you so let's continue now with our spinal nerves and I wanted to introduce the two motor components in your ventral root your ventral root if you recall was coming from your anterior horn cell it was coming up here and this would be our ventral root but I wanted you to know that there was something other than just the what we call the alpha efferent is the somatic motor component coming from the anterior horn so this would be a alpha etheric fiber coming from that cell but there are gamma efferent which are smaller and they also will go out over your ventral root and go out with your spinal nerve eventually and these are muscle spindles does anybody ever seen a muscle spindle in a tissue sample they're they're beautifully designed what are they for they're a stretch receptor but I just wanted you to know that there were two kinds of fibers going in your ventral root now let's take a cross-section of our just put it here a cross-section of a spinal nerve and we'll start with just the nerve fibers getting the cross-section of them and these then would be nerve fibers and they'll be covered with connective tissue the connective tissue surrounding a single nerve fiber is called what you know endo maryam n donor IAM so around each one of these single fibers that could either be a ferret or etheric so our rest color is the end o Maryam and these are gathered together with connective tissue which will gather them in bundles so what are you gonna call these hairy narium right Perry Nuri I'm just around again Perry narium and then the whole group of fibers are surrounded with heavy connective tissue giving us the what kept you know I'm right so when you are detecting and you pick up a nerve you're picking up out here this will this whole thing then could be just a cross-section let's just take the ulnar nerve so you see how well it's defined in here when you study pharmacology certain drugs will penetrate some of these some will not so one learns different things about this particular structure so now another term I want to introduce the term Plex I have you heard of plexus Plex I you have several major Plex I have only good a mansion to get I take no whole weight so a Plex high that's plural plexus singular we have the brachial plexus and we have the lumbosacral plexus Lumbo sacral so now you know where they are why do we need these Plex I because we've added appendages so when the nerves are going to go out they're going to recombine as they leave the cord and form a plexus there are many divisions of these Plex eyes but we're just going to introduce the concept to you so we've recombined spinal nerves to make flex I so roughly we could say let's go c5 c6 c7 and c8 and t1 those are all coming out individually but they can combine into different nerves and the one that I'm going to give you will combine all of them it's going to go out like this like this like this this and this and give us a single nerve that's a Plex I and that particular nerve that I've developed here will be the radial nerve this obviously is in our brachial plexus because that's recombined for the brachial plexus c5 to t1 and the radial nerve will go to the extensors of the forearm extensors forearm so what's going to happen when you cut it how are you going to know that you've cut the radial nerve tell somebody to salute instead of doing this they'll do this right you have what's called wrist drop because you have nothing to extend your wrist right you've cut the radial nerve so a wrist drop if you cut the medial nerve on the anterior surface is also a combination of c5 through t1 and the medial nerve then we'll be dealing with flexors does anybody ever damage the medial nerve some people will use their hand for a hammer medial nerve comes right to the surface there will damage it what can't you do if your medial nerve is damaged you can't make a fist a complete fist can't make this actually it's it's since sometimes these two ladder fingers are not involved but you can't do at least with the first three but it gives you an idea of why the they have to combine these as these cells these muscle cells are migrating out they form a different pattern they can't just do like the thoracic cavity does just come straight around right all right so that's our Plex I the next we want to do is what happens when you injure the nervous system or a nerve nerve a spinal nerve does anybody enter the spinal nerve anybody cut them nobody so this will be injury now the degree of degeneration after you've cut a nerve will depend on location degree of degeneration depend on location what do I mean by that here I have my nerve cell with its axon and I cut it at a what happens when I cut it a usually the cell will die you're that close to insulting your soma if I cut peripherally or distally that be we have several things that can occur but what we're going to do is follow first degeneration and then regeneration so let's take a we'll make a new nerve cell here and we're going to cut it this way and we have my land around it we'll just put on two segments of myelin and we'll put some down here it'll be on the fiber on the proximal end love cut will have degeneration back to the first node of ranvier degeneration back to first node of ranvier and we know that we've damaged this proximal part by changes that are taking place in the cell body so in the cell body in the soma the process of chroma Thomas have you heard of chrome italics is chroma Thomas occurs chroma Tallis this is in the injured nerve cell and what do we see with chroma Thomas how do we know this particular nerve is damaged well first the soma will take in water so it will swell soma swells that swelling will then displace the nucleus so the nucleus becomes eccentric nucleus eccentric and the missile substance which is normally fairly equally distributed throughout the cytoplasm the missile substance then will go to the periphery with the swelling missile do periphery all of this is taking place again the soma so your nerve cell