hey everybody welcome to chapter 14 the brain um you know it's a lot to talk about here please understand that in one chapter out of you know i don't know how many chapters 30 chapters in a standard amp textbook in one chapter of that we're going to talk about the brain uh you know and this is an entire area of biological science so there's only so much we're going to learn about the brain we're going to learn the major structures we're going to learn about the csf circulation we're going to learn about some some very basic things you know the major brain structures which you will be reinforced with in lab and some basic functions of each part and what i hope to be able to do is just in part to um a general sense of how your central nervous system especially the brain functions to coordinate your activities okay you're going to have questions and you know these are the types of things that you move on with in your education and learn about in future coursework or on your own so we're going to start here i've got a image in front of you that's just got basic superior view lateral view of the brain here superior here lateral here here's the cadaver lateral view just to point out you know if we look at this from the from the lateral view here we generally separate the brain into the brain stem region okay and the cerebellum here and the cerebrum up here now when people think about the brain you know it's the cerebrum generally that gets all the press but what i want to show you is how critically important the brain stem portion is especially and how integrated the cerebellum is into all these other functions so there's a lot of physical vocabulary on this diagram which you will be learning in lab that's so it's a question of how much to go into here in the lecture so what we're going to do is i'm going to just give you a little bit of overview of some very basic structures just so it gives us room for conversation so keep in mind the brain like the rest of your central nervous system and most of your body shows bilateral symmetry so there's a mirror image left and right side and what that does especially with the cerebrum here if we look at it from the superior view looking top down there is a right cerebral hemisphere and a left cerebral hemisphere and that is separated by a fissure so we talked about fissures versus sulci when we talked about the spinal cord so the spinal cord has an anterior median fissure but has a posterior median sulcus so the longitudinal fissure is an actual separation okay there's there's a gap there it's filled with tissue that i'll show you on the next panel but what you'll see here is all over the surface of the cerebral hemispheres are folds and ridges so what you have here is where the tissue comes out here we call that a gyrus let's see if they yeah they have it labeled as the pleural gyri so you see where the tissue folds out towards you and has a little ridge of tissue right here let me get my pen here this is a gyrus and then where it dives down in this is a salt a sulcus here so there are cerebral gyri and cerebral sulci those are the plural for those terms these uh gyri and sulci are exquisitely mapped so if you take a neuroscience course they could tell you pretty much what each square centimeter of every gyrus does as far as what types of stimuli and response they're responsible for we won't go into that here there are a couple of gyri and sulci that we pay attention to here let's see one of those here is the central sulcus and you know you it's not like you can really tell by looking at it where it is but it's an important landmark and we teach it to you in lab on the models we also have the lateral sulcus here and depending on the resource you have some of the textbooks like this one that this image comes from we'll call it the lateral cerebral sulcus some textbooks call it the lateral cerebral fissure so it's it's somewhere in between a sulcus and a fissure so we we pay attention to those because what it does is it distinguishes for us the lobes so we have for example a temporal lobe a frontal lobe a parietal lobe an occipital lobe so if we take a look at the map here of the cerebrum what we have is if i look over here oh i got to get a pen out hold on if we look over here there's your central sulcus here and what that does is it separates the frontal lobe from the parietal lobe all right and then if we look over here the lateral sulcus so here we have the frontal lobe here's the parietal lobe underneath the lateral sulcus this is the temporal lobe and then way back here we have the occipital lobe that's the ones labeled way over here so we're going to by the time we're done with this chapter i have taken a look at each of these lobes and try to understand what their jobs are what the what kind of activities they're responsible for other thing we pay attention to here in this chapter as far as these gyri and sulci you have the central sulcus here and i've got it here there is a gyrus anterior to that and a gyrus posterior to that those particular gyri those particular cerebral ridges are pretty important for some of the things that we talk about so i'm going to lay in here here's our central sulcus here and they label that there and then what we have here is we have a gyrus behind that and we have a gyrus in front of that our gyrus behind that is the postcentral gyrus our gyrus in front is the pre-central gyrus those are those are rather important i want you to pay attention to those when we learn them in