Lab 6: The Nervous System

welcome to lab six which covers the nervous system this is a very busy lab with a lot of main objectives and here are some of those major topics for this lab number one you'll be looking at the divisions of the nervous system that is the central versus the peripheral nervous system you'll be learning about the structures of a neuron and also about the structure of Nur nerves and how those are different you'll be taking a look at the structures of the spinal cord you'll better understand reflexes you'll be looking at the structures of the brain you'll be naming both cranial nerves and peripheral nerves as well as learning a number of muscles that are controlled by those nerves you'll be looking at structures of the eye and you'll be looking at structures of the ear in addition at the end of this lab you'll be doing dissections of both a brain and eye specimens so let's get started with this material so the nervous system pretty easy to divide the nervous system anatomically it's broken into two main sections the central nervous system the CNS and the peripheral nervous system the pns pretty simple the central nervous system is composed of the brain and of the spinal cord anything that is outside of the brain or the spinal cord that is anything that's in the periphery is part of the peripheral nervous system this is going to include all those nerves that you're going to be learning so all the nerves that you're learning uh what these nerves are or what nerves are they are bundles of axons bundles of axons that are traveling distances within the body and they are contained within a connective tissue enclosure also part of the pns are ganglia gangan is singular ganglia is plural and ganglia are a group a swelling a cluster of neuron cell bodies and you'll see these in the upcoming diagrams looking at this visually the colors aren't that dramatic but the central nervous system is shown in sort of a tan color and again that is the brain and the spinal cord anything outside of that shown in yellow are the nerves and the ganglia in this diagram you will see the ganglia are these round little clusters of nervous tissue that are found outside of the spinal cord so let's take the take a look at a neuron so the neuron is not the most numerous of the cells within the nervous tissue but it is by far the most exciting and probably the most uh important for our conversations in this class these are the cells that transmit electrical signals and that process and uh coordinate uh your nervous system main ideas here you'll be seeing this again in lecture you'll also be labeling uh neurons in your mastering and uh pre-lab assignments the neuron is quite different from the cell the prototypic cell that you learned about in the early chapters of the course we think of a spherical cell well the neuron is quite different from that the cell body is what you probably think of as being the cell it has the nucleus in the center and it has a very dark staining nucleolus but there are a number of processes in a neuron and just like in the skeletal system a process is something that sticks out so we see all of these processes that are sticking out of this cell body most of those are dendrites now you know that dend from our vocabulary means treel like and it is something that's small so these small tree like or Branch like structures that are sticking out of the cell body now the other name for the cell body is the Soma and that is how this particular image is labeling that cell body and there is also going to be a more substantial process just one of them called an axon and here you see the axon is significantly longer at the end the axon does Branch off and even along the middle of the axon there can be a significant branch that would be considered an axon collateral and the red arrow here is telling us that electrical information travels away from the Soma down the axon this image I should add to but um the information the electrical information regarding the dendrites information comes in through the dendrites so electrical information is going to enter into the cell body through the dendrites and is going to leave away through the axon a away axon away note that along the axon and only along the axon there are some additional cells that are protecting the Axon these additional cells I'll put them in a different color these additional cells are Schwan cells okay they are Schwan cells and you'll see one here and one here and one here now these are separate cells they have their own nucleus they have their own metabolism they create a fatty lipid Rich substance called myelin and that myelin creates a sheath a wrapping around layer after layer after layer around the axon in between those Schwan cells there are small gaps and those small gaps were named after a person and they're called the nodes of Ron V so that is a capital R Ron V nice French word at the very end of the axon there are some nonmyelinated extensions these small extensions have three different names by which they go one that's labeled here terminal arborizations terminal at the end arborizations on Arbor Day we plant trees so the same idea these small Branch like extensions at the end of the axon the other name for these t tendria same idea tilo at the end dend little trees at the end remember we know tilo means last or and we saw that the last phase of tilo phase and you'll also see these um tendria or terminal arborization just referred as axon terminals so any of those terms are used interchangeably at the very very Tippy end of any of these extensions there are little swollen areas called synaptic knobs and those synaptic knobs are where chemicals are released from the neuron that initiate or sustain or even inhibit electrical signals that carry from one cell to the next these synaptic knobs can either be interacting with a muscle telling that muscle to contract these synaptic knobs can release chemicals that tell a gland to secrete something like your salivary glands to make spit or your lacrimal glands to make tears or maybe your pancreas to secrete some digestive enzymes these synaptic knobs can also synapse with other neurons and send a chain reaction down a series of neurons remember synapse sin means to gather APS we learned in our vocabulary means to fit or to fasten so a synapse is simply where two things come into very close contact they fit or they fasten together and that is we'll see this more as we study the nervous system and how it interacts with other cells so that was a prototypic neuron neurons come in type different types um one there are sensory neurons as the name suggest these are neurons that pick up Sensations found in your skin found around your viscera uh when you feel full um your stomach stretches that sends a sensory signal to your brain to stop eating when your bladder fills it sends a signal as it stretches that you need to find the restroom when something is hot or cold or vibrating or painful on your skin and that is picked up those Sensations are picked up by Sensory neurons the other term for that is aent aant you know from the vocabulary that AF means toward and fair means to carry so what we're talking about is carrying toward signals toward the central nervous system so these Sensory neurons pick up information and they send it toward the central nervous system now I will in my lectures in my presentations I will say aant to really emphasize the a but please know that this term is usually pronounced as afferent right afferent but I find that it it goes by so quickly and as we're learning we don't hear that a clearly so aent on the bottom there are also motor neurons motor neurons are the ones that are also called eent neurons EF going away from carrying away these are the neurons that carry information from the CNS from the brain from the spinal cord away and back toward muscles or glands these are the neurons that send the instructional information telling your body what to do after the brain has processed some information finally in between there are interneurons you know from vocab that inter means between so these these are the neurons found between the incoming sensory and the outgoing motor neurons they are found 100% completely contained within the CNS within the brain or spinal cord they account for the vast majority of our neurons here I report 90% other sources may say 95 or even a higher percentage of all the neurons in your body are of this type these are the processors these are the uh integrators uh these are the neurons in your spinal cord that are receiving all that sensory information making decisions about it and then sending those instructions out through these motor neurons so let's put these