now let's go back and look at our spinal cord I gave you two pathways that were essentially a sending just to review them for you let's take this if you recall we filled up the posterior funiculus this was our posterior funiculus with just one modality it was kinesthetic sense this is our posterior funiculus just reviewing for a moment before we bring in the descending these are ascending paths get you focus on the brain all of a sudden from out here bring it in and we said we had fasciculus chrysalis just repeating and Pune on us and that these were ascending pass they're carrying proprioception proprioception also referred to as kinesthetic sense and then we gave you the pathway this one I should mention to you because it's an important one since it takes the whole posterior funiculus for just one type of sensory modality it will have a dorsal root ganglia number one will be the DRG number two will be different it'll be the medulla and I just think you should know it because when you cross the bay you'll get it so I believe the medulla for this path and number three will be what thalamus sure they've all got to go to the thalamus before they go to the cortex all right and then we gave the lateral funiculus to see both of these here will be filled up with these are both right and left posterior funiculus so we essentially filled almost 1/3 of our white matter then we put in heater a lateral spinal thalamic track we just did at one side but I want you to get the vision these are on both sides so this was our lateral spinal the lamech tract had what was it carrying paint a temperature good for you right terribly important pain and tip and we had our three neurons for it and the first one was square first ones always to say very first one nobody want to say the drg sure and then the second one was we're frightened no that was the second one for the proprioception in the posterior funiculus this one it's an exception where is it that's correct and where is the substantial at no sir terrific good for you I gave them dorsal horn and specifically substantial no my students here take this all casually and then I see them on campus when once they're over there and they said my gosh everything you said we're getting over here too and they use it and so it is important substantial jhalak no sir and the third one was where it's always yeah following us just begin to reason with it begin to use it you will when you start having problems then you'll remember all this so now we will take all of these from the thalamus to the cortex and do you remember the sensory ones where they were going on the cortex post central gyrus right and this was our post central gyrus post central gyrus good for you so we've got sensory up to the cortex now we want to have a response we've got to take motor back down again so let's start with our descending path and these will be motor and will have two of them will have first one is called cortical bulb our corticobulbar and what does that mean you'll find with these paths that you the first word in a path tells you where it begins so this is going to begin in the cerebral cortex and you'll say what in the world is the bulb are they used to call the brain stem the bulb and that's why these tracks are going from the cortex to the brain stem and the modern derivation of brain stem this will include the midbrain and a hindbrain the part that are in the main stem not the cerebellum and so corticobulbar tract and an example would be since it's going to cranial nerve nuclei those two cranial nerve nuclei and let's just take the fifth cranial nerve nucleus now who couldn't remember what's the motor component of the fifth cranial nerve nobody dude you chew your breakfast this morning did you think what would happen if you didn't have this nerve in fact muscles of mastication sure muscles of mastication so this will be coming from the cortex down to the nucleus from the fifth four muscles of mastication then the other track will be the cortical spinal tract so from its name it's obvious it's going to go from the cortex to the spinal cord and that's the major one for the rest of your body so we're going to follow it we were just introducing cortical bulb are these two run together some of the time not always but they leave the cortex together one and two leave cortex together so where are they leaving what part of the cortex are they coming from we took sensory to post central gyrus we're going to take motor from precentral gyrus sometimes these work and sometimes they don't so we're going to follow the cortical spinal tract and it's going to originate in the precentral gyrus so here's our central sulcus and we're going to have a gyrus just in front of it and that's our precentral gyrus can you picture yours in your brain I mean you felt all over for your bones and your muscles how much of you transferred this to your brain I mean you can sort of see you're going to central here pre central would be in front of it post central behind alright so now let's follow this we've got to get down to the spinal cord so we've got a lot of brain to go through I'm just going to take off this woman use this drawing to show how we're going to take sections coming off so we're going to sort of expose our midbrain a little bit more than its exposed and then we come down come to our hind brain there's our cerebellar not here and then our medulla coming here and our foramen magnum and our cord so we want to get started with a section through our precentral gyrus take a coronal section through so a will be what we do we need a whole page so begin at the top of the page because we're going to be taking this down through the segments put some gyri here and we'll put in the basal ganglia as we've seen it there's a representative here so this will be our pre central gyrus these will be our representative of the basal ganglia for landmarks do you remember what basal ganglia did for you modifies your motor behavior keep it