lab and then towards the actually towards the end of this chapter we're going to talk about their function and we've actually already encountered them but i i ignored them because i wanted to wait until here so when we in chapter 13 discussed ascending and descending spinal pathways the a sending sensory pathways end up in the post central gyrus all of those third order neurons from the thalamus projecting to the cerebral cortex all come here and then the descending motor pathways all originate from here so the upper motor neurons all originate from here so if we look at the postcentral gyrus here we call this the primary somatic sensory cortex so it's the i'll break this down for you cortex means cerebral cortex that's where we're at primary somatic sensory cortex so somatic sensation is your sense of touch all of those ascending pathways we're all carrying some form shape or fashion is you know environmental stimuli that we call touch and all of that is coming here so primary that's the term we use in the central nervous system for the brain anyways where stuff first ends up all right or first originates from so there are other areas of the brain that deal with some meta somatic sensory information but it all arrives here at the post center gyrus the pre-central gyrus over here since this is where all upper motor commands come from we call this the primary motor cortex all right because that's where all of your motor commands the actual commands come from this piece of cerebral cortex now the planning for these commands comes from the frontal lobe we'll talk about that but the actual upper motor neurons originate their somas their cell bodies are in this cortex all right the other thing i wanted to point out here uh way up the top terminology we've been dealing with you know duplicating terminology so for example we learned that anterior is the same as ventral and that posterior is the same as dorsal well here anterior equals ventral equals rostral posterior equals dorsal equals caudal for whatever historical reasons neuroscience settled in on these terms for directionality in the brain so rostral rostrum in latin means nose or snout so rostrol means towards the nose caudal means tail towards the tail so that's posterior so these are the terms that you will see applied to directionality in the brain so i didn't want you to be confused by that if you're reading these things if we come over here look look what was hiding over here i found another diagram if we look here we see a sagittal section view of the brain where we have basically divided the brain into a left and right side and we're seeing right side or the right hemisphere of the brain this allows me to show you much more in detail here this idea of the brain stem so here's what we call the brain stem and it's going to include these structures here all right i guess i could have made that a little bit clearer because that black doesn't show up very well there we go make it a thicker line there's your brain stem okay and then over here this is your cerebellum and then up here this is your oops this is your cerebrum so the cerebrum really just sits like a like a big mushroom cap on top of that brain stem stalk with a cerebellum sitting behind and on down here they show you the sectional plane you're looking at so that's carved right down the middle of that longitudinal so if we look in here this is part and parcel of what you're going to be doing in lab here's a cadaver section you can see how these gyri and sulci of the cerebrum you know fold and dive in and come out and make ridges and valleys there is a sulcus here that separates the parietal lobe from the occipital lobe you know there's a big fissure here that separates the cerebellum from the cerebrum you know you can see the different parts of the brain stem you can see some parts are darker and some parts are lighter that's gray matter and white matter so it's it's neat i don't want to go too far into you know corpus callosum and the thalamus and this and that um we'll do this one step at a time and much of this you'll learn explicitly in lab but this is what it looks like in a half section and oftentimes we'll be looking at it like this but we're going to go through the anatomy of the brain from the bottom up so we're going to start in the brain stem with the medulla oblongata move into the pons then the midbrain then the diencephalon and then we'll take a look quickly at the cerebellum and then we'll end up in the cerebrum so we're going to move our way upwards here and we'll go over each part as we go what we'll do first though is we're going to take a look at the meningeal system the meninges the pia arachnoid and dura mater and we're going to take a good look at cerebrospinal fluid circulation and production so let's uh let's see what we got there all right so here's a couple of diagrams i'm going to focus in here on the one on the left first let me zoom in a little bit all right what do we got here uh look down here i'm taking kind of a funky uh coronal slice here a thick coronal slice and pulled it out like a drawer and if you look here we are okay here's the skull bones uh so here's um the right and left parietal bones with the sagittal suture holding them together and as we go deep to those parietal bones what we find first here is the dura mater so i'm going to highlight that here there you go there's the dura mater what we see here is that around the brain the dura mater is a dual layered membrane it has two layers so i'm