neurons together how does this all work notice that on the left hand side this is the peripheral nervous system in green and central nervous system is shown in blue brain and spinal cord so let's say you you've got your finger here in your skin you have lots of sensory neurons sensory receptors they picking up vibration touch pain pressure so something is triggered in your skin that information is going to travel through this sensory neuron it's actually going to go into the spinal cord so you see how we entered into the central nervous system that neuron is going to synapse with a second neuron this second neuron is an interneuron these interneurons are also referred to as Association neurons it is going to process think about that information and then it will if necessary synapse with an outgoing motor neuron notice it now it's going to leave the spinal cord and come back to the periphery and go directly to a muscle so here we see that motor neuron or that eent neuron carrying that information out to what is referred to as the eector so the eector is what is effected it's the muscle or the gland that is receiving this information so we see here that while we classify these neurons separately they all work together additionally neurons come in variations of shape and size so that previous list was their function additionally neurons come in different shapes or morphologies excuse me the most common neuron is the multi-polar neuron these are the most common uh by multi-polar what that refers to is that there are many dendrites but only one axon these neurons can have we know 10,000 plus dendrites so imagine one cell receiving signals from 10,000 maybe even as many as a hundred thousand dendrites simultaneously obviously this neuron is a it's really a huge processor right it's receiving tons of information the picture here is not even showing it as complex as it actually would be right all of those information coming into to that one Soma as we go through this unit you're going to see that the interneurons and the motor neurons are of this type so interneurons and motor neurons are both motor polar in their morphology in their shape jumping down unipolar neurons and you may also see them called pseudo unipolar same thing so pseudo unipolar or unipolar neurons these neurons have only one process one pole and you'll see them often times here here's the Soma and here is that single process coming out of that Soma that's why it's called unipolar and much of this is axonal or axonic and um these are the this is the morphology of your Sensory neurons so the sensory neurons that we're going to see in this chapter and in this unit are going to be um unipolar in their shape we're not going to worry about the anaxonic neurons the bipolar neurons um will maybe come across them but it will not be a f a focus of this course these bipolar neurons are found in your special senses that is in your sense of smell hearing and vision and as the name suggests they have two poles bipolar one is axon and one is dendr so here's a table that you can fill out and use this what is the function location and to what class do they belong are they multi-polar or unipolar so fill this table out as a way of pulling all this information together so we've been describing a neuron a neuron is a cell you have hundreds of millions if not a billion of these neurons in your body but we also hear the term nerve and I want to make sure that these two words mean something very different to you because they're very different but they tend to get thrown together you'll hear that neurons are also called nerve cells and this gets confusing so here is a diagram of a nerve okay so it's a connective tissue encased structure it is composed on the inside of of axons okay axons and those axons are grouped in bundles called fices so this is identical architecture to muscle remember in muscle we had individual muscle cells wrapped in groups called fices same idea in a nerve um in a nerve the outer layer of connective tissue is referred to as the epin nuum the groups of facies are surrounded by a layer connected tissue referred to as the parinari and each and every individual axon is surrounded not only by the myelin but also is surrounded by a thin layer of endon nuum this is connective tissue so it looks exactly the same and in fact uh for the same reason those connective tissue layers Prov provide a space for blood vessels to travel through remember these axons are surrounded by Schwan cells and these Schwan cells need their own oxygen and uh nutrient Supply so they must be nourished and so these blood vessels traveling through the connected tissue layers of the nerve are vital to keep that nerve alive we've all had our elbow on the table and felt our our hand go numb or our pinky go numb and it just turns out that the oner nerve comes right around the electron and as you keep your elbow on the table the blood supply to that nerve gets interrupted and that causes a dysfunction a numbness to that nerve let's take a look at histology of a nerve so in this picture here the nerve is going in and out of the screen you are looking this is is just a portion of a larger nerve you are looking at fices so each of these that I'm circling is a fasle it is a group of axons okay now another term for axons are nerve fibers let's make sure that makes sense to us back in the connective tissue conversations a fiber was the same as a protein right a fiber was like a collagen fiber an elastic fiber in muscle a fiber referred to the entire cell muscle cell was also called a muscle fiber but in nervous tissue when you see I'm nerve n when you hear about a fiber in nervous tissue a nerve fiber is only a portion of the neuron it is just the axon so what you're seeing in a fasle is a bun of these nerve fibers or axons if you look closely here you can even see I'm going to change colors you can even see that these individual nerve fibers are surrounded by a white layer and that white layer is the myin right so you can see that myelin wrapped around each of those we also see these large blood vessels right so again we we can see that very clearly in this hystological image from a longitudinal view taking a look we see now the nerve structure and I'm going to change colors here and try to draw for you it's a little bit abstract but I assure you that I'm not making this up right through here would be one of those nerve fibers hard to see but here's that white shadow there's a Schwan cell right here and there's another Schwan cell right here and the reason I know that you can see that there's a some cleavage there's an indentation and that is a node of Ron vaa you can see another one of these nodes of Ron VA right here you can see another you can see a few of them throughout this image and here would be another example of a node so here you're looking at a longitudinal view as a nerve is going from left to right you're looking at just a portion of it so again when you hear neuron and nerve make sure that you are quickly differentiating which one is uh referring to let's take a look at the spinal cord so the spinal cord uh we probably in your mind imagine it being bigger than it really is the spinal cord is about a typical pencil in size okay in diameter and um we probably imagine it being thicker than that bigger than that but you've seen vertebra you've seen images of vertebra and your pinky would struggle to go down the vertebral fan in most vertebra so it's not as big around as you probably imagine but it is a long cylindrical structure and another thing that is usually misunderstood is the spinal cord does not go on all the way down to the sacrum the spinal cord itself What's called the spinal cord proper actually ends at a bell L1 okay it goes down through the vertebral feram down to L1 inferior to that there's a group of nerve roots that travel down through those vertebral feram I'll come back to that coming off from the spinal cord there are 31 pairs of nerves these are the spinal nerves they arise from the regions of the spinal cord referred to as the cervical region the thoracic region the lumbar region and the sacral region there the the spinal cord is not a perfect thin cylinder there are a couple of places where it enlarges and that's in the cervical region and down at the lumbar region where the spinal cord itself tapers off and comes to an end there's a pointed like structure sort of like the sharpen pencil the tip of a pencil and that is referred to as the medular cone or in Latin the con is medular inferior to that conus medis you have the nerve roots of nerves L2 through S5 that travel down through and res resemble a horse's tail and hence its name Kata you know that term meaning