Neuro: 2:00 - 3:00 Scribe: Ashley Brewington
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Neuro: 2:00 - 3:00 Scribe: Ashley Brewington Wednesday, February 10, 2010 Dr. Nicholas Cerebellum Page 1 of 9 I. Motor System: Cerebellum [S1] a. If you remember me, I’m Dr. Nicholas from the department of neurology and we are going to switch gears again and go back to anatomy. b. You have heard about all parts of the brain except this one. So we will spend a little time on the cerebellum. II. Overview of Motor Systems [S2] a. Now the cerebellum is part of the motor system and as you should recall from previous lectures the main motor pathway that allows us all to move is the corticospinal pathway. b. The corticospinal pathway starts in your motor cortex, but there are two other parts of the brain that refine your movement. i. One is the basal ganglia which you have had a lecture on. ii. The other is the cerebellum. c. The cerebellum is known for controlling fine motor movements and also it has something to do with balance and motor programming. d. So, that is the cerebellums major function. It helps the motor cortex do its thing. III. Gross Anatomy [S3] a. During this lecture, as far as gross anatomy is concerned there are some things that you need to know. b. These structures such as the flocculus, anterior lobe, posterior lobe. IV. Know This Stuff [S4] a. You can read them all here, we are going to go through each one of them in picture form. V. Cerebellum: Gross Anatomy (ventral view) [S5] a. This a picture of the cerebellum, it has been plucked from the brainstem and you are looking at the under belly of it. b. Just to orient you, this is in the caudal direction, towards the tail, and this is in the rostral direction, towards the nose so to speak. c. You can see this smooth structures here, that have been cut to allow you to remove the cerebellum and those are the big columns that connect the cerebellum to the brainstem or the cerebellar peduncles. d. Even though it looks like its one big lump on either side, it has been divided into three major areas. The largest one that sticks out like this, is the middle cerebellar peduncle. The one that goes rostral is the superior cerebellar peduncle. The one that goes caudal is the inferior cerebellar peduncle. e. But when you are looking here, one of the things that you may notice is that the cerebellum is all pretty monotonous. It has ridges in it known as the folia, where the cells are. It is like the cerebral cortex where the cells are on the outside on the surface. f. One of the things that the anatomist notice on the back of the cerebellum are these two lumps that are coming off the cerebellar hemispheres which reminded them of inflamed tonsils in the back of the throats so they called them the tonsils. The tonsils are part of the cerebellar hemispheres and are very important in that when there is pressure in the head and you herniate the brain and you push the brain through the foramen magnum this is what goes first. Once that happens it is bad news. There are some people that are born with their tonsils a little bit sticking out of the foramen magnum and is called Chiari Malformation. It is not always a bad thing to have the tonsils sticking out a little bit, but the anatomists thought this is what that looked like. g. They also thought this midline structure kind of resembled a worm. I don’t know if I agree with that. The word for worm is vermis, so as a result they called it the vermin vermis and this is where some of the names of these structures come from. h. The last bit of the vermis is called the nodulus. The nodulus is attached to these two little flaps on either side called the floculi. Together they make a lobe called the floculonodular lobe. VI. Cerebellum: Gross Anatomy [S6] a. So in the midline saggital section again to orient you this is frontal/rostral and this is caudal towards the tail and here is the brainstem cut down the midline and here is the cerebellum. b. And since the midline structure is the vermis, when you cut through the vermis, what you see is this tree-like structure it looks like a bush. Even though the vermis looks like a worm from the previous picture, if you cut it down the midline it looks like a little bush. All of these little branches of the bush have names, but you don’t need to know them all thank goodness. c. You do need to know the last one, which is the nodule. The posterior lateral fissure separates the nodule out from the rest of the vermis. VII. Cerebellum: Gross Anatomy [S7] a. Again what you are seeing here, all of this, is the vermis. b. The cerebellum itself is divided up into lobes. You have an anterior lobe here in blue and posterior lobe in green which includes the tonsil. c. The nodule is in red here. VIII. Functions of Subdivisions of Cerebellum [S8] Neuro: 2:00 - 3:00 Scribe: Ashley Brewington Wednesday, February 10, 2010 Dr. Nicholas Cerebellum Page 2 of 9 a. Functionally, to make