instead of looking this way with missile dispersed all throughout you'll have a cell which is considerably larger the missile will be over here and in the periphery and the nucleus will be eccentric over to the side so set three characteristics of knowing whether you've got a healthy nerve cell or not now as we come back to our cut we've taken this part our proximal part chroma Tallis is here degeneration back to the first node of ranvier in the distal segment what will happen in the distal segment well the first place the axon will break up just little beads of axon left so the axon breaks up and the Schwann cells multiply so you're going to increase the number of Schwann cells out here so that they've got a Schwann cell lined tube Schwann cells cells multiply so if you don't have any scar tissue where your cut was and as the soma recovers that will send out sprouts from the axon cross the gap one of them can find your swan tube and go down and make contact with the target so with regeneration the proximal axon sprouts and one of them will find the Schwann tube sometimes you have trouble and they get all mixed mixed up in the gap here and you form a neuroma none of them can find the pathway sometimes if scar tissue comes and builds scar across here a surgeon can cut out the scar and put in a Dacron tube so when the sprout comes it'll follow that little tube and get into the proper Channel so there are ways to help how fast is it traveling once it's in the Schwann tube it can travel as fast as three to four millimeters per day that's fast what's the most rapid growth of a nerve fibers that we know that I know at least in the animal kingdom in the deer antler you know the deer shed their antlers every year and they've got that get the velvet all re innervated it's highly sensitive it can go about five millimeters there I always think someday somebody's going to go analyze and find out what substance is in the ganglion that allows that to grow so fast and use it with human beings when they damage their cord because it's really something someday somebody will do it alright so that gives you an idea of what we mean by regeneration but let's say that you've cut a neuron but you don't get chroma Tallis why not you're given some slides to study and you have no chroma Tallis's yet you know you've cut the neuron so if I have why no chroma Tallis after a nerve cut well here we have our nerve cell here is its axon here's some myelin very diagrammatically placed and this nerve is cut and you still have a perfectly healthy nerve cell why because axons can send out branches branches of axons come out just where they can between Schwann cells in a node of ranvier so I'm going to bring out a branch from this axon here going in the same direction yes apparent axon but this one's cut but we have what's known as a collateral a collateral that's a branch from an axon and it can go in the same direction or it can go back up here can they send or D send but that's the reason you can have no chroma Tallis when you've cut a parent nerve fiber because of collaterals did you know that the greatest input to your cerebral cortex are collaterals from pyramidal cells that are leaving your cortex this is cortex it's not cell going out but it's also sending back up collaterals the greatest input from all that's coming all over your body the greatest input is from pyramidal cell axons collaterals pyramidal cell collaterals which are axons but they're coming from a parent cell so you can figure that one out for the dynamics reinforcement what's it doing is that's what happens when we repeat constantly who knows but I thought that was fascinating and that was only finally ten or fifteen years ago not too long ago so now let's go back to our spinal cord and look at white matter last time we had formed what was happening to our gray matter in the spinal cord smile cord might matter we've seen that come from the marginal layer we know it's going to be peripheral in the cord so all around the periphery will be white matter we'll find that it's divided into let's put the L and a so the white matter is grouped into what we call funicula white matter forms groups of fibers which are funicula and the funicula are broken down into specific functional groups called fascicular sic our functional groups within funicula so as I showed a slide last time of multiple sclerosis that was up here in our posterior funiculus this is the posterior funiculus between the midline and over here so posterior funiculus so when you're reading slides you're saying degeneration you don't just say a white matter you say posterior funiculus you know exactly where you are so this one's going to be the lateral funiculus so what does that allow this one to be anterior but they're useful landmarks and I'm going to use one for an illustration I'm just going to take since the same sensory modality is in the whole of the posterior I'm going to take the posterior to give you an illustration of what a fasciculus is in a funiculus so if I take my cord again there'll be two fascicular in the posterior funiculus so media will have the fasciculus gracilis fasciculus Priscilla's as Priscilla's does grass hole mean pardon slender it's a real compliment give somebody how grassle you look today right it's slender so it's a slender one the lateral one is fasciculus pune otis fasciculus pune artists and whom here means when shape this is wedge-shaped so it gives you an example but here we have two fascicular why separate because the fasciculus gracilis is coming from the lower part of the body lower body which makes sense as you're bringing in sensory information you bring it over to the midline so as we get to the upper body it can come to the outer portion so this would be upper body what kind of sensations is it bringing what we call conscious proprioception right now think of your feet you could see them down there you're not moving you know exactly where they are proprioception position in space right when we get to