all right now that we have a better understanding of the brain let's move downwards through the spinal cord in this chapter we're gonna cover the spinal cord structure how its mental designed we're gonna look at these little things here that come out on the side these are spinal nerves here and come out on the side and then we look at this stuff well we look a bunch of stuff that goes on on the inside of the spinal cord right in here we look at one of the things we look at is is is tracks those on earth fibers that connect the brain to the spine or to the rest of the body and so they'll go up and down tracks and up tracks and down tracks and then we look at automated responses the body has that they do over and over again the same way and those are described in reflexes from there we talked a little bit about nerve plexus I'll tell you what's that all about when we get there and then we get into these nerves that come not out of the spinal cord but they come out the cranium the brainstem and from there we finally touch on the part of the nervous system that deals with keeping our system in homeostasis remember that thing where the inside of the body collar stays maintains an equilibrium even though outside stuff changes when we look at the spinal cord it largely consists of these tracts or these that consistent that have pathways in them which are basically nerve fibers connecting the brain to the peripheral nervous system so some of these tracts the blue ones here go up there are the a sending tract and then some of them go down and those are the descending tracts descending has motor function in them which is doing things and a sending has sensory function in them which is feeling things bringing information into the brain on the side of the body we have these spinal nerves here on the side 31 pairs on each side a31 that come out of the cord laterally and feed the whole body so those are spinal nerves and then in the lumbar region right here as well as the cervical region right here we got an area that is a little thicker and that is an area that harbors nerve cell bodies and tracks that go into the upper and the lower extremities so therefore they need to be a little bit there's more going on in those areas the cord goes well from around here is more or less for a min magnum time or place all the way down to about l1 or l2 where it forms this tip see this tip right here that's that tip that tips known as the conus medullaris it's a cone sort of thing and after that tip the rest of the vertebral canal those nerves just those spinal nerves just come a cold down or actually their spinal roots nerve roots they just go down and then wherever they need to go exit and go to the body they go to the body there that area here is known as the cauda equina and the cauda equina what that means that means horse's tail in I guess latin that is the reason why this vinyl cord stops before spine stops is because when we develop the nerve grows less quickly or less extensively than the spinal vertebral canal does but this is a good thing because what we can do now we can actually go in this area here and take a needle and get some cerebrospinal fluid coming out of that area and then we can analyze that for you know see what's up with the fluid is it infected or not is there a problem with it or we can of course also inject substances into that area maybe look at a little bit more the spinal nerves they come out between two vertebra in what we call an intervertebral foramen so in termina in between and vertical means vertebral so it's a hole for any means all that content that is made by two vertebra stacked on top of one and order within the sacrum further down in the bot area we have the sacral foramen or foramina plural because those are just holes in the sacrum the sacrum is fused vertebrae you could see that right here they're fused vertebrae together so the nerves does come out in the in the back here and then there's some that come out in the front here this is a kind of an interesting chart what we can see here we can see the that the areas of the spine we see the vertebrae and then below here we see the description of C 1 to C 8 which is right here and of course immediately go like wait a minute we had seven cervical vertebra you don't have eight cervical vertebra and that is correct that's where you can see that the c1 the c8 indicates actually spinal nerves and not vertebrae and so this chart is a little bit misleading with that so you want to be careful for that mistaking that but I like the rest of it the color is nice I like the coloring a lot but this is in the in the cervical spine then we have eight cranial eight cervical spinal nerves that come out of that part of the spine and the reason why it's 8:00 and not 7:00 is because the first one comes out above c7 and then we count them down above the world over off the world of above the world until we got to c7 and the c7 spinal nerve comes out above the vertebra but the c8 comes out below the c7 vertebra and then everybody else is always named after the vertebra above which means the nerve comes out below it so then we have 12 thoracic spinal nerves we have five lumbar spinal nerves there's a lot of traffic and then we got a few sacral and coccygeal they're not even listed on here and that brings it up to about 31 this chart here is also kinda nice because what you can see here with the callers on the person you can see the section that each nerve controls in terms of the skin so they call that a dermatome it's a skin area that's supplied by one spinal nerve that's kind