since of the cerebellum does and its anatomy is we divide the cerebellum into three parts. b. The three parts are shown in the different colors here. c. They kind of go in a temporal form as in how they were developed, so that you have: i. Archicerebllum: ancient; primordial cerebellum; F-N lobe; inner ear and eyes; fastigal nucleus ii. Paleocerebellum: old; old cerebellum; vermis and paravermis; trunk; interposed nuclei iii. Neocerebellum: new; new cerebellum; cerebellar hemispheres including the tonsils; limbs; dentate nucleus d. In this picture, the bluish-purplish color is the archicerebellum, and so primarily this is the floculonodular lobe. e. In the pink, is the paleocerebellum and makes up the rest of the vermis and the paravermis which is the area just next to the vermis, para means next to. f. The neocerebellum is in green here so these are the cerebellar hemispheres which includes the tonsils. IX. Picture [S9] a. So, realize also just like in the cerebral cortex you have certain parts of the cortex that correspond to certain parts of the body. You can actually draw a human-like picture of the cortex which is called the homunculus, meaning little man. b. On the cerebellum, you can draw three homunculi and the homunculi gives you a clue about what the different parts of the cerebellum are doing. c. You can see that the vermis region and paravermis region what parts of the body are right there in the midline? Well it is primarily the trunk. d. Out in the cerebellar hemispheres is where the limbs are. e. So, what is not in the picture is what the flocular-nodular lobe does, and that is sort of like inner ear and eyes. f. Again, the cerebellum is used for movement to coordinate movements, so these are sort of to try to get in your mind how to organize the cerebellum. Hopefully, this will be helpful for you later on. X. Nuclei [S10] a. Now the other thing that you need to know and we are going to tell you about the cytoarchitecture of the cerebellum in a few minutes, but all information coming from the cerebellum has to synapse in nuclei first. b. The nuclei are found in the white matter, deep inside the cerebellum and as a result these nuclei are referred to as the deep cerebellar nuclei. c. There are four nuclei on either side. d. The kind of rule of thumb is, and it makes anatomical sense that it would be this way, the most outer parts of the cerebellum synapse in the most outer deep cerebellar nuclei. e. The neocerebellum out here, will synape on the outer most nucleus which is known as the dentate nucleus. f. The paravermis and vermis, which makes up the paleocerebellum, synapse in these two purple nuclei called the interposed nuclei. i. These are two nuclei, one is called the eboliform nucleus and the other is called the globose nucleus. g. The inner most here in yellow is the relay nucleus for the archcerebellum and it is called the fastigal nucleus. h. Outer goes to outer, middle goes to middle, and inner goes to inner and that makes anatomical sense. i. As far as your little chart here (on board), that archcerebellum is going to be fastigal; paleocerebellum is going to be interposed (globose and eboliform), and the neocerebellum will be the dentate nucleus. (see chart under slide 8) XI. Nuclei [S11] a. If you are talented enough to do this, dissection, you can actually carve those nuclei out so all of the white matter has been carved out to show you these nuclei here. b. Again, you have the dentate nucleus, the eboliform nucleus, the globose nucleus, and fastigal nucleus. XII. D, E, G, F [S12] a. Another way of looking at it is with a myelin section. b. This is a section through, you can the rostral medulla, above that is the cerebellum and everything here that is in black is myelin (white matter; everything that is black is white matter), all of this white matter is stained and within this white matter are the deep cerebellar nuclei. c. The outer most one is called the dentate, then the eboliform, the globose, and the fastigal. d. How are you going to remember these? We have a little saying—“Don’t Eat Green Frogs” i. D for dentate ii. E for eboliform iii. G for globose iv. F for fastigal e. This is going from out to in (DEGF) f. Another thing that you may have noticed here is that the dentate nucleus looks like the inferior olivary nucleus and it probably gets its name because it looks like a dental impression. If you ever had an apple and you stuck your teeth into it, it would make an impression in the apple or if you had wax or something and pushed denture Neuro: 2:00 - 3:00 Scribe: Ashley Brewington Wednesday, February 10, 2010 Dr. Nicholas Cerebellum Page 3 of 9 into wax it would make a mark and that mark looks like the mark of teeth so that is probably why it is called the dentate nucleus. g. The dentate nucleus is the outflow nucleus for the neocerebellum. h. The eboliform and globose are the outflow nuclei for the paleocerebellum. i. The fastigal nucleus is the outflow