tail equina you may recognize equestrian horse so the horse's tail so I've already alluded to this the spinal cord has four regions some books will also have a fifth regon they'll have a coxal region that is at the very Tippy end of the spinal cord they may refer to as a coxal region there are 31 pairs of nerves again coming off from that spinal cord and when those nerves come off the spinal cord it in four distinct areas the nerves travel as a group and a group of nerves traveling together is referred to as a plexus so we'll see these in a moment let me go ahead and name these for you or number these for you there are eight nerves that come off the cervical region there are 12 that come off the thoracic region there are five that come off the lumbar five that come off the sacral and one that comes off the coxy so that's where you get your 31 pairs of nerves then there are four regions where these nerves travel off together in the neck the cervical plexus going to the arm the bracho plexus going down the anterior thigh and leg the lumbar plexus and going down the posterior thigh and leg the sacral plexus some books will combine this and call this the lumbo sacral plexus but I'm going to keep it separate because I think there's a lot of benefit in keeping it as two separate groups of nerves so taking a look at this image then so again there is the the cervical nerves right and they're numbered C1 through C8 that's a little bit different isn't it remember that there were only seven cervical verb vertebra but there are eight cervical nerves so that's the one change in numbers there are 12 thoracic vertebra and there are 12 thoracic nerves T1 through T12 from the lumbar region there are five lumbar L1 through L5 and then there are sacral S1 through S5 this particular image does show one little nerve right there a pair of nerves those are the coxal nerves and they might be referred to as Co or co1 the spinal cord itself is ending right about here at the medular cone these nerve roots that are traveling down below that spot collectively are referred to as AATA equina and there is a filamentous u connective tissue structure that runs down let me change colors that runs down through the middle of the Kina and helps to uh hold the spinal cord down to the coxics and that's referred to as the terminal philm or the uh philm terminal in Latin spinal cords are pretty important structure and as such is protected by three distinct layers of connective tissue the outer layer the most durable is the dura mod we know from our vocab that dur means hard it's the toughest of the layers it's very tough collagenous layer um outside of that Dura is a space that you may have heard of the epidural space right on Epi on the dura and there's a lot of fat blood vessels in there so during child birth or other uh procedures where a person wants um relief from pain or surgical blocks they will go into the epidural space inject anesthetic and until that wears off that person is not able to feel from that point down in their nervous system the middle layer is a simple squamous layer so it's not very thick but it has a number of collagen fibers is associated with it that sort of looks like a spider web and therefore it gets its name the arachnoid modder below that is a space called the sub arachnoid space this space is filled with a solution called the cerebral spinal fluid CSF this fluid not only goes around the outside of the spinal cord it also travels down through the center of the spinal cord through a structure called the central canal and this fluid also has a circulation pattern and travels up around the brain as well and then finally there is a very delicate layer shrink wrapped to the surface of the spinal cord called the pamada or just the Pia it's a very delicate layer it's going to follow like a shrink WP layer every Groove and crevice along the spinal cord notice if you spell these layers from Deep to superficial it spells pad right this is a pad around the spinal cord also we'll see around the brain let's take a look at these menes plural and also for the first time you're seeing a vertebra uh with the spinal cord within the vertebral fan uh and so what we have been seeing up until now this would have been this whole opening would have been the vertebral for raymen and now we see that it's filled with the spinal cord which you know takes about half of that diameter of Theo framen let's talk first about these layers so they're they're clearly marked on this diagram so the orangey salmon colored layer the outer layer here is the dura that's the toughest layer and just above that let me change colors there's I'll make it yellow because it's well it's already yellow but I'll highlight it more so here's that fatty epidural space that is outside of the dura but still within the vertebral foramen and that would be the area that a nurse anesthesist or an anesthesiologist would be uh trying to send that anesthetic right bring that needle in between the vertebra and inject it in the that space very delicately right below that is the sub uh is the arachnoid modder in this diagram it's shown as kind of a white layer and that arachnoid mod if you notice looks like it has these dark fibers right I'm draw them here right and these these little spider web looking fibers is where it gets its name also so in this area you're seeing all this blue all this blue color in here is fluid and that is referring to I'll make it purple for now but all this blue space would be where the CSF is so that all that blue area would be the subarachnoid space and then finally shrink wrapped to the surface of the spinal cord a very delicate layer referred to as the Pam Mo not the best color let's go with some of the more obvious but I'm drinking in purple here but you can see there's just a very delicate layer shrink W right to the surface of the spinal cord and that is the PM mod when you look at the spinal cord uh well first of all what kind of vertebrae is this oh darn it it is labeled isn't it so that makes it easy it's a cervical vertebrae uh but tell me in your mind right now um if that wasn't labeled as a cervical vertebrae how would you know that it was I'm hearing you all think right I'm hearing you say hey here's some transverse foramina right and so I see those transverse feram this must be a cervical vertebrae I also see the splits minus process which is sometimes present on cervical vertebrae when you look at the spinal cord you notice that it looks like a a butterfly um you see these butterfly wings and the Butterfly shaped structure is dark matter it's the dark matter of the spinal cord uh in the nervous system we talk about dark matter and white matter dark and white and so the Dark Matter here uh the actually you'll hear it called gray matter the gray matter here is butterfly shaped in the very center of that butterfly there is a a hole and that's the central canal let's take another look at the spinal cord and this gives us a different perspective I think maybe a little bit easier to see these three distinct layers so here we see the dura modder it is the toughest outer layer the very thin um arachnoid modder underneath which there's some fluid filled space right that subarachnoid space f filled with fluid and then in this particular image the pink layer is the Pam Mo shrink wrapped to the surface notice that there's still a very rich vascular Supply traveling right along the spinal cord so the spinal cord is protected by these layers menial layers and it's not only protecting the nervous tissue but also the vascular supply to the spinal cord you can see also in this image the gray butterfly the gray matter and the gray matter of the spinal cord is broken up into three regions called horns [Music] okay so there is the dorsal horn just the back side there is the lateral horn change colors and then finally there is a ventral horn okay and you'll see this labeled over and over you'll be getting you'll become pros at this um the area that connects the two butterfly wings is called the gray commer and again in the very center there's a canal the central Canal what you're seeing off to the side in yellow are the nerves so let me also help you with your orientation the gray butterfly that you see in the in the spinal cord the wings of the butterfly always reach up and touch the back side they always reach up and touch the posterior side of the spinal cord they never touch the anterior side so that will always give you your orientation so the dorsal horn will always be the part of the grve matter that is reaching all the way up and reaching toward the back on the sides we see the spinal nerves so a nerve remember is a bundle of axons and here is the nerve we see it