gonna highlight i guess these two layers so the first layer here slides right along underneath the bone and in fact it is intimate we say with the periosteum of the bone so that would make that the periosteal layer here of the dura so it comes down like this so there's that periosteal layer so it's a dense fibers connective tissue it's very thick very durable tough that's where it gets the latin name dura mater and it is uh intimately associated you know with the periosum it is not the periosteum but is very tightly linked to it physically and has fibers that link together with it and interestingly enough one of the things that stabilizes the brain inside the cranial cavity is if we take a look at the collagen fibers of the periosteal dura at the suture lines those fibers kind of crawl into those cracks of the sutures and integrate themselves with the ligaments that hold the two skull bones together at that suture and so that uh you know at the coronal suture satin suture the lamboid suture the squamous suture all of those skull plate sutures the periosteal dura is sewn right in to that suture line that's pretty cool okay so we'll take a step out here for a moment what we'll do now is we'll focus on the meningeal layer so we have another layer here so this layer is underneath the periosteal layer and for much of the surroundings of the brain travels directly with the periosteal layer so that they are pretty much one and the same and it's only at certain points like here you can see when we took this coronal slice where that's coming from there's the longitudinal fissure of the two between the two cerebral hemispheres so this is the right cerebral hemisphere here's the left cerebral hemisphere this is the longitudinal fissure and we look here at that fissure and any other fissure or major sulcus we find the meningeal layer diverges from the periosteal layer and goes down into the fissure and when that happens here it creates a space and that space is going to be what we call a sinus right so in this case because this is in the longitudinal fissure which is also sometimes called the sagittal fissure we call this the superior sagittal sinus because it's out on top here and it creates a space and that's actually going to be a space to collect venous blood and return venous blood from the cranial cavity to general circulation through the jugular veins i'll show you that here in a bit so when we take a look at the dura mater we have this periosteum energy layer and where those layers diverge we create sinuses now that's why i brought in some of these other images so i'm going to come down here and this is a different you know wider look of this same phenomenon so i'm going to outline here so here's that periosteal dura okay i'm gonna keep my color coding the same from the previous diagram so there's that periosteal dura it just runs right underneath the skull plate here's that meningeal dura most of the you know most of the surface area it is one in the same with the periosteal dura they basically travel as one membrane but where we approach this fissure they diverge and the meningeal layer goes down into the fissure where it goes down that creates our superior sagittal sinus that space right there okay great now when it gets the bottom of the fissure it has to make a hairpin turn i mean it ends this this fissure doesn't go forever right so when it comes down here it has to turn and come back up the other side and where it does that it creates another sinus and this is the inferior sagittal sinus because it's down deep and this is up top superior inferior so this creates two spaces for venous blood accumulation so as blood goes through capillary beds through the center of the cerebral hemispheres the venous return is actually through these sinuses right so we come back here uh so that's what they're showing us here they uh just didn't you know take it all the way down to show the inferior sinus now what about the other layers so we have here the arachnoid motor so they're showing this um thin translucent membrane barrier here there's the arachnoid motor i guess i could highlight that i got plenty of colors to work with here's the arachnoid mater here okay so that lies just underneath the meningeal layer of the dura so there is a subdural space they pointed out here between the meningeal dura and the arachnoid mater it is a potential space only okay i'll write this in and get a right size pen here the subdural space here this is what we call a potential space and normal physiology there's no space there the two layers are directly adhered to each other so if you have like a a subdural hematoma that means bleeding has taken place into that subdural space and blood has filled in between the arachnoid mater and the meningeal dura but in normal physiology there's nothing there but underneath the arachnoid mater we have the subarachnoid space now before we get there we have to pay attention to the pia mater so the pia mater we knew from the spinal cord is the innermost layer of the meninges adhere directly to the surface of the spinal cord and here is adhered directly to the surface of the cerebral cortex if you take a look here there's there's actually relatively speaking a substantial space uh between the arachnoid mater and pia mater that is the subarachnoid space okay and this subarachnoid space that's where cerebral spinal fluid is circulating okay and we're going to take a look at that in detail here so here's uh you know kind of a basic look we'll