for the archicerebellum. XIII.Mollaret’s Triangle [S13] a. Now the dentate nucleus also along with the inferior olivary nucleus, actually make up two corners of a triangle called Mollaret’s Triangle. b. If you remember where are we here? (top left) That is the midbrain. Within the midbrain there is the red nucleus that contains a lot of iron. c. This triangle, if we were to start within one of the inferior olivary nuclei like this one, the opposite dentate nucleus and then go back to the same side as the inferior olivary nucleus to the red nucleus, those are the three corners of Mollaret’s Triangle. d. The three sides are the olivocerebellar pathway, going into the inferior cerebellar peduncle and entering the cerebellum. e. The outflow of the dentate nucleus is the superior cerebellar peduncle which crosses over. f. Finally the red nucleus going down to the ipsilateral inferior olivary nucleus, that is called the central tegmental tract. g. Why do you need to know that? Especially those of you who are going to be working in people’s mouths for a living, you may see a very strange thing in someone where they open their mouth and you see that their palate is jumping and the patient will complain that they hear this clicking noise in their ear and might wind up going to the ENT doctor and perhaps they couldn’t figure it out. If you open the person’s mouth, and look and see the palate jumping it is called the palatal myoclonus. When you see it, it means that there is a lesion in this pathway. Most likely a hypertensive lesion or diabetic lesion which would result in a lacun if you remember my last lecture. Usually we see it in the central tegmental tract, this pathway going from the red nucleus to the inferior olivary nucleus. Another thing about the palatal myoclonus that is unique, is very rare, but what is unique about it is one of the only movement disorders that does not go away with sleep. As a result, these people are driven crazy because they hear this clicking noise and can’t even sleep. Some people who have tremor and other movement disorders, once they can get to sleep the abnormal movements stop but this one does not stop. So something for ya’ll to know. XIV. Cerebellum: Projections to deep nuclei [S14] a. Again, as we’ve said the lateral hemispheres will project to the most lateral nucleus which is the dentate nucleus. b. The region of the vermis and the area around the vermis, is where the trunk parts are on the homunculi, that is the paleocerebellum and those cells synapse on the eboliform and globose nuclei or interposed nuclei if you want to put them together. c. The floculonodular lobe synapses in the fastigal nucleus. XV. Peduncles [S15] a. Here are some sections of gross specimen as well as slices to remind you again that the cerebellum is attached to the brainstem by these three columns on either side which are the cerebellar peduncles. b. You have a superior cerebellar peduncle, an outflow tract going north for the most part although there is an exception to the rule which we will tell you about later. c. The cerebellum since is has to do with the coordination of movement, it needs sensory input from the periphery, from sensory nerves in your limbs which will file into sensory pathways in the spinal cord and then go to the cerebellum and most of them will travel through the inferior cerebellar peduncle because that is the first peduncle you come to as you are traveling up to the brain. This makes since that most of that information will go into the cerebellum where the inferior cerebellar peduncle. d. The middle cerebellar peduncle, its major function is a conduit so how the cerebral/motor cortex can influence the cerebellum. e. Again, the motor cortex and the cerebellum work together and as you will see in a second, the cerebellum will talk to the cortex and then the motor cortex on its way down is the corticospinal tract will send collaterals off to talk to the cerebellum. XVI. Brainstem, dorsal view [S16] a. Alright, so looking at a different aspect this is what the brainstem looks like when the cerebellum is removed. b. You see these same three cerebellar peduncles on either side and their cut edges. c. To orient you, this is the caudal and this is rostral. You can see the colliculi here in the midbrain and down here this is in the medulla. Most of this area that we are talking about is at the level of the pons or the mesencephalon. Neuro: 2:00 - 3:00 Scribe: Ashley Brewington Wednesday, February 10, 2010 Dr. Nicholas Cerebellum Page 4 of 9 d. These cut slices here represent the three peduncles, the largest one being the middle cerebellar peduncle, it also goes by branchium pontis. Some of the anatomy books if you come across that name its just another name for the middle cerebellar peduncle. e. The inferior cerebellar peduncle is also known as the restiform body. f. The superior cerebellar peduncle is also known as the branchium conjunctivum. g. You really don’t