kind of the cling the coming together of these two branches um this region is the dorsal root and in the front we have the vental root you'll also hear posterior and anterior Roots equivalent terms and then here's a dorsal root gangion I'll talk more about that in lecture but just pointing out these structures you'll be hearing about them as we go along finally in the spinal cord there are two two deep grooves in the front in the front there's the anterior median fissure fissure is a is a Groove and on the posterior side there is the posterior median sulcus Now by convention a sulcus is a it's a it's a shallow Groove and a fissure is a deeper Groove so it just tells you that in the anterior side the groove is deeper however some books will mix and match these terms so you might see um you might see the anterior median fissure referred to as a anterior median sulcus so don't go crazy looking for a separate structure it's the same thing the white matter that goes around the gray butterfly is also broken up into three areas these areas are called columns another word you'll see for them each one is a finicula it's a fun word right f n so you'll see either the ventral column or the vental finicula you'll see the lateral column or the lateral finicula and you'll see the posterior or the dorsal column or finicula running up and down through that spinal cord are clusters of axons there's a new term here I need you to know though and that is that within the spinal cord there are no nerves instead inside the spinal cord we have what is referred to as tracks it's just a it's a nomenclature type thing so in the peripheral nervous system a group of neurons axons I should say a group of axons is called a nerve in the central nervous system a group of axons is referred to as a tract and so what we see see is that going up and down the spinal cord there are ascending tracks and descending tracks ascending tracks are the tracks the axons carrying information from the periphery and going up the spinal cord toward the brain so those are the ascending tracks and also in your spinal cord are descending tracks these are carrying motor information down which will then go out of the spinal cord and go to your muscles or to your glands the spinal cord is the main connector between your body and the Brain but there's one job that the spinal cord does all by itself that does not include the brain and that is the spinal cords responsible for your reflexes reflexes you know what they are they're they're really quick automatic involuntary reactions we usually think of them as reactions of muscles we've all watched Law and Order type shows a person is hooked up to a lot a lie detector test and uh maybe you're not aware of this but there's a lot of components to that lie detector test the examiner is asking questions and the person being asked the questions they're looking at his or her eyes looking for changes in the pupil diameter they have a monitor on their skin looking for changes in sweat they have a monitor on their heart rate seeing if their heart rate goes up or their breathing rate goes up all of those things typically will be increased if you're lying right your your heart rate goes up your breathing rate goes up you sweat a little bit more your pupils change and so these are all reflexive responses U as an example another example that you're probably very familiar with is touching a stove or stubbing your toe so let's talk about touching the stove uh you touch stove even before you are consciously aware that you are burning yourself you will quote reflexively pull back from that hot surface you'll pull back before you're even aware of it right you pull back and then you go oh man that hurts right you you pull back before you even aware of it consciously how did that happen there's this is the wiring What's called the reflex arc of the of the reflex so something in this case a pin poked your skin now you've got nerve endings in your skin uh they picked up on that pain sensation those signals traveled through that nerve entered into your spinal cord notice um as information comes into the spinal cord always goes in the posterior roote or the dorsal root and that that neuron is now going to speak with some interneuron found in the spinal cord these interneurons are going to make the decision hey that that's not good and they're going to send information out through a motor neuron always out the anterior route and in this case going to a muscle so if you were reaching out touching the stove perhaps that reflex is telling your biceps brachii or your brachialis to flex your elbow away from that painful sensation again none of this includes the brain this is happening before that now right after you pull away your brain does become aware of it and you become aware that you have burned yourself and all of that that goes on but the immediate response of a reflex here are the five steps and it does not involve your brain let's look at another reflex this is so cool you're you're walking along and with your right foot your Barefoot it's somewhere it look like and you step on something sharp so those pain receptors in your right foot are going to send that signal up to your spinal cord notice it comes in the back door and goes in it's going to speak to those interneurons and then those in neurons are going to say hey dummy you just hurt yourself go out the front side go back down this motor neuron is now going to go down to H I wonder what muscle would cause you to flex the knee that might be the hamstring group right and maybe your soaz major was involved in retracting that leg up and you would do that but what's so cool not only did you lift up your right leg but other interneurons in your spinal cord went to the other side of the spinal cord a contralateral relationship spoke to other motor neurons that now went down to your left leg and told your left leg to extend so that would be for example your quadriceps muscles right would be involved in um causing your leg to extend at the knee so this is a more involved reflex but still all of that would happen even before you were consciously aware you would withdraw the the foot from the pain and simultaneously you would extend the other foot so that you don't fall over very cool stuff and because there's quite a few synapses Happening Here in the spinal cord this is referred to as a poly synaptic reflex so just looking a little more carefully at the spinal cord again now you see the nerves are numbered C1 through C8 T1 through T12 the lumbar and the sacral nerves and then this particular image also has the plexuses labeled so the cervical plexus the brachial plexus going off to the arm the lumbar plexus and the sacr plexus note the sacr plexus is heading behind going down through that sciatic Notch and heading down the posterior thigh whereas it's hard to see here I know but those lumbar nerves are traveling down the anterior side of the pelvis are traveling down the anterior thigh as you look at the cadaveric image here you appreciate that the spinal cord you can see those um the the nerve Roots merging to make the root and you'll be seeing more of these images you're going to be learning the names of quite a few nerves now the great thing about naming nerves is that you already know most of these terms these terms the these the nerves are named either for the region of the body through which they pass or they're named for the muscle or the region that they go to so the naming of or the bone along which they travel so the naming of nerves should not be a challenge for you you'll have to take out your book make some notes but I think you'll find this to be pretty straightforward so for example the the nerves that go over to the arm uh the brachial plexus there are five nerves that run down the arm uh there's the axillary nerve H makes sense it's up in the armpit area there's the radial nerve we're going to see that it comes down and runs along the radius makes sense the owner nerve comes down runs along the pinky side again runs along the Ona that makes sense there's a nerve that goes right down the middle of all that and that is the median nerve okay right down the middle and then finally there's a nerve referred to as the muscular cutaneous which is not shown on this image now there are 20 some muscle nerve combos that you're going to be learning for example there's a separate handout for this but you're going to learn that the deltoid muscle is controlled by the axillary nerve now folks this is not that hard you've got to do some you have to do some matching up but if the deltoid muscle is sitting in the shoulder area as you know and the axillary nerve is sitting here in this area I would argue that