smooth and coordinated and then let's start now with our pyramidal cell up in the precentral gyrus it's going to be the origin of our cortical spinal tract we have lots of pyramidal cells up here and their axons then are going to descend they have to go through the internal capsule so I confine in the apex area of the basal ganglia and what have we developed here all of these axons in here I'm just going to put X's here what do we call the mass of white matter between the cells up here and the cells down in the basal ganglia corona radiata it's white matter and it's often affected with disease so they talk about the white matter of the cerebral hemispheres the corona radiata so where I put C it's only white matter between these cells and these cells so this equals the corona the radiating crown radiata clinically it's used a lot and then we come down to the area here this will represent part of the internal capsule as these fibers are condensed here fibers going to and from the cortex are all condensed in here I'm only giving you one set of fibers so in red I've put internal capsule for cortical spinal tract because you will learn eventually the blood supply of this whole area very important you see break a blood vessel here and you're paralyzed these are your main fibers going down so let's now take the midbrain section where are these fibers going through the midbrain so we put our colliculi let you know or colliculi level midbrain what's the name of our former central canal here aqueduct good and down here on the ventral surface these are motor fibers so you're going to see on ventral not dorsal this was sensory up here this was visual auditory sensory this is motor will see our paths coming through here down here in our cerebral peduncles but in the middle there are lots of other fibers going down I just have to do it this way because I don't have the dimensions but you realize this is a continuation down and we pick them up here in the cerebral peduncles these are cerebral peduncles and our next area will give the upper medulla this was midbrain so you learn the characteristics of each part of the brainstem that's the beauty of it no two parts are the same real challenge so my next drawing will be of the upper medulla who can tell me what the ventricle will be here over the medulla for sure fourth ventricle and will my motor pathway and the medulla be up here or down here up or down which is dorsal which is ventral this is dorsal this is ventral will motor be dorsal or ventral thank you bye that is so fun too methyl you're learning about your brain you've got bleeds know the difference so we have what are called in they take a parental shape here these are still the same fibers but at the medulla level they look like this so if you saw something that looked like that what would you call it a pyramid yes these are pyramids so down here they call it the pyramidal tract if you want to but it's still the cortical spinal tract but just going through the medulla all right what happens to it next this was upper medulla by the time we get to lower my dalla it does something different so we've got whoops lower medulla looks something like this this is Laura medulla woops can you tap that please thank you what's happening in the lower medulla to this cortical spinal tract it's deciding to cross you think we understand anything about this brain why in the world to kind of wait belt gets down here and then cross so we have what's called the decussation of the pyramids from the pyramids and the cross so this represents the crossing or decussation of the pyramids but only 80 to 90% of them cross what do the others do they continue to stay where they are and I'll mark them in a different color here those in the medial area here will stay here in green these are uncrossed so now our next section because what we've taken here we've taken one here in midbrain this was a then a was up here up here then B will be midbrain we've taken it through here and C this is B and this is C down here upper medulla would be upper medulla and then D is lower medulla so we get them from all directions so you become familiar with them so our next one will be e will be spinal cord we've reached our destination you will be spinal for it and it's become an old friend now yeah familiar with it Oh stare your horn and tear your horn you know we're not in the thoracic chord how do you know that we're not in thoracic chord a lateral horn right we didn't have time to give you a lateral horn but if this were a thoracic cord you have very thin horns because you don't have much muscle mass around your thorax but you also have a lateral horn so it differs if there's thin horns and a lateral horn I just slip this in at the moment and why do we have a thoracic card that has lateral horns because this is the connection of the CMS with the ANS this is for the ANS when we get to the MS we'll get to that but I just wanted you to see if you see one of these like this you know you're not interested but we've now crossed and we've brought these fibers up to this position so who's gonna tell me in which funiculus in the chord will this group of fibers descend in the posterior in the lateral or in the anterior right and tear you only the uncrossed see they're here they're gonna stay there but I look at what I drew here they're up here where are they going to be over there lateral good for you right so we're going to have them coming down here in the lateral funiculus so this is still our cortical spinal tract but we could add a definition to it where it is a location so we'll call it the lateral cortical spinal tract and this one becomes the medial cortical spinal tract or anterior so now it's time because we're our destination is the anterior horn cell where are we going to find the anterior horn cell here or here one or two - sure those are your anterior horns so there you'll find it let's make an anterior horn cell so we can bring in this cortical control