need to know those names, I’m not going to test you on them but if you are reading an anatomy book that is an old fashioned one sometimes they use those names rather than superior, middle, and inferior. XVII. Microanatomy and Microcircuitry [S17] a. Lets get to the actual cellular anatomy of the cerebellum. b. It isn’t very hard, but it is a little tricky. It is a little monotonous because one place in the cerebellum is just like any other place. c. Unlike the cerebral cortex where you can have anywhere from three layers to six layers and every part of the cerebral cortex is a little different, the cerebellum is monotonous and the same. XVIII. Cerebellum: Microanatomy [S18] a. Again like I said before, you have deep white matter in the middle and all of the cells are on the surface like in the cerebral cortex. b. The cells are in these bumps called folia, rather than sulci and gyri they are called folia. c. One thing that you may see is that there is a layer that goes all the way around in pink here. You can see it even at a low magnification as this but we are showing a little higher one. XIX. Picture [S19] a. These cells are huge. Probably the hugest cells in the brain and are called purkinje cells. b. These are the major outflow cells of the cerebellum. So, those deep cerebellar nuclei that we were just talking about they get their information from these purkinje cells. XX. Picture [S20] a. A little bit of higher magnification of the cellular anatomy of the cerebellum. b. And just to orient you, on the top is the surface and on the bottom is heading toward the white matter so it is deep. c. Bottom is deep and top is the surface. d. So how many layers do you see? At first glance it looks like two, but there is actually a third layer and that is the small layer made up of very large purkinje cells. e. This is a stain, called a Nissl stain that stains proteins and nucleic acids. You do not see the cell body very much. f. In the deep cell layer there are tons of tiny cells, these are the nuclei of all these cells and are called granular cells because they look like little grains of sand I guess because there are so many of them. There are lots of little tiny cells and is called the granular cell layer. g. The second layer is these huge cells called the purkinje cells and is called the purkinje cell layer. h. Then you have another layer above that where there are not as many cells as in the other places, all of these spots represent the different nuclei of the cells but it is not as cellular as the granular layer and it is called the molecular cell layer. XXI. Picture [S21] a. Lets take a higher magnification of that interface between the granular cell layer here, the purkinje cells here, and the molecular layer above it. b. Now this is just a Nissl stain, so it just gives you an appreciation. Many times when you use a Nissl stain in the brain, all you see are nuclei and you do not get to appreciate what the cell actually looks like. c. These purkinje cells make a lot of protein and since proteins are made of nucleic acids and this is a stain that stains acid, even the cell cytoplasm stains in these cells and you can hopefully get the appreciation that there is a big dendrite that is coming out and heading north into the molecular layer and it is starting to branch out there. d. So that gives you an appreciation of what the main part of that cell looks like, but in the turn of the century there were two neuroanatomist that won the Nobel Prize for developing a new staining technique using heavy metals of gold and silver. One guys name was Golgi and the other guys name was Cajal, one Italian and the other a Spaniard. e. Previous to this, many people had the idea that the brain was just a reticulum, a bunch of cells that talk to one another but not really separate entities. f. Using these stain techniques it showed that there are individual cells like this one but they are quite exotic in how they look. g. The Nissl stain gave you an idea of the main body of this cell, but the silver stain actually shows you what the whole cell looks like. Neuro: 2:00 - 3:00 Scribe: Ashley Brewington Wednesday, February 10, 2010 Dr. Nicholas Cerebellum Page 5 of 9 h. The Purkinje cell has a hug cell body, notice that going down to the white matter there is an axon heading toward one of the deep cerebellar nuclei to synapse in the nuclei, but then it has a huge fan-coral like or bush like in profile and on the side very skinny that is all the dendrites. i. Why do we need this? We need it because the outflow of this cell has to get a lot of information from a lot of different places, so as a result it increases its surface area so it can communicate with a lot of different cells. j. To orient you, these are a couple of folia and here is one of the surface here. This is also double stained with a little bit of Nissl so you can see everything that is bluish here is the granule cell layer, and you can see the purkinje