the cerebellum you'll get unconscious proprioception that goes on every time you take a step you got to know where your feet are but you don't want to be thinking about it so you turn it over to your cerebellum but when you want to think about it that conscious proprioception so the sensory modality carried by these fibers up to the cortex is conscious proprioception very important try yourself out at night when it's dark see with you know where the light switch is all these kind of things it's fun it's good training for you so that gives you an idea of what fascicular are within fasciculus now the whole white matter is filled with fascicular and we're going to take an a sending pathway today and a descending pathway just so you get the general idea now I'm going to give it to you very briefly not all the ramifications just so you see the basics I'm taking pain and temperature as my ascending pathway it so beautifully laid out an embryo logically how it develops is amazing so we're going to take an ascending pathway and the sensory modalities will be pain and temperature how you get pain up to consciousness because we've got to come from the periphery out here and get up to your cerebral cortex when you took your shower this morning how did you know whether it was the right temperature or not if you didn't have this pathway you'll scald yourself right this is letting you know pain and temperature why pain well pain sensing is essential to your survival letting you know when you've got something that's too much essential to survival but it's also an enemy when you get to be older and you've got terminal cancer and no medication will handle the pain when you have intractable pain pain is an enemy with intractable pain you're lucky you get a little problem and you take tylenol or something but there are times when nothing that we know will get rid of it what they'll do is go cut the dorsal roots if they have to to cut the input coming into the cord but that's pretty drastic but anyhow pain phenomenal we have all kinds of pain have you ever thought about pain not if you can help it you have pain that a sharp pain that's dull pain that's burning all different degrees of pain sharp burning dough and a fascinating study is referred pain when you have something going on someplace like appendicitis frequently had aches around your umbilicus you think you've got a problem here when the problems here it's referred so referred pain that's a major one I worked on that for my master's degree because it was after the war and the fellows were coming back without any limbs and yet their limbs were hurting and there was no limb there you had to figure out what had happened to the nerves to cause that limb to hurt when there's nothing there so it referred pain is a big area so now let's look at let's follow pain we're gonna need a whole page oh the cultural pain I think that's what's fun some people get cut and they're so vocal they just don't stop talking about it others will get cut in there so Stojko I cut myself and go on which are you have to ask your friends right no I studied this once and boy some great big massive fellows couldn't take any pain at all and some little tiny dog barely had any muscles at all get some paid just take it he was so stoic it was just amazing the difference which were you your stoic okay it's easier on your friends when you're stoic I guess alright so what we're going to do is start at the bottom of a page because we're going to bring pain in but we've got to get it all the way to the cortex so we're going to be taking different slices as it goes up alright so we'll start with our first cross section down here and then we'll have our next one coming up here and our next one up here and since we don't have much room we're going to have to move over and take the cortex up here because that's our eventual destination so this will be a cross section of cord this will be another cross section of cord this will be a cross section through thalamus and this will be up to the you have a central sulcus here we call central sulcus on our cerebral hemispheres and we're going to bring in sensation to the post central gyrus so our pain and temperature is coming up to this part of your cortex post central gyrus so we're trying to come in with with these a sending pathways there are three neurons there's in the pathway a primary neuron secondary neuron and a tertiary neuron so we're going to have a primary neuron and that's gonna be in your DRG what does drg stand for dorsal root ganglia we're not going to write it out anymore and the secondary neuron is going to be in the posterior horn secondary neuron the end the posterior horn where's the tertiary neuron going to be what where do all sensations go through before they go to the cortex thalamus tertiary neurons in the thalamus so when you get a quiz and you're asked that you've damaged your secondary neuron you know exactly where it is where it's going and you could hypothesize what the result would be so we're going to follow our primary neuron up so we need our DRG out here and we're coming in then cut your little finger severely you've got this pseudo unipolar cell over your dorsal root and it's going to come just to the lateral aspect of your cord I'm going to put in my notice I'm not bringing my posterior horn all the way to the surface it doesn't come all the way to the surface now if anybody can figure out why these have these patterns I don't know but it's going to come to an area out here between the posterior horn and the surface of the cord anybody know what fasciculus that is it's named after mr. lists our this will be lists hours fasciculus I remember taking my class over for the neurosurgeons once and they asked if they knew the name and he was so pleased that they knew less hours fasciculus what happens here now and this is the question why I'm not synapsing here I'm just entering and traveling up to my next segment out here why does it do that why doesn't it come