that is not a huge stretch right for you to learn that the deltoid muscle right that would be sitting here is controlled by this axillary nerve likewise um the radial nerve right the radial nerve comes down and it goes right here right and this it's going to control your triceps brachi the muscle that's or the uh nerve that's not shown here the muscular cutaneous is going to be controlling your biceps bracha so look at that handout I think there's 26 or 27 of those nerve muscle combinations that you'll need to learn so while we're not directly testing on the muscles and Bones from the first lab exam you can't forget it you'll be applying that information as we move forward let's take a look at the brain the brain is the most complex of the organs that we have studied so far you're going to learn quite a bit about the brain um this slide is showing you what's called the functional areas of the brain that is each lobe of the brain has a number of jobs that it is primarily responsible for there are certain regions of the brain when damaged uh the person can no longer do certain things so if you were to lose a significant portion of your frontal lobe due to a stroke or to some sort of brain injury you would have def deficiencies in your thinking your memory your behavior and it's your frontal lobe that initiates your movement So when you say or when you when your brain tells your biceps brachi to move those instructions are coming from a portion of the frontal Lo If instead you had damage to your Pari title lobe loes left and right then you would probably have some issues with language and you would also have issues with touch and other sensory type of information if you had damage to your ocial lobe that would affect your site perhaps if you had damage to your temporal lobe you could have significant issues your hearing uh also some learning some feelings as well there's a lobe that's not shown here but if you were to crack open this brain along this s Fus this fissure here and look inside there's another lobe called the insula that's where your taste centers are if you were to have brain damage to your brain stem this purpley area then you would have issues with your ability to breathe or regulate your heart rate or regulate your body temperature and if instead you had issues or damage to your cerebellum you would probably have issues with your balance and coordination now there's a whole lot more that the brain does but these are the main areas uh the main jobs if you will of these regions of the brain as you look at the brain uh in a mid sagittal cut like this uh there is a number of structures that you you'll be looking at you will be naming the lobes right the frontal lobe parial lobe you'll be looking at the ocial lobe temporal lobe would be on the farest side right here when you open it up midsagittally there's a very thick band of white matter here that is the Corpus colossum there's another thick band of white matter on the bottom side that's referred to as the fornex there is an area here I'm circling this area is the thalamus right below that is is the hypothalamus so we have the hypothalamus right below the thalamus there's a large oval region in the brain stem referred to as the ponds there's also an oblong region called the medulla oinga through here and then if you imagine here's the oipal bone coming around the base of the skull everything that passes through that foran Magnum would be spinal cord there's a few more structures on here that you'll be learning but those are some of the big ones for now in addition to learning a number of the the nerves that come off the spinal cord the spinal nerves there are also 12 pairs of nerves that come off the brain and the brain stem referred to as the cranial nerves these nerves are different in that they are numbered uh when they're when uh they're either named with a name or they are numbered always using Roman numerals and you'll see those Roman numerals here 1 through 12 so if you don't know your Roman numerals it's time to learn them and specifically in this lab you will be seeing the optic nerve coming off the eye in your dissection and you're going to see the vestibular clear nerve in the ear as you learn about the ear now you are not responsible for identifying these nerves on the brain so if you flip over a brain model or look at your Atlas and your book you're going to see these cranial nerves labeled you are not responsible for identifying the cranial nerves but you do need to learn uh the cranial nerves what they do okay and in some of these cases some of these cranial nerves also control muscles so for example the accessory nerve the 11th cranial nerve you're going to learn controls your trapezius and your sternal Clomid muscles think about your shoulder muscles the ability to shrug and turn your head is controlled by one of these pairs of cranial nerves the accessory nerve or cranial nerve 11 you'll also be learning that a number of muscles in your face for example the zygomaticus the orbicularis oculi the orbicularis orus are controlled by the facial nerve and you'll be learning that the muscles that move the eye are controlled by the ocular motor the trolear and the abducent nerve so that information is coming and you'll be learning more about that in this unit as well as in lecture two more structures to be looking at today structures of the eye and then in the next Slide the structures of the ear let me just you'll also be dissecting an eye today just looking at this quickly and then you'll be digging in a little bit deeper but there are three main layers of the eye the white of the eye is called the Scara now vocabulary will'll learn later that scare means hard as you are cutting through this outer layer you will experience just how tough and hard that outer layer is not hard like a rock but very very tough the middle layer is referred to as the choid the inner layer is the retina retina retina you know reticulum you've seen the endoplasmic reticulum uh you know that retina or reticulum means a network reticular fibers and so the retina is a network of receptors that receive visual signals right visual receptors in the eye the optic nerve there it is that is cranial nerve number two that's coming off the posterior eye it's going to carry that visual information from the retina to the oipal lobe of your brain as well as other parts of your brain we see some of these muscles of the eye coming around you will be learning and did already learn the muscles around the eye this would be the superior rectus and this would be the inferior rectus muscle around the eye the lens of the eye is shown here in your body in a freshly killed specimen it would be a clear uh very Crystal Clear structure in your dissected eye it's going to be much more cloudy kind of yellow ysh in color simply because it has been sitting in the solution the outer layer covering where the light goes in is called a cornea you may have scratched your cornea before you know that that's a very very highly innervated very painful scratch to scratch the cornea in the front of the eye there's a space an area referred to as the anterior cavity and in that anterior cavity there's a liquid called aquous humor in the back of the eye in the posterior cavity there's a jellylike substance called the vitus humor so in lecture we'll talk about how this all works together but your job now is to learn the structures of the eye and then finally the ear again focusing on the structures not the physiology not how this works but the ear is broken up into three areas there's the outer ear there's the middle ear and there's the inner ear the outer ear is composed of the Pina you may also see this called The Oracle that's the Flappy part of your ear and uh I guess we'll talk about a little bit about how the ear works so the sound comes in through your Canal ear canal and hits this membrane okay you know it as your as your eard drum but we're not going to give credit for that we're going to call it the tanic membrane like the tempany and the orchestra the big drum so that tanic membrane is going to vibrate uh that vibration is now going to be transferring that Vib vibrational energy to three bones there's three three bones collectively are called the oces the first one is the malas then the incus then the stapes you'll also hear stapes so stapes or stapes these now are the last bones that you need to learn so in the skeletal unit we learned 200 bones of the 206 bones there are three of these oses in each ear so now you know all 206 bones in your body that vibrational energy is going to go on this stapes and there's an opening behind the stapes and that energy is now going to come into the entryway here this