cell here, and then the big dendritic tree of the purkinje cell goes into the molecular layer. XXII. Cerebellum: Microanatomy [S22] a. If you did a stain for purkinje cells you can stain all of them and not just one of them. b. Basically showing the same thing, the granule cell is below and the huge purkinje cell with its processes going into the molecular layer for all these connections. XXIII. Picture [S23] a. There is one other cell that you need to know that is hidden here. It is hidden in the granule cell layer and it is named after one of these Nobel Prize winners that developed this stain, Golgi. b. It is a larger cell than the granule cell and it is called a golgi cell and is in the granule cell layer. c. It is a little tricky in that in the purkinje cell layer there are just purkinje cells, in the granule cell layer there are mostly granule cell but there are also a few of these larger cells called golgi cells and we will explain in a minute how they talk to one another. d. In the molecular layer, there are also a couple of little cells—the basket cells and the stellate cells. e. Those are our players, basket, stellate, purkinje, golgi, and granule. f. You need to know these cells and how they talk to each other which we will talk about in a minute. XXIV. Cells and Fibers [S24] a. Here is your purkinje cell in red and its big dendritic tree is going into the molecular layer. b. In the molecular layer, you have two cells: interneurons, stellate and basket. Both of these cells talk to the branches of the dendritic tree of the purkinje cell. c. What is the difference between the two of them? d. Stellate cells like to talk to the branches while the basket cell likes to talk to the cell body itself. I remember this basket—B body cell, body—B so I kind of remember it that way. e. Again the stellate cell talks to the branches and the basket cells talk to the body. f. Now again, do you see the axon coming off of the purkinje cell? This is the main outflow of the cerebellum. g. What about the inflow? Information coming into the cerebellum? That is shown in green here where you have two types of cells, the mossy fiber and the climbing fiber. h. The way to remember this is that the climbing fiber climbs on the branches of the purkinje cell and come from one place, the contralateral inferior olivary nucleus (part of Mollaret’s Triangle). i. All of the other input that comes into the cerebellum comes in through mossy fibers. j. You have another one here which is called a parallel fiber, this is not an input fiber but it is a fiber that comes off of the granule cell and shouldn’t really be in green so do not let it confuse you. k. The two input fibers, information coming into the cerebellum, are the mossy and climbing fiber. XXV. Climbing Fiber on Purkinje Cell [S25] a. Just to give you an idea of how the climbing fiber climbs, here is a Nissl stain and in red showing the cell body of a purkinje cell. b. One of the mossy fibers has been injected with a dye and all of its processes light up in black here and outlines the entire network of all of these branches here. It is not like one little fiber comes in and makes one synapse, it almost coats all of these branches. All of these bulbs there are all little buttons that are going to be synapsing. c. Clearly, they are really like moss on a tree so really the mossy fibers climbs on these branches and pretty thoroughly as you can see. XXVI. Cerebellum: Microanatomy [S26] a. This is a really nice slice that shows you the dynamics of the cells and how they talk to one another. b. I really like this one, I like things in color too because it helps me remember. c. If you want to study one slide for the different connections, this is a good one. d. We can start anywhere, but lets start with the purkinje cells shown in red. You can see that they have an axon that goes down and those are going to be the main outflow of the cerebellum synapsing on one of the deep cerebellar nuclei. e. The climbing fiber is going to come in and climb on those branches. f. The mossy fiber will come in and it primarily talks to two cells—the golgi and granule cells through specialized endings called a glomerulus which I’ll show you in a second with an interesting anatomy. They make a loop there, how they talk to one another. Neuro: 2:00 - 3:00 Scribe: Ashley Brewington Wednesday, February 10, 2010 Dr. Nicholas Cerebellum Page 6 of 9 g. One thing to take an aside and explain one other thing that I think is important is the neural chemistry. The neural chemistry of the cerebellum is very similar to the neural chemistry of the basal ganglia. Both of those structures are primarily GABA producing structures. What is GABA? It’s one of the most common, inhibitory neurotransmitters of the brain. GABA is the brake of the brain. Glutamate is the gas, GABA is the brake. Just like the motor cortex is your main motor output that allows you to move around, if you can remember it is like