worry here about this arachnoid granulation in a little bit um but if i come over here this gives uh you know i i have a pretty good look at these same concepts so there's your skull plate you know parietal bone for example here's your dura mater with the two layers the periosteal dura and the meningeal dirt and they show the meningeal dura diving down into the longitudinal fissure they show the arachnoid mater with that subdural space that potential space they show the pia mater over the surface of the bare cortex and they show the subarachnoid space underneath there so this kind of gives a good look at that that layering of all of these structures so that's a an introduction there to these meningeal layers and what i want to do now is briefly talk to you about where these meninges dive into these fissures creates tissue structures that i want to show you so let's take a look so the lecture outline if you look in front of you i'm assuming you have it in front of you uh top of the first page under meninges you know we have dura mater or the periosteum and gilder then i have dural folds all right dural folds that's these things here all right this is what i want to pay attention to here now when we talk about these dural folds you just take a look at the previous diagram it's not just the dura mater the meningeal dura but it's also the arachnoid and pia but that's the dura is what gets the name uh gets the the naming rights here i suppose but there are three major dural folds where the meningeal dura dives away from the periosteal dura and the one that we were using just previously was between the hemispheres of the cerebrum okay uh so this is a sagittal view sagittal cut here here's with the left cerebral hemisphere in place and then they've taken the brain out just to show where these draw folds are so remember all you've got to do is just look at look at your diagrams i can't go back and forth easily in this format so just look at your diagram diagrams what we were just talking about and you had the meningeal dura passed down into the longitudinal fissure and that created at the top there that superior sagittal sinus and then the folds go down to the bottom of the fissure make a hairpin loop and come back and that made a sinus at the bottom of the fissure there's the inferior sagittal sinus and if you were to remove all the brain tissue what you would see is a sheet of meningeal dura along with the arachnoid and pia mater that went with it but this is that sheet of meningeal dura that passes down into the fissure makes a hairpin loop and comes back out creates a sinus on top a sinus on the bottom these sheets of tissue have names these are the dural folds and this major one here the biggest is between the two hemispheres of the cerebrum and it's called the falc's cerebri and falcs in latin means sickle so it's a sickle-shaped dural fold between the cerebral hemispheres the falx cerebri and that creates two sinuses superior sagittal sinus inferior sagittal sinus and again these are where venous blood accumulates after passing through the cerebral capillary beds and then it returns the circulation through these sinuses so it basically percolates upwards here for the superior sinus and then starts here right behind your eyebrows and it flows this way and then the inferior sinus it percolates down it flows this way okay so that's the falc's cerebri it's between the two cerebral hemispheres now there is a another one here if we come over here what you'll see me make my pen nib larger what you'll see is that same phenomenon of the meningeal dura separating from the periosteal dura and it'll come in here between the interface of the cerebrum and cerebellum and i'll come back out like that and that creates a sinus right here and a tiny little sinus there just like it like before if i come over here that's the membrane called the tentorium cerebelli the tantorum cerebelli comes across like this and it actually creates a little circumferential sinus around it tantorum a tent over the cerebellum if you think about its position here uh that forms a membrane sheet over the top of the cerebellum that's where it gets tentorum cerebelli so the major sinus here is the transverse sinus right and what you'll see is the transverse sinus is where the superior sagittal sinus drains into and the inferior saddle or sinus can drain into it also these are things that we will look at in lab actually you'll learn the names of the major sinuses the third dural fold here the cerebellum itself actually has hemispheres all right let me show you this oh look at that look what was hiding over here here's a look at the cerebellum now if i i realize it's going to be kind of grainy but if i zoom in over here you know that that tentorium cerebelli is going to be separating the cerebellum from the cerebrum as a dural fold but there's also a hemispheric separation here with the left and right hemisphere so there's actually a fissure between the left and right lobes or hemispheres of the cerebellum it's small but it's there and there is actually a dural fold that goes in like that and creates a sinus right there so if we look at that here's the falcs cerebelli right so it's not a very deep fold it only has one sinus but that is the falc's cerebelli those are the three dural folds so falx cerebri tantorum cerebellar phalx cerebelli and they create these sinuses and that's where venous blood drains out of the cranial cavity i'll show you that um in lab with our models so there's a