of cool now with that let's go a little bit which I say closer in the looking little ball microscopically and we are we are there slicing a spinal cord through it and we have this common op right here so when you look at the text here the spinal nerves are derived from the anterior and posterior dorsal roots or roots which only then carry motor or sensory nerve fibers so what that means is when you look at and you follow this spinal nerve right here we follow the spinal nerve into the vertebral canal into the intervertebral foramen through them to receive a foramen you go and then the spinal nerve splits in a part in the front and then to part of the back and then a part that goes to the front of the spinal cord here's the spinal cord the nerve that goes into the back portion is known as the posterior or dorsal root and the posterior dorsal root here is blue and that usually means it carries sensory nerves blue is often indicated for sensory in the nervous system and so the dorsal root only carries sensory nerves into the spinal cord and then most of them go up to the brain for processing and understanding what all that means that we just felt or what came at us and then on the other hand in the front we gonna get this other branch and that's known as the anterior or ventral root and that goes in the front of the spinal cord and only carries motor nerves in there and those are the nerves that actually bring the energy back out of the spinal cord they don't go in the energy itself the nerve flow itself so the sensor brings their own flow into the spinal central nervous system and the motor branch brings it out of the central nervous system this here is an interesting thing oh let's look at it this up because that's where it's labeled right here there is a little swelling on the backside in the dorsal end and that's known as the dorsal root ganglion and that's actually cell bodies you see that little dot right here that cell bodies of all those nerves that bring the electricity and the impulse into the central nervous system and so all a lot of those cell bodies they're all grouped here of all these different nerve fibers and collectively they get a swelling going on and then you can wrap that swelling and it is more protected than if these were all cell bodies by themselves so that's the dorsal root ganglion and then after exiting the last thing here we need to talk about when we get here see this is the spinal nerve and right after we have the spinal nerve created we exit the spinal column through a table column we go and split again into array my that goes to the back musculature and at this point that called RAM at this point and one that goes to the front of the body and the viscera the Front's usually much bigger because there's more going on in the front and extremities also go through the front so that makes more sense but those Ram I when we compare into roots the roots are things that come right out of the spinal cord and they are either sensory or motor nerve information and the RAM I are after the spinal nerve and they carry both sensory motor so they're actually mixed nerves there just which pathway do we need to go to which muscle in which organ the spinal cord itself looks quite symmetrical you could see there is a right side here and a left side here and we split that in the front we have a deep deep deep deep fissure remember the word fissure means deep groove that goes all the way almost to the center of that and that's known as the ventral median fissure and in the back we just got a little indentation so we're gonna call that like we did in the brain a little value Valley that's a sulcus right there internally maybe look at the butterfly shaped grey matter so well actually let me back up so internally then we have these two structures we got this inside thing that looks like yeah they call it like a butterfly kind of looking thing and then we got the outside part and the inside part is grey matter the outside part is white matter the grey matter is going to be cell bodies that is kind of like in the brain in the brain itself except in the brain the cortex is on the outside shell but that's sensible because in the brain the information needs to go from the cortex down to the body or up from the body and so it makes sense that the cell bodies around the outside in the spinal cord the cell bodies are going to be more internally located because the nerves coming in most of those fibers need to go as tracts up and then of course down the spine and so those are on the outside and cell bodies internally they're more internally are just sort of small integration neurons for processes that a lot of processes that happen as as reflexes that stay at the Steindl code level and so they're more inside and on outside so structurally that makes more sense it's a little hard to explain that for me right now I guess but that butterfly shape we can group that those nerve bodies we can group them into a section that's in the posterior side or dorsal neurology often uses that old world or we got a lateral side or a lateral horn see they call these horns and then we got one that's in the front that's ventral or anterior and the nuclei in those areas are specific in the back we have sensory nuclei on the side in the lateral horn we have a autonomic nuclei and in the front part we have the somatic motor nuclei you might have managed me you might have questioned what is this hole here in the inside that hole here in the inside is - you can see it up here the central canal and the central canal carries cerebral spinal fluid