a bull in a china shop this is where the bull is the motor cortex with two leashes on it that keep it going through without knocking anything over. One leash, the GABA leash, is the basal ganglia and the other GABA leash is the cerebellum. Just like in the basal ganglia, all of the cells here produce GABA except one. In the basal ganglia it is the subthalamic nucleus and in the cerebellum it is the granule cell. So all of these cells are inhibitory except for one—the granule cell, but there are a lot of them. h. What do granule cells do? Granule cells makes glutamate so they excite everybody. They send projections that excite all other cells in the cerebellum. i. And one of the things that it does is send a fiber called a parallel fiber which starts out perpendicular and make a T, so as you can kind of imagine like a telephone pole it goes up in the sky and then the wires go in this direction and those wires are the parallel fibers. Parallel fibers are fibers of the granule cell that is going in the molecular layer and exciting all of the cells that it comes across which are purkinje cell fibers, the basket cells, and the stellate cells. It also stimulates the golgi cell and then the golgi cell will inhibit the granule cell. So it is a ying and a yang with those two cells. j. Like I said before, in the molecular layer you have two cells, the stellate inhibits the branches of the purkinje while the basket inhibits the cell body of the purkinje and you can see that there color coded if you follow them all. XXVII. Diagram [S27] a. Like I said, the ending of the mossy fiber is an unusual structure called a glomerulus. b. It gets its name from the glomerulus in the kidney, it is a little ball. c. The mossy fiber comes up into the granule cell layer and ends in this weird shaped ball and in here the golgi cells and the granule cells put their paws in there and that’s where all of the synapses occur. XXVIII. Figure 14.9 [S28] a. Even to look at it more like an EM froze picture, you can see that all of these little indentations are where all of the little buttons are being connected from either a granule cell in red or a golgi cell in yellow. b. This is called the swollen nerve ending of the mossy fiber is called the glomerulus. XXIX. Cerebellar Connections [S29] a. Here is another way to look at the same thing. Probably what you should be able to do is draw this picture so you can understand who talks to who and how they are all connected. b. How do you start? You can start here. c. Put the purkinje fiber in first, its axon is going down to the deep cerebellar nuclei and its dendritic tree is going up into the molecular layer. d. Then you put in your two input fibers—your climbing fiber which is going to climb on the tree of the purkinje cell and the mossy fiber which is going to end in the glomerulus which is going to excite the granule cell. e. The granule cell sends its telephone pole up and the telephone wires are going to be parallel as parallel fibers which will excite the purkinje cell fiber. f. So then, the next level of complexity after you have drawn this is to then add these. Again, everything in green is glutamate and in red is GABA. g. Then you can put the golgi cell in, again the golgi cell also sends its fibers into the glomerulus and excites the granule cell that then sends a projection up into the molecular layer where the granule cell can excite the golgi cell and then the golgi can inhibit the granule cell. So it is kind of like a loop, arguing with one another. h. Then you put in the other two interneurons that are in the molecular layer—stellate and basket. What do they do? Well they both get excited by the parallel fiber coming from the granule but the stellate is going to inhibit the tree of the purkinje while the basket is going to inhibit the cell body (think B-B). i. The last thing to put in here is to remember that you have a deep, cerebellar nucleus and that the purkinje cell is the main output through the deep, cerebellar nuclei but there always has to be, they have to be excited too. All the fibers that come in excite the deep, cerebellar nucleus whether is be the dentate nucleus or eboliform or whatever. j. You should be able to draw this picture. Draw this first then add those, then add that, and you got it. XXX. Cerebellar Cortex: Microanatomy [S30] a. Here is another way to draw this if you like boxes. b. Basically, it is the same picture just with boxes. c. Again, color coded where green is glutamate excitatory and red is GABA inhibitory. d. You have five cells that you have to account for. You need to know what they do, who they talk to, and who talks to them. Neuro: 2:00 - 3:00 Scribe: Ashley Brewington Wednesday, February 10, 2010 Dr. Nicholas Cerebellum Page 7 of 9 e. If you can draw this picture you have all those answers. XXXI. Cerebellar Cortex: facts [S31] a. So, the incoming signals are excitatory. b. Most of those are mossy fibers, but there are also