discussion on those dural folds and now we're going to return before we're done to the superior sagittal sinus because when we talk about cerebrospinal fluid when we talk about its formation circulation and reabsorption the reabsorption of cerebral salmon cerebrospinal fluid takes place in the superior sagittal sinus so i'll show you that now the last thing i wanted to illustrate for you is you can see it on the other diagrams too but here it is and i forgot to talk about on a previous one so we'll do it here there's uh there's a reason why the arachnoid mater is called the arachnoid monitor so arachnoid means spider-like because between the arachnoid mater and the pia mater here let me zoom in a little bit so we've got uh the arachnoid mater here and we've got the pia mater here and between the two you have these filaments i should do them in purple you have these filaments that come down and provide this support structure to keep this open and provide a space for the cerebral spinal fluid to circulate and that looks like spider web and so that's where it gets the term arachnoid mater so there you go all right so let's take a look at cerebrospinal fluid all right so here's a set of diagrams where i want to try to get you to understand that your brain and spinal cord are hollow so i've mentioned this before with the spinal cord but here we are in the brain your brain is hollow so to speak there are chambers in the middle filled with fluid and these chambers are called the ventricles so take a look here they're showing you they're taking a kind of a transverse section through the brain right above the eyebrow and when you do that this is what you find and right in the center here see these uh these these holes i mean these are the ventricles of the brain and this is where cerebral spinal fluid is okay up above here they're showing you basically the relative position of these ventricles and their shapes if you're looking straight on here take a look at the right side here if you're looking straight on what you see is you have two large ventricles that look like rams horns sitting on the side and then they are connected centrally medially they drain into a common space here right so this right here is another ventricle these are the lateral ventricles here is the third ventricle there is a duct here that goes to another ventricle the fourth ventricle and that enters the spinal cord as the central canal of the spinal cord and here it is from the side you can see here's your lateral ventricle and it's hard to see from that anterior view but it's that ram's horn goes away from you down and back towards you so it goes like this back and towards you and has a little tail off here so there are other complex structures and the lateral ventricles are quite large where you have the drains here from each lateral ventricle to the third ventricle you can see them here those are called the interventricular foramen or foramina here's your third ventricle there and then you have a duct the cerebral aqueduct that drains down to another space the fourth ventricle here and what you'll see is the fourth ventricle is right in between the hemispheres of the cerebellum in the brain stem there's an intersection where the cerebellum and the brain stem meet and that intersection is the fourth ventricle and then that fourth ventricle drains into the central canal of the spinal cord so over here i've got kind of a a nicer color-coded view of the same thing uh it's just you know gives a good overview of the type stuff we're looking at so in blue here we have the lateral ventricle now there are four ventricles one two three four and they go from superior inferior it just happens to be the ventricles one and two are the lateral ventricles and then ventricle 3 and ventricle 4 in yellow so lateral and blue third ventricle green fourth ventricle yellow and you can see the cerebral aqueduct as it goes down and then continues into the central canal the spinal cord so this is your cerebrospinal fluid circulation system so we need to do is we need to take a look at how we produce cerebral spinal fluid how it circulates and what it's for so let's keep moving on all right let's take a look at this diagram this is one of those fun ones where you know follow the bouncing ball one two three four five six seven eight well i'll carry you through it but when you're looking at it later these are kind of nice to keep you on track right what do we got here we have half a brain so we have starting at the spinal cord down here there's the medulla there's the pons there's the midbrain we'll talk about these here in a bit there's the cerebellum cerebrum they've kind of artificially separated these structures to show you the spaces in between them not really this open but for the purposes of this diagram they kind of pull them apart all right starting here number one now in the middle of the brain here right where the cerebrum sits on top of the brain stem uh behind the screen here right right where my pointer is right where the number one is if you go into the screen back in there is a lateral ventricle so on this person here this would be the right lateral ventricle now if you were to come away from the screen towards you into space you would enter the left lateral ventricle it's kind of hard to think sometimes three-dimensionally but if you have printouts of these images keep the previous diagrams in front of you so you can kind of see that three-dimensionality so we have that lateral ventricle that's