and controlling motor functions throughout the body okay you can see how different this is and the lack of these big old cells in association cortex higher levels of Cortex and finally this differentiates from primary visual cortex you can see this thick layer four this uh uh highly differentiated layer four right here okay so um I say this for a reason it goes back to the um history of studying which brain areas are important for what we talked about phenology that said well I'm not interested so much in the brain I'm just going to look at the bumps in the head that didn't turn out to be so uh so useful but um from the uh late 1800s early 1900s again during the same time that kahal was making his his um historic observation s many other neur animists were using stains exactly like this we using this stain the nissle stain to try and look and differentiate different parts of the cortex just based on how the cells were aligned and this gives you a a feeling for um all the different uh subdivisions that different people uh um came up with Smith in 1907 had uh subdivisions like this he actually didn't even use the nissle stain um I li he he uh took thin sections and simply look at them in the light and looked at how dense the light came through and he said okay well I have uh clear differentiation in these areas broadman did use the nissle stain he he looked at human brains and let me just tell you if you cut the human brain you saw how big it was if you cut it in 50 Micron sections that's a typical Fitness that you cut the brain in imagine how many sections you have to look at to characterize the entire human brain these guys were crazy they sat in their lab and they just looked at human brains and not only human brains monkey brains sheep brains rat brains um uh flying fox brains and tried to glean uh the the uh um kind of principles of cytoarchitectonic organization across these different brain areas and glean the function of uh or differentiation of brain areas and perhaps the function through side architectonics this is another beautiful one Von aono it's a a black and white drawing but the book that he published in 19219 was color it was actually beautiful and his descriptions were absolutely precise and easy to follow I know because I read them as I was trying to discover uh and characterize one part of the brain that hadn't been studied so much and comparing broadman and Von aono uh bradman's descriptions were very very vague uh hard to follow Von econos were very very precise but today it's broadman areas that are um used in fmri studies in lots of different studies to characterize the cortex and I've always been puzzled why broadman um ended up um with the higher um uh with with uh uh all the all the uh Fame and Fortune uh and Von aono did not and my conclusion is that he had better are he had uh easy to understand they were just broadman areas 1 2 3 4 5 6 7 9 10 easy to understand these were much more complicated even though the descriptions were were better and so it's broadman that we use even though I have to say that if you go back and read his primary work uh it's not nearly as detailed and beautiful as uh Von eono okay so now let's go into uh Gia cells second major uh component so gleo cells outnumber neurons 10 to one okay they outnumber neurons 10 to one but uh there are many many many different uh uh uh larger category of different neurons shapes sizes there are hundreds of different neuron types uh and only uh a a very small number for Gia types what do glea do first Gia means glue so so early neur anatomists thought that glea actually structurally held the brain together into all those folds that turns out not to be the case um they do a um a wide range of functions and I was mentioning they do even more than we appreciated and that is a very very hot area of research right now in Neuroscience one they communicate with each other and with neurons and we thought that they did kind of just support functions they're just there to support the neurons but in fact more and more research has been suggesting that they're doing some computations similar to neurons as well and they are not just support but they're critical support for the computations that these specialized neurons are doing um they provide raw materials and chemical signals um that we'll talk about in a second they provide protection for neurons um for example there are gleo cells that form kind of a barrier around a particular synapse not to let other in uh inputs in and perhaps to to um sheath that particular synapse so that the neurotransmitters aren't flowing out and flooring in they can form kind of a physical um boundary and they do damage control if there's damage in the brain for whatever reason they can phagocytose uh the damage coming up and as part of that damage control they do a lot of the debris removal if a cell dies or again if there's damage okay four major types of Gia cells you need to know all these major major types first asites asites nourish and support and scavenge at the synapsis we're going to be looking at individual examples of these microa as the name suggests they're much smaller they multiply at injury sites and seal the area and they also help to remove the the the debris um oligo dendrites and Schwan cells both of these make myin sorry this should be highlighted in blue as well oligo danger sites make myelin in the central nervous system and Schwan cells are are uh uh the the category of cells that make myelin in the pns or the peripheral nervous system okay so two of these types of cells are specialized for making myin we'll talk about what that means and two of them are uh support and injury support for cells in various ways why should we be interested in Gia well the main reason um right now and that that we know the most about is disease States and disease States involving uh um problems with myin multiple sclerosis is a degeneration of the myin coating so we're going to talk a little bit about exactly what myin does but if you uh um if your myin starts degenerating you have severe problems in in this case in motor movement so multiple sclerosis you get myin degeneration in the motor system um glea are also implicated in many disease States so GAA form many of the tumors that arise in the in the brain Goma is a proliferation of Gia that could happen um if the uh um Gia are are um uh reproducing