climbing fibers coming in from the inferior olivary nucleus. c. Most of the local communication in the cortex is inhibitory, GABAergic. d. The granule cell axons are called parallel fibers. Those are the wires coming off of the telephone pole. They go parallel to the folia, and this is why they are called parallel fibers. e. Just like in the basal ganglia, there are other fibers that come in there that are modulating chemicals. In the basal ganglia the main modulating chemical is dopamine. f. In the cerebellum the main modulating chemical is noradrenaline coming from the locus ceruleus if you remember that from the pons. g. There is also a serotinergic into both the basal ganglia and the cerebellum coming from the raphe nuclei. h. There are homunculi that are drawn on the surface of the cortex that should help your remember a little about function. XXXII. Afferents, Efferents, and Functional Organization [S32] XXXIII. Functional Subdivisions of Cerebellum [S33] a. Let’s talk about function. b. Here is your color-coded archicerebellum in blue, paleocerebellum in pink, and neocerebellum in green. XXXIV. Cerebellum: Functional Organization [S34] a. Sometimes these are referred to by other names and to complete the chart (see Slide 8): i. Archi: vestibulocerebellum ii. Paleo: spinocerebellum iii. Neo: cerebrocerebellum b. Archicerebellum since it has to do with your inner ears and such is also known as the vestibulocerebellum. c. The paleocerebellum is also known as the spinocerebellum because there are pathways through the vestibular nuclei that you can get down into the spinal cord to talk to the muscles of the trunk. d. The neocerebellum is going to go north to talk to the motor cortex, so this is also known as the cerebrocerebellum. e. You need to know both names, okay? You need to know that the archicerebellum when I say it is like saying the vestibulocerebellum? You understand? You need to know both names. XXXV. Picture [S35] a. Where does all this information start from? b. The information starts from the periphery. c. Receptors that tell the brain about position or tone and you can see this is striated muscle with muscle spindles which send some of this information from the brain. XXXVI. Cuneo SCT, Rostral SCT, Dorsal SCT, Ventral SCT [S36] a. They get to the brain by way of these spinocerebellum tracts and there are four of them that you need to know. b. Two come from the legs and two come from the arms. c. This shows them very nicely in this Netter’s drawing. d. The two that give information from the legs are called the dorsal and ventral spinocerebellar tracts. e. The two that send information from the arms to the cerebellum are called the rostral and cuneo spinocerebellar tracts. f. Out of this group, one of each has a relay nucleus that you need to know. XXXVII.Four Spinocerebellar Tracts [S37] a. This summarizes it nicely, this little chart here so if you can memorize this will tell you everything you need to know about the spinocerebellar tracts and how they get into the cerebellum. b. Those are your four. c. These two are from your leg (dorsal and ventral SCT). d. These two are arms (rostral and cuneo SCT). e. Most of them enter by way of the inferior cerebellar peduncle. f. One of each of this group of legs and this group of arms, has a relay nucleus. g. The relay nucleus for the legs, you may remember it. Have you ever heard of Clark’s column before? Okay, you have wondered what the heck is that. You know how to memorize it but you don’t know what it is. Well, it is a relay nucleus for one of the spinocerebellar tracts and it is primarily the dorsal spinocerebellar tract. h. There is a similar situation for the arms. This is called the external cuneate nucleus. That is the relay nucleus for the cuneo spincerebellar tract. i. Here is the little trick of how to remember that two of the pathways. See wouldn’t it be nice if all of this information is coming from the spinal cord, why shouldn’t it just all come from the inferior cerebellar peduncle? Neuro: 2:00 - 3:00 Scribe: Ashley Brewington Wednesday, February 10, 2010 Dr. Nicholas Cerebellum Page 8 of 9 That would make it simple. Well, it would make sense because it is the first cerebellar peduncle you get to, but no some of the information had to go all of the way up to the superior cerebellar peduncle and go in that way. j. The two tracts that do not have the relay nucleus go up to the superior cerebellar peduncle. This one doesn’t have a relay nucleus, and there it is. This one doesn’t have a relay nucleus, and there it is. k. This one actually comes in through both. l. So if you can memorize this chart here, this is everything you need to know about the inputs, how you get there, where the information comes from (arm/legs) and which one has a relay nucleus and which on doesn’t, and finally what is the relay nucleus called. XXXVIII. Spinocerebellar Tracts [S38] a. In the spinal cord, this is where the ventral and dorsal