multipolar cell here with its axon going out over the ventral root so now we'll have fibers that will leave our lateral cortical spinal tract and come over and synapse with our anterior horn we'll call this one one will be sent out directly with anterior horn so is this going to be for refined movement or crude movement what do you guess fine right by a move when it comes to rectly to the anterior horn cell so this is for fine movement for more generalized movement my fibers going to come over to an interneuron talked about interneurons and then down to your anterior horn cell so for general movement not this fine movement we come into an interneuron and then to the anterior horn cells and we did this one in blue now you say well what about this other ten to twenty percent that hasn't crossed yet but it's down here in our anterior cortical spinal tract well those fibers these will cross at the segments in the cord where they're going to leave the cord these will cross in segment of cord where exit cord let's play so they will eventually further down I'm not going to draw a full picture for them they'll come in and cross but that's a fascinating system in itself why in the world is it doing all this alright now we want to talk about what are known as upper motor neurons and lower motor neurons because when they're damaged they put about bring about completely different symptoms so our upper motor neuron will be our criminal cell that's an upper motor neuron because we've seen we have two neurons in this tract its axon will come down to an anterior horn cell where we'll have the lower this is anterior horn cell is our lower motor neuron and as neurologists they have to know the difference in what happens if I cut here have an automobile accident my cord gets cut as it's in a collateral cortical spinal tract and what are going to be the symptoms versus a cut that I get down that impinges on my anterior horn cell so this is called an upper motor neuron lesion and we'll see various clinical symptoms the first is called flaccid paralysis flaccid paralysis and what is that that's a very weak or feeble paralysis not a strong one it's a weak feeble paralysis shortly after the injury it'll change that's one characteristic it'll change to a paralysis a paralysis and the paralysis will be a continuous contained paralysis but it's it's not a strong one but it's a continuous one continuous paralysis the next one is that the loss of superficial reflexes loss of superficial superficial reflexes in the mail that'll be the loss of a cremasteric reflex you know where your cream a steric muscle is it's the muscle that's attached to your testes and when it gets too cold the test this moves up towards the abdomen when the cream a steric muscle pulls it up so the cream a steric free nasty right reflex there's a superficial one you just stroked this muscle and the test this will ascend in other words it comes out of the cold so that's a superficial reflex for you have an exaggeration of deep tendon reflexes exaggeration of deep tendon reflexes obviously these are easier to test you just tap your patellar tendon and if you have an upper motor neuron lesion instead of just giving a chart it flies up so if you're testing for it stand aside because you get kicked in the chin if he really has an upper motor neuron lesion but I saw one over at UCSF and the neurologist this is when I was a student we were visiting and they said well would you like to see an upper motor neuron lesion sure and so he tapped and and he didn't do anything tapped and he's so embarrassed because this is supposed to demonstrate turned out she had on woolen underwear that was that thick under her slacks that wasn't even getting through to her tendon so to let you know as young physicians if you're tending to be sure you're tapping the tendon and not all the underwear all right exaggeration deep tendon reflexes that'll be the knee jerk and the last one is a positive Babinski a positive the big escape slips whoops trying to hurry here we've got so much to cover it no we're not making it okay positive Babinski and what is this you stroke the sole of the foot your toes are usually like this if you have an upper motor neuron lesion the toes will fan out so stroke so foot but you have to stroke it with something not just with your hand when we saw this same doctor he used his keys just took a key instructor and a toes went out so you have to really get the impulse through still Saul a foot and the toes will fan so that's a positive Babinski so the shure ones that are easy to test would be the positive Babinski and the exaggerated deep tendon reflexes that love to know that you're on the right track for an upper motor neuron lesion because the lower motor neuron lesions are fairly obvious and easy for you to figure out the lower motor neuron lesion this is going to be we've damaged our anterior horn cell where is it going skeletal muscle right remember your skeletal muscle peripheral nuclei so it's going to muscle and we've cut it so what will we see loss of reflexes we have no function from the muscle loss of reflexes with time the muscle will atrophy you need your nerve connection to your muscles for them to stay healthy you cut them muscle dies atrophy of muscles and what happens you get paralysis so what used to be the well-known disease that attacks these polio the polio virus the virus polio myelitis and you see the people without the muscles in the leg if it attacks just the lumbosacral anterior horn cells but it gives you an idea of why it's important to know your pathways their connections with the nerves and the symptoms related to them so with that we'll move on to the cerebral hemispheres and as we said the cerebral hemispheres account for about eighty-five percent of your brain I mean they're that big massive amount and the cerebral cortex will be the few layers of cells that cover these hemispheres what this cortex mean means bark so these are the outer