entryway is called the vestibule the vestibule you may know that vestibule just means an opening into something uh architectur talk Arch Architects talk about a vestibule in a building or in a church in your body you have a nasal vestibule an oral vestibule uh there's a vaginal vestibule and as you come into the opening of the inner ear you look off to one side you see three semicircular canals these three semicircular canals are involved with balance to the other side you now see this spiral structure called the Clea and that's where your hearing is occurring we'll deal with more details later uh the information for the semicircular canals travels through a portion of a nerve called the vestibular nerve the information for for hearing travels through the clear nerve these two nerves come together so these two nerves come together to form one nerve and that is the vestibular clear nerve and it is also your cranial nerve 8 okay so you'll see it called either the vestibular clear nerve or vestibular or or the cranial nerve number eight so at the end of this lab you're going to be doing a couple dissections each of you has a sheep brain the Sheep brain is going to have hopefully the outer layer on here that's the dura moer here is some spinal cord keep in mind that in a four-legged animal uh their their architecture is a little bit different so um in our in our brain the cerebellum uh would be sort of down below the um the loes but on a sheep the cerebellum is here right and the ocial Lo would be U would be deep to that you're also going to be having an eye and you'll be cutting the eye you'll be doing some labeling some activities you have a choice you can either after you've done your dissections lay out your pieces on a piece of paper write the structure and draw a line to it the best you can or you can take a video of pointing to each of the structures on the dissection rubric list and upload that so you'll be either uploading images labeled images or uploading a video to your instructor at the end of this lab

welcome to lab six which covers the nervous system this is a very busy lab with a lot of main objectives and here are some of those major topics for this lab number one you&#39;ll be looking at the divisions of the nervous system that is the central versus the peripheral nervous system you&#39;ll be learning about the structures of a neuron and also about the structure of Nur nerves and how those are different you&#39;ll be taking a look at the structures of the spinal cord you&#39;ll better understand reflexes you&#39;ll be looking at the structures of the brain you&#39;ll be naming both cranial nerves and peripheral nerves as well as learning a number of muscles that are controlled by those nerves you&#39;ll be looking at structures of the eye and you&#39;ll be looking at structures of the ear in addition at the end of this lab you&#39;ll be doing dissections of both a brain and eye specimens so let&#39;s get started with this material so the nervous system pretty easy to divide the nervous system anatomically it&#39;s broken into two main sections the central nervous system the CNS and the peripheral nervous system the pns pretty simple the central nervous system is composed of the brain and of the spinal cord anything that is outside of the brain or the spinal cord that is anything that&#39;s in the periphery is part of the peripheral nervous system this is going to include all those nerves that you&#39;re going to be learning so all the nerves that you&#39;re learning uh what these nerves are or what nerves are they are bundles of axons bundles of axons that are traveling distances within the body and they are contained within a connective tissue enclosure also part of the pns are ganglia gangan is singular ganglia is plural and ganglia are a group a swelling a cluster of neuron cell bodies and you&#39;ll see these in the upcoming diagrams looking at this visually the colors aren&#39;t that dramatic but the central nervous system is shown in sort of a tan color and again that is the brain and the spinal cord anything outside of that shown in yellow are the nerves and the ganglia in this diagram you will see the ganglia are these round little clusters of nervous tissue that are found outside of the spinal cord so let&#39;s take the take a look at a neuron so the neuron is not the most numerous of the cells within the nervous tissue but it is by far the most exciting and probably the most uh important for our conversations in this class these are the cells that transmit electrical signals and that process and uh coordinate uh your nervous system main ideas here you&#39;ll be seeing this again in lecture you&#39;ll also be labeling uh neurons in your mastering and uh pre-lab assignments the neuron is quite different from the cell the prototypic cell that you learned about in the early chapters of the course we think of a spherical cell well the neuron is quite different from that the cell body is what you probably think of as being the cell it has the nucleus in the center and it has a very dark staining nucleolus but there are a number of processes in a neuron and just like in the skeletal system a process is something that sticks out so we see all of these processes that are sticking out of this cell body most of those are dendrites now you know that dend from our vocabulary means treel like and it is something that&#39;s small so these small tree like or Branch like structures that are sticking out of the cell body now the other name for the cell body is the Soma and that is how this particular image is labeling that cell body and there is also going to be a more substantial process just one of them called an axon and here you see the axon is significantly longer at the end the axon does Branch off and even along the middle of the axon there can be a significant branch that would be considered an axon collateral and the red arrow here is telling us that electrical information travels away from the Soma down the axon this image I should add to but um the information the electrical information regarding the dendrites information comes in through the dendrites so electrical information is going to enter into the cell body through the dendrites and is going to leave away through the axon a away axon away note that along the axon and only along the axon there are some additional cells that are protecting the Axon these additional cells I&#39;ll put them in a different color these additional cells are Schwan cells okay they are Schwan cells and you&#39;ll see one here and one here and one here now these are separate cells they have their own nucleus they have their own metabolism they create a fatty lipid Rich substance called myelin and that myelin creates a sheath a wrapping around layer after layer after layer around the axon in between those Schwan cells there are small gaps and those small gaps were named after a person and they&#39;re called the nodes of Ron V so that is a capital R Ron V nice French word at the very end of the axon there are some nonmyelinated extensions these small extensions have three different names by which they go one that&#39;s labeled here terminal arborizations terminal at the end arborizations on Arbor Day we plant trees so the same idea these small Branch like extensions at the end of the axon the other name for these t tendria same idea tilo at the end dend little trees at the end remember we know tilo means last or and we saw that the last phase of tilo phase and you&#39;ll also see these um tendria or terminal arborization just referred as axon terminals so any of those terms are used interchangeably at the very very Tippy end of any of these extensions there are little swollen areas called synaptic knobs and those synaptic knobs are where chemicals are released from the neuron that initiate or sustain or even inhibit electrical signals that carry from one cell to the next these synaptic knobs can either be interacting with a muscle telling that muscle to contract these synaptic knobs can release chemicals that tell a gland to secrete something like your salivary glands to make spit or your lacrimal glands to make tears or maybe your pancreas to secrete some digestive enzymes these synaptic knobs can also synapse with other neurons and send a chain reaction down a series of neurons remember synapse sin means to gather APS we learned in our vocabulary means to fit or to fasten so a synapse is simply where two things come into very close contact they fit or they fasten together and that is we&#39;ll see this more as we study the nervous system and how it interacts with other cells so that was a prototypic neuron neurons come in type different types um one there are sensory