right into the dorsal Horn so this axon now well a send one or two segments terribly important in figuring out lesions they send one to two segments and then it will turn and come in to the dorsal Horn and it's going to come in to an area which is called the substantia jhalak no sir this area here and this area is substantial gelatinous have you ever heard of it before no why do we have a gelatinous part of our cord here nobody knows somebody's really gone and it's a sadist we're driven by technology you get new technology to leave back all the old things don't bother to go look them up substantial jhalak no sir so in the substantial tool at no so we're gonna have our secondary neuron so we'll pick it up and it does something interesting here's our secondary neuron it's going to cross over to my lateral funiculus down in this white komiser down here and come over here don't bring it to the surface cuz it's very important it doesn't come to the surface so this is the anterior white comma sure why do I make an issue of it anterior white comma sure because there are certain diseases where the central canal boundaries degenerate and if they do generate what are they going to do they're going to cut off your pain and temperature fibers that are crossing there so it's an important landmark in your court so I'm coming over to form a track this now has to go on up to our thalamus but it's gonna ace in over here in the lateral funiculus as it goes up to where I'm going to get into the thalamus so it forms a track out here all of the fibers will be PMT payment temperature fibers so this tract is called the spinal where it's beginning the lamech tract spinal the lamech tract and since it's in the lateral funiculus it's the lateral spinal thalamic when you study this you'll find out there others I'm only giving you the very simplest this is lateral spinothalamic tract so if you have to cut the cord for any reason you don't want to cut there you'll cut off pain and temperature you've got to know what else is around there and we're going to go up and our thalamus then was I'm just going to make a little block up here on each side of the third ventricle this is going to be my thalamus and these fibers will come in and synapse and I'll have my third neuron and it has to go on up coming up to my post central gyrus and that's where you'll have most refined interpretation of pain once you get up to the cortex so when we get up to the cortex thank you refined interpretation both pain but I'll say one thing because I'm going to show a slide of it the body is represented on the post central gyrus in an upside down manner so if I have a pain in my toe my toe we'll be sending its fibers up here my face will be down here why what do we call that the upside down representation of man homunculus I'll show you a picture of a homunculus it's the motor and sensory we have to show next time going motor down we brought sensory up homunculus sensory representation of body on cortex that's again very important because you can get rid of your anterior cerebral artery which supplies this area what supplies this area middle cerebral right very important for blockage of arteries to know the position of these let's see by slides please here we have a cross-section of a peripheral nerve this is called a scanning electron microscope you can see your blood vessels you can see the individual nerve fibers that will have the endo narium then a group will have the peri neuron and the whole thing will have the EPI maryam but this could be your owner nerve look at how vascularized it is in the next one this is just to show the distribution of the nerves to the surface it's a whole field in itself dermatomes but you see what they're very clear here for this is t10 to 1987 in the thorax but when it comes to the arms they're different you'll have t2 in here and you'll have t1 here because you have Plex I up here which are recombining the nerves as they go to your limbs in the next one and these are just normal nerve cells filled with Nissel filled with healthy nuclei if we cut the axon then this close it'll die but what you'll see first is swelling peripherally displaced this'll and eccentric or peripheral nucleus next one and this is the chord with the fasciculus Kuni artists here fasciculus gracilis here and we're following here substantial gillette Nosa here but not this would be your lisara's fasciculus out here in the next oh and then we'd have whoops I'm sorry can we go back I'm sorry I could use that same slide back please is it possible if not no back no back there thank you now here's your lateral spinothalamic tract you see it's out here but there's a spinocerebellar out here so you don't want to have cut through here you'll have to get rid you have to make the decision do you want to get rid of silk cerebellar input to reduce pain by cutting a spinal thalamic input so you need to know if you're going into neurosurgery the position of all of these in the next one and then this is our real cord we'd have our ELISA our security and then we climb up to the next one and come in to your substantial gelatinous across over in this anterior white comma sure and come on over into the lateral spinothalamic tract and a send in the next one now these are real sections of brains so we've got thalamus here so we're coming up to specific nuclei within the thalamus to have our third neuron and from there we're going to go out through the internal capsule through the corona radiata up into our sensory cortex in the next one and this is showing them this is our post central gyrus here here's our central sulcus so sensory is getting post central gyrus and the next one here's our homunculus you'll have toes way up here at the top coming down lots of hand representation the biggest representation will be hand and face but why is face right-side up in the rest of the body upside down next one this oh this will be for next lecture because we've got to come back down again alright we'll stop there you