layers of cells on the hemispheres they're only in your occipital cortex is only a millimeter thick it's very thin its thickest frontal cortex is thick thicker it's up to four millimeters occipital down to one so we've talked about the cortex because we've talked about the bones on the outside so we know what our lobes are we've had them but we didn't get them at much detail we'll see how much detail we can give you because some of you will want to go into embryology and find out how these nerve cells migrate to where they are how they know how to get there how they know what transmitter to give the only decisions that these cells have you feel tired just thinking about him I mean all that time I was using all those cells for my motor activities right for talking that had to be synchronized with hand movement which was cortical spinal versus cortical ballpark it's so phenomenal so now we're cerebral hemispheres we're going to take the frontal lobe frontal lobe is the largest behind your forehead and we've already had parts of it but I want to give other terminology which is used clinically so we've had our precentral gyrus right so this is our precentral gyrus and now we're going to introduce Broadman terminology because this is used frequently Broadman lots of people have given numbers to the cortex so that you can talk about area two three four but broad months has been one that has stayed so he has the numerical designation of cerebral cortex so precentral gyrus is going to be area four talk about area four you know exactly where you are we said the precentral gyrus gave rise to the cortical spinal tracts but other areas that we're going to develop will participate will will mention those as well let's go first this is our refined motor for pre central then we go to promoter promoter is six so it's for more generalized most less specific motor where I like it is on the medial aspect what is six doing on the medial aspect it still it's called supplementary motor on the medial aspect of the hemisphere where we have our corpus callosum in here we have our central sulcus here then this would be area six on the medial aspect for behind it this is supplementary motor what's it doing for you it's visually planning your motor activity before you ever execute how many of you are divers how many have ever been off three meter boards yes we were always on those as kids that's what you do growing up in Southern California you did your flips you did all of this but before you left the end of that board you planned what you are going to do watch the Olympic divers they stand there before they ever go off and twist and do everything that's premotor supplementary planning isn't wonderful I mean they do it you do it when you're on the basketball court I mean you're deciding how much whoops you've got I'm on the basketball court when I supposed to be finished but this is supplementary motor for pre for planning motor activity fascinating area I'm going to give you one more I'm going to give you very eight these are for frontal eye fields because we know visions all way back in the occipital but here we are in the frontal these are four conjugate eye movements we've talked about those before so we're seeing a lot of this frontal lobe is motor but this is both eyes working together so let's look at our slides and we'll finish this next time all right here's our cortex as we see it from the side we'll have our central sulcus we'll be coming down here whose central sulcus post central gyrus precentral gyrus and then we just gave the promoter area and then the frontal eye fields here in the next one and this shows that you'll have a we said a sensory homunculus on your post central gyrus well you have a motor homunculus on your precentral gyrus again I asked you why is this right-side up and the rest of the body is upside down nobody gave me an answer yet in the next one and this is showing the corona radiata here's my cortex out here on the gyri and sulci the axons have to get all the way down to either as cortical ball bars to cranial nerve nuclei on the brain stem or cortical spinal anterior horn cells in the next one and this shows good your your basal ganglia I'm sorry this is an unstained brain so you can see how dark they are just because of pigmentation and blood vessels here was your card eight they're always your putamen and your Globus pallidus the fibers are coming from here they're coming down by the genu of the corpus callosum here and going on to the next one next one please and down here with our cerebral peduncles colliculi aqueduct substantial all midbrain but this part of our pea dunkels will be our cortical spinal tracts traveling down you break a blood vessel here you'll get paralyzed next one now we're down at upper medulla and you'll learn someday what the characteristics are this nucleus here will tell you it's upper medulla but here are your pyramids pure tracks coming down next one and now they're crossing and there it gets sort of messy when they cross it's not as pretty a picture as it usually is anybody tell me what group of cells these would be do you remember that tract gracilis these would be the nuclei for the gracilis just to see if you could figure things out here we go so we're going to cross let's see the next one it'll be less crossing it's hard to get one that does it just like we do on the blackboard but all this mess is crossing in the next one and here we are down in the cord so we're going to be out here in the lateral funiculus with our lateral cortical spinal tract and our anterior cortical spinal tract in the anterior funiculus here were our posterior tracts and the posterior funiculus in the next one and we didn't get as far as we wanted to so I can't go on with the rest of the gyri on this let's see one more do I have one more where was that it yes this it will be visual cortex we'll get it next time it here's your supplementary motor cortex up here for planning your activity you