neurons as the name suggest these are neurons that pick up Sensations found in your skin found around your viscera uh when you feel full um your stomach stretches that sends a sensory signal to your brain to stop eating when your bladder fills it sends a signal as it stretches that you need to find the restroom when something is hot or cold or vibrating or painful on your skin and that is picked up those Sensations are picked up by Sensory neurons the other term for that is aent aant you know from the vocabulary that AF means toward and fair means to carry so what we&#39;re talking about is carrying toward signals toward the central nervous system so these Sensory neurons pick up information and they send it toward the central nervous system now I will in my lectures in my presentations I will say aant to really emphasize the a but please know that this term is usually pronounced as afferent right afferent but I find that it it goes by so quickly and as we&#39;re learning we don&#39;t hear that a clearly so aent on the bottom there are also motor neurons motor neurons are the ones that are also called eent neurons EF going away from carrying away these are the neurons that carry information from the CNS from the brain from the spinal cord away and back toward muscles or glands these are the neurons that send the instructional information telling your body what to do after the brain has processed some information finally in between there are interneurons you know from vocab that inter means between so these these are the neurons found between the incoming sensory and the outgoing motor neurons they are found 100% completely contained within the CNS within the brain or spinal cord they account for the vast majority of our neurons here I report 90% other sources may say 95 or even a higher percentage of all the neurons in your body are of this type these are the processors these are the uh integrators uh these are the neurons in your spinal cord that are receiving all that sensory information making decisions about it and then sending those instructions out through these motor neurons so let&#39;s put these neurons together how does this all work notice that on the left hand side this is the peripheral nervous system in green and central nervous system is shown in blue brain and spinal cord so let&#39;s say you you&#39;ve got your finger here in your skin you have lots of sensory neurons sensory receptors they picking up vibration touch pain pressure so something is triggered in your skin that information is going to travel through this sensory neuron it&#39;s actually going to go into the spinal cord so you see how we entered into the central nervous system that neuron is going to synapse with a second neuron this second neuron is an interneuron these interneurons are also referred to as Association neurons it is going to process think about that information and then it will if necessary synapse with an outgoing motor neuron notice it now it&#39;s going to leave the spinal cord and come back to the periphery and go directly to a muscle so here we see that motor neuron or that eent neuron carrying that information out to what is referred to as the eector so the eector is what is effected it&#39;s the muscle or the gland that is receiving this information so we see here that while we classify these neurons separately they all work together additionally neurons come in variations of shape and size so that previous list was their function additionally neurons come in different shapes or morphologies excuse me the most common neuron is the multi-polar neuron these are the most common uh by multi-polar what that refers to is that there are many dendrites but only one axon these neurons can have we know 10,000 plus dendrites so imagine one cell receiving signals from 10,000 maybe even as many as a hundred thousand dendrites simultaneously obviously this neuron is a it&#39;s really a huge processor right it&#39;s receiving tons of information the picture here is not even showing it as complex as it actually would be right all of those information coming into to that one Soma as we go through this unit you&#39;re going to see that the interneurons and the motor neurons are of this type so interneurons and motor neurons are both motor polar in their morphology in their shape jumping down unipolar neurons and you may also see them called pseudo unipolar same thing so pseudo unipolar or unipolar neurons these neurons have only one process one pole and you&#39;ll see them often times here here&#39;s the Soma and here is that single process coming out of that Soma that&#39;s why it&#39;s called unipolar and much of this is axonal or axonic and um these are the this is the morphology of your Sensory neurons so the sensory neurons that we&#39;re going to see in this chapter and in this unit are going to be um unipolar in their shape we&#39;re not going to worry about the anaxonic neurons the bipolar neurons um will maybe come across them but it will not be a f a focus of this course these bipolar neurons are found in your special senses that is in your sense of smell hearing and vision and as the name suggests they have two poles bipolar one is axon and one is dendr so here&#39;s a table that you can fill out and use this what is the function location and to what class do they belong are they multi-polar or unipolar so fill this table out as a way of pulling all this information together so we&#39;ve been describing a neuron a neuron is a cell you have hundreds of millions if not a billion of these neurons in your body but we also hear the term nerve and I want to make sure that these two words mean something very different to you because they&#39;re very different but they tend to get thrown together you&#39;ll hear that neurons are also called nerve cells and this gets confusing so here is a diagram of a nerve okay so it&#39;s a connective tissue encased structure it is composed on the inside of of axons okay axons and those axons are grouped in bundles called fices so this is identical architecture to muscle remember in muscle we had individual muscle cells wrapped in groups called fices same idea in a nerve um in a nerve the outer layer of connective tissue is referred to as the epin nuum the groups of facies are surrounded by a layer connected tissue referred to as the parinari and each and every individual axon is surrounded not only by the myelin but also is surrounded by a thin layer of endon nuum this is connective tissue so it looks exactly the same and in fact uh for the same reason those connective tissue layers Prov provide a space for blood vessels to travel through remember these axons are surrounded by Schwan cells and these Schwan cells need their own oxygen and uh nutrient Supply so they must be nourished and so these blood vessels traveling through the connected tissue layers of the nerve are vital to keep that nerve alive we&#39;ve all had our elbow on the table and felt our our hand go numb or our pinky go numb and it just turns out that the oner nerve comes right around the electron and as you keep your elbow on the table the blood supply to that nerve gets interrupted and that causes a dysfunction a numbness to that nerve let&#39;s take a look at histology of a nerve so in this picture here the nerve is going in and out of the screen you are looking this is is just a portion of a larger nerve you are looking at fices so each of these that I&#39;m circling is a fasle it is a group of axons okay now another term for axons are nerve fibers let&#39;s make sure that makes sense to us back in the connective tissue conversations a fiber was the same as a protein right a fiber was like a collagen fiber an elastic fiber in muscle a fiber referred to the entire cell muscle cell was also called a muscle fiber but in nervous tissue when you see I&#39;m nerve n when you hear about a fiber in nervous tissue a nerve fiber is only a portion of the neuron it is just the axon so what you&#39;re seeing in a fasle is a bun of these nerve fibers or axons if you look closely here you can even see I&#39;m going to change colors you can even see that these individual nerve fibers are surrounded by a white layer and that white layer is the myin right so you can see that myelin wrapped around each of those we also see these large blood vessels right so again we we can see that very clearly in this hystological image from a longitudinal view taking a look we see now the nerve structure and I&#39;m going to change colors here and try to draw for you it&#39;s a little bit abstract but I assure you that I&#39;m not making this up right through here would be one of those nerve fibers hard to see but here&#39;s that white shadow there&#39;s a