spinocerebellar tracts are. They are on the most distal surface of the lateral funiculus of the white matter of the cord. b. Since this is a section of the thoracic spinal cord, what is that nucleus in there? That nucleus is Clark’s column. Clark’s column is attached to the dorsal spinocerebellar tract. c. This is why it got its name because the dorsal spinocerebellar tract is dorsal to the ventral spinocerebellar tract. That’s why they named the two of them that way. XXXIX. Clark’s Column (T1-L2): DST Relay [S39] a. But again, in the thoracic spinal cord from T1-L2 you have this column of cells called Clark’s column and it is a relay nucleus for the dorsal spinocerebellar tract. XL. External Cuneate Nucleus: CSCT Relay [S40] a. While in the rostral medulla, the relay nucleus for the cuneo spinocerebellar tract is called the external cuneate nucleus and that’s its location. XLI. Don’t forget the flocculonodular lobe… [S41] a. Do not forget the flocculonodular lobe. b. Again it has connections with the inner ear and also goes through the medial longitudinal fasiculus to actually coordinate your eye movements. c. So coordination of eyes and ears. d. Very, very rudimentary stuff. XLII. Picture [S42] a. And this is a nice section through pons that actually shows you the two floculli. b. See the little flippy flops on the side connected to the nodulus which is in the middle. c. This thing that I’m looping here, that’s the fluculonodular lobe. d. It’s not very big but that’s the archicerebellum, the most rudimentary part of the cerebellum. XLIII. Cerebellum: Functional Organization [S43] a. Here are some of the things when stuff goes wrong, how certain parts of the cerebellum are more involved with certain functions than others. b. So, your vestibulocerebellum (archicerebellum), is mostly involved with balance and eye movements. XLIV. Cerebellum: Problems [S44] a. You can see the various ones here. b. As it becomes more complicated, such as dysmetria for example, able to do fine motor movements and when we can’t do that and cannot touch the target it has to do with—remember where the homunculus is and the fingers are—they are way out in the neocerebellum which is also known as the cerebrocerebellum. c. There are some other things, ataxia, which is generalized clumsiness and that the whole cerebellum is involved with that. Whether you are clumsy in your eyes or clumsy in your hands or clumsy in your trunk. d. When you have cerebellar disease, everything goes. XLV. Ipsilateral Cerebellar ataxia due to the “double cross” [S45] a. Finally, the last thing that you need to know is this pathway which we call the double cross. b. This pathway explains how the cerebellum defies the law of the brain. c. The law of the brain is one side of the brain controls the opposite side of the body. d. The cerebellum is the same side of the body. e. How does that work, well if we start out in one neocerebellum. One neocerebellum will exit by way of the superior cerebellar peduncle, this pink line represents the midline, and will synapse in the ventral lateral and ventral anterior nuclei of the thalamus and go up and talk to the motor cortex. f. This is our corticospinal tract, and you remember the corticospinal tract right? How it comes down—first it is in the internal capsule, then the cerebral peduncle, then the pyramidal fasicles, then in the pyramid, then in the decussation of the pyramids it comes back to this side. g. So what this is trying to show is that there no cerebellospinal tract. You do not see any arrow coming out here and going down, there is no reason to do that. You already have a motor pathway that is called the corticospinal tract. Rather than going down the neocerebellar goes up to talk to the motor cortex. Neuro: 2:00 - 3:00 Scribe: Ashley Brewington Wednesday, February 10, 2010 Dr. Nicholas Cerebellum Page 9 of 9 h. One thing you also notice here is that on its way down, the motor cortex sends out little collaterals to the pontine nuclei within the pons and to the pontine fasicles in the middle cerebellar peduncle. That is how you get back to the neocerebellum that you started out in. i. So, the left neocerebellum talks to the right corticospinal tract and then on its way down that corticospinal tract sends collaterals to talk back to that neocerebellum on that same side. j. But it is a double cross because this is the cross once and then as the motor cortex comes down there is another cross. k. That explains why if you get a lesion here, it causes problems on the same side. l. So we should be able to again, draw this picture out. m. That is it except for a little question if you were paying attention. n. Question: what is the name of this cell? i. Granule cell ii. Stellate cell iii. Golgi cell iv. Purkinje cell o. Answer: Golgi cell p. I realize we ran a little bit long, but it is a complicated part of the brain and we got it all in one lecture and I appreciate your attention. Thank you very much.