back in the screen there and you see that red stuff there and you see some red stuff here and you see some red stuff here all right this red stuff here is choroid so i'm plexus to come over here choroid plexus this is ependymal tissue so go back and look at that chapter 12 material where we went over nervous tissues and we talked about the neuroglia and these are the support cells of the nervous system and one of those types of glial cells are ependymal cells so this is ependymal tissue and these choroid plexus structures these make csf cerebral spinal fluid so the choroid plexus is where you're producing cerebrospinal fluid how do they do this they extract plasma and certain ions from capillary beds and pull it into the ventricles so the choroid plexus material that the actual tissue those structures looks bright red because it's full capillary beds it's highly vascularized and they're from those capillaries the ependymal cells are pulling selected components of plasma see these arrows here so they're showing you from the capillary beds are pulling that out and creating cerebral spinal fluid each ventricle has choroid plexus in it so there is chloride plexus in the lateral ventricle there's chlorate plexus in the third ventricle there's even choroid plexus in the fourth ventricle now what they're showing you here is that the choroid plexus of the lateral ventricle continues down through this connecting duct here the interventricular foramen and it is the same physical structure as the cory plexus and the third ventricle so up here let me write something here this is lateral ventricle this is third ventricle this is fourth ventricle and at the very least the choroid plexus of the lateral two ventricles and the third ventricle are all the action actually all the same structure and it continues through that form and that opening there so we're producing csf in the ventricles and then what's happening is we're circulating it so let me zoom back out here we'll we'll read our storyline here one csf is secreted by cory plexus and each lateral ventricle number one csf flows through the interventricular foramina into the third ventricle where you have more choroid plexus in the third ventricle adds more csf there csf production flow production flow so now we're going to come down csf flows down the cerebral aqueduct to the fourth ventricle here's the cerebral aqueduct now we're in the fourth ventricle number five here see cory plexus and the fourth ventricle adds more csf sorry we've got all this csf where it's gonna go now it's going to escape the ventricular system now some of it will go straight down the central canal the spinal cord so csf is and fills the central canal spinal cord most of it though exits the ventricular system through apertures here let me highlight this there's a median aperture here and there's two lateral apertures one on each side so there's three apertures so we come over here number six csf flows out two lateral apertures and one median aperture where does it go it goes into the subarachnoid space so it leaves the middle of the brain the hollow lateral you know third and fourth ventricle system it leaves that and it enters the subarachnoid space and now it's going to flow around the outside of the brain and it's going to end up coming way up to the top here eventually so it's flowing around the outside of the brain it flows down around the outside of the spinal cord all the way down to the cauda equina and the lumbar cistern it's going all the way down coming all the way back up it's just flowing and bathing the entire central nervous system inside and out so what's the cerebrospinal fluid for well it's basically a secondary way outside of the capillary beds you know vascularization of the brain it's a secondary way to provide nutrient delivery and waste removal from the central nervous system tissues there's a lot of current research going into cerebral spinal fluid and its circulation patterns one very fascinating new finding is that during sleep especially during the sleep deep sleep stage where you're not dreaming it's very apparent now that cerebral spinal fluid circulation greatly increases during that time so it looks like maybe this plays a real role in um rejuvenation of um you know the the the i guess what's the term rejuvenative value of sleep uh there's uh conjecture that it has a major role in removing um toxic metabolites that build up during waking hours so it's a lot of research going into that right now but here's your your map of csf circulation production circulation and now reabsorption occurs up here i said we would return to the superior sagittal sinus because that is where we are reabsorbing cerebrospinal fluid go back a couple of slides earlier on your notes and you'll see in that very first slide where we looked at the periosteal and meningeal dura there's the arachnoid granulations and here they're calling an arachnoid villus but there's these projections of the arachnoid mater into the superior sagittal sinus and that's where cerebral spinal fluid escapes the subarachnoid space and returns into the venous blood so it's extracted from blood in the ventricles it returns to blood in the superior sagittal sinus and put some numbers on this you make about 500 milliliters per day production but there's about 150 milliliter capacity so you are recycling you know producing and reabsorbing about two two and a half times every day so there's uh there's a map of the ventricular system and cerebral spinal fluid