at the uh injury site or there is uh simply a tumor a a malfunction of this plation function uh of the Gia and that turns into a a brain tumor that can be very dangerous and asites also uh their their role is to nourish and support and scavenge but they also swell in response to in injury that can cause the um brain edema that happens with brain injury brain edema is terrible because what happens with the brain it's encased in the skull you um you swell up too much and you start doing physical damage and shearing damage to the brain itself okay so um uh these are just three examples of um uh uh disease related aspects associated with Gia cells okay asites in microa um asites here uh do some really very important roles they detect neural activity and regulate uh adjacent capillaries why is that so important it's so important because um neurons uh really need blood supply to be able to react to what they need to do and um that is why uh if you have even a a temporary um uh slowing of blood to the brain you can get woozy you can faint is because your neurons need that blood and that oxygenated blood um very very carefully and what asites are doing is they are monitoring how much the cell is active and if they starts to really fire a lot and use a lot of energy what the asides can do is say hey capillaries expand let's get some more blood into this area a critical uh uh a critical function microa uh important for all kinds of injury from you know severe traumatic brain injury to whatever happens when you when you bump your head um uh we talked about you bump the back of your head and you see stars because you're stimulating the primary visual cortex you're also bruising your brain and this is also what we talked about um uh in terms of uh the athletes that that tend to put their heads In Harm's Way a lot uh with a lot of uh physical contact the the football players probably have enormous amount of microa that are proliferating in their brain to help uh um phagocytose the uh the damage and the bruising and the death of the cells that are happening uh with increased um uh um contact and increased concussion microa work to break down debris that forms um especially after damage in the brain okay and so finally I want to end with the idea of um uh myin and what it's doing so we talked about the oligodendrocytes and the Schwan cells whose role is to make myelin myelin is um a fatty substance it looks white when you simply look at the brain cut it in in different uh uh subsections and um what these oligo dentrites do is it produces myelin and it wraps around around uh the axon so this is the axon cut in cut in cross-section and what you can see here is layer upon layer upon layer of this myelin wrapping this fatty wrapping it's just like an insulating um uh substance uh It Coats uh long axons are typically coated with with uh myelin and short axons are bare why because the major role of myin is to help synaptic transition uh transmission it is actually um helping the uh uh electrical activity go faster down the axon so that when you say I want to move my toe you can do it very quickly or when a soccer player or a soccer um goalie has to actually react uh to those penalty kicks they can dive in a very very fast action that is all because of the fast conduction that you're able to do down your aons down your motor cortex to um to all of your muscles and that is why if you have damage to uh either the oligodendrocytes or the Schwan cells making uh milin that you start to have Motor problems and slowing and weakness in the muscles that are so um um uh characteristic of multiple sclerosis um okay so what typically happens is that there are multiple uh um uh wrappings uh around a long axon so a long axon will be uh all the way down here you'll have a wrapping of milin here and then there'll be a little Gap a wrapping here little Gap little wrapping here and the gaps here are two wrappings in a cross-section here's a gap so here we're seeing the axon the axon is bare and in between these two gaps are wrapping of myin this um uh bare Gap is uh important structure called the node of romv you need to know this the node of romv is again the the blank portion where you go down to the axon this is where the um action potential those electrical activities will jump to and then fire off again and they'll jump to the next node of ROM VI and that jumps the um um allows the uh action potential to go faster and faster down the axon we're going to cover this in in Greater detail but you do need to know and I wanted to introduce the concept of the node of romier uh um uh early uh here as we're talking about milin okay um and then lastly uh oh here is a picture at a higher magnification of these wrappings of individual kind of layers of this fatty myin substance you can see how precise it is and how it's just kind of wrapped with string over and over and over to provide a very thick um insulation for the axon here you see a mitochondria within the axon part of those uh uh major structures that you see in all cell uh cell types and finally while the long axons are typically myelinated not all axons are myin myelinated some are unmyelinated and but they tend to be wrapped around um uh and and held together with a sheath of myin this sheath of myelin isn't helping um um electrical conduction but it just helps them kind of uh group together so here is a bunch of unmyelinated axons so these have slower conductions this is uh these are axons that you need um you don't need as much speed and then they're all grouped together around uh um bundled in a sheath of myin so two different types of of neurons okay so that is all I have today um next Monday oh very very important I will say that the next three lectures are really going to be the core of this first um exam these are the concepts that you need to know so I would highly recommend that you all read the chapter on electrical and and chemical synaptic transmission before Monday's lecture you'll get the most out of it it is dense and we're kind of going to jump in to the hardcore Neuroscience uh next Monday so come prepared for that have a good weekend

Channel: New York University

Views: 37,094

Keywords: nyu, Wendy Suzuki, Brain and Behavior, New York University, NYU, Open Ed, Open Education, neurons, glia

Id: Kfsb6JHutJA

Length: 63min 24sec (3804 seconds)

Published: Fri Jan 04 2013