Schwan cell right here and there&#39;s another Schwan cell right here and the reason I know that you can see that there&#39;s a some cleavage there&#39;s an indentation and that is a node of Ron vaa you can see another one of these nodes of Ron VA right here you can see another you can see a few of them throughout this image and here would be another example of a node so here you&#39;re looking at a longitudinal view as a nerve is going from left to right you&#39;re looking at just a portion of it so again when you hear neuron and nerve make sure that you are quickly differentiating which one is uh referring to let&#39;s take a look at the spinal cord so the spinal cord uh we probably in your mind imagine it being bigger than it really is the spinal cord is about a typical pencil in size okay in diameter and um we probably imagine it being thicker than that bigger than that but you&#39;ve seen vertebra you&#39;ve seen images of vertebra and your pinky would struggle to go down the vertebral fan in most vertebra so it&#39;s not as big around as you probably imagine but it is a long cylindrical structure and another thing that is usually misunderstood is the spinal cord does not go on all the way down to the sacrum the spinal cord itself What&#39;s called the spinal cord proper actually ends at a bell L1 okay it goes down through the vertebral feram down to L1 inferior to that there&#39;s a group of nerve roots that travel down through those vertebral feram I&#39;ll come back to that coming off from the spinal cord there are 31 pairs of nerves these are the spinal nerves they arise from the regions of the spinal cord referred to as the cervical region the thoracic region the lumbar region and the sacral region there the the spinal cord is not a perfect thin cylinder there are a couple of places where it enlarges and that&#39;s in the cervical region and down at the lumbar region where the spinal cord itself tapers off and comes to an end there&#39;s a pointed like structure sort of like the sharpen pencil the tip of a pencil and that is referred to as the medular cone or in Latin the con is medular inferior to that conus medis you have the nerve roots of nerves L2 through S5 that travel down through and res resemble a horse&#39;s tail and hence its name Kata you know that term meaning tail equina you may recognize equestrian horse so the horse&#39;s tail so I&#39;ve already alluded to this the spinal cord has four regions some books will also have a fifth regon they&#39;ll have a coxal region that is at the very Tippy end of the spinal cord they may refer to as a coxal region there are 31 pairs of nerves again coming off from that spinal cord and when those nerves come off the spinal cord it in four distinct areas the nerves travel as a group and a group of nerves traveling together is referred to as a plexus so we&#39;ll see these in a moment let me go ahead and name these for you or number these for you there are eight nerves that come off the cervical region there are 12 that come off the thoracic region there are five that come off the lumbar five that come off the sacral and one that comes off the coxy so that&#39;s where you get your 31 pairs of nerves then there are four regions where these nerves travel off together in the neck the cervical plexus going to the arm the bracho plexus going down the anterior thigh and leg the lumbar plexus and going down the posterior thigh and leg the sacral plexus some books will combine this and call this the lumbo sacral plexus but I&#39;m going to keep it separate because I think there&#39;s a lot of benefit in keeping it as two separate groups of nerves so taking a look at this image then so again there is the the cervical nerves right and they&#39;re numbered C1 through C8 that&#39;s a little bit different isn&#39;t it remember that there were only seven cervical verb vertebra but there are eight cervical nerves so that&#39;s the one change in numbers there are 12 thoracic vertebra and there are 12 thoracic nerves T1 through T12 from the lumbar region there are five lumbar L1 through L5 and then there are sacral S1 through S5 this particular image does show one little nerve right there a pair of nerves those are the coxal nerves and they might be referred to as Co or co1 the spinal cord itself is ending right about here at the medular cone these nerve roots that are traveling down below that spot collectively are referred to as AATA equina and there is a filamentous u connective tissue structure that runs down let me change colors that runs down through the middle of the Kina and helps to uh hold the spinal cord down to the coxics and that&#39;s referred to as the terminal philm or the uh philm terminal in Latin spinal cords are pretty important structure and as such is protected by three distinct layers of connective tissue the outer layer the most durable is the dura mod we know from our vocab that dur means hard it&#39;s the toughest of the layers it&#39;s very tough collagenous layer um outside of that Dura is a space that you may have heard of the epidural space right on Epi on the dura and there&#39;s a lot of fat blood vessels in there so during child birth or other uh procedures where a person wants um relief from pain or surgical blocks they will go into the epidural space inject anesthetic and until that wears off that person is not able to feel from that point down in their nervous system the middle layer is a simple squamous layer so it&#39;s not very thick but it has a number of collagen fibers is associated with it that sort of looks like a spider web and therefore it gets its name the arachnoid modder below that is a space called the sub arachnoid space this space is filled with a solution called the cerebral spinal fluid CSF this fluid not only goes around the outside of the spinal cord it also travels down through the center of the spinal cord through a structure called the central canal and this fluid also has a circulation pattern and travels up around the brain as well and then finally there is a very delicate layer shrink wrapped to the surface of the spinal cord called the pamada or just the Pia it&#39;s a very delicate layer it&#39;s going to follow like a shrink WP layer every Groove and crevice along the spinal cord notice if you spell these layers from Deep to superficial it spells pad right this is a pad around the spinal cord also we&#39;ll see around the brain let&#39;s take a look at these menes plural and also for the first time you&#39;re seeing a vertebra uh with the spinal cord within the vertebral fan uh and so what we have been seeing up until now this would have been this whole opening would have been the vertebral for raymen and now we see that it&#39;s filled with the spinal cord which you know takes about half of that diameter of Theo framen let&#39;s talk first about these layers so they&#39;re they&#39;re clearly marked on this diagram so the orangey salmon colored layer the outer layer here is the dura that&#39;s the toughest layer and just above that let me change colors there&#39;s I&#39;ll make it yellow because it&#39;s well it&#39;s already yellow but I&#39;ll highlight it more so here&#39;s that fatty epidural space that is outside of the dura but still within the vertebral foramen and that would be the area that a nurse anesthesist or an anesthesiologist would be uh trying to send that anesthetic right bring that needle in between the vertebra and inject it in the that space very delicately right below that is the sub uh is the arachnoid modder in this diagram it&#39;s shown as kind of a white layer and that arachnoid mod if you notice looks like it has these dark fibers right I&#39;m draw them here right and these these little spider web looking fibers is where it gets its name also so in this area you&#39;re seeing all this blue all this blue color in here is fluid and that is referring to I&#39;ll make it purple for now but all this blue space would be where the CSF is so that all that blue area would be the subarachnoid space and then finally shrink wrapped to the surface of the spinal cord a very delicate layer referred to as the Pam Mo not the best color let&#39;s go with some of the more obvious but I&#39;m drinking in purple here but you can see there&#39;s just a very delicate layer shrink W right to the surface of the spinal cord and that is the PM mod when you look at the spinal cord uh well first of all what kind of vertebrae is this oh darn it it is labeled isn&#39;t it so that makes it easy it&#39;s a cervical vertebrae uh but tell me in your mind right now um if that wasn&#39;t labeled as a cervical vertebrae how would you know that it was I&#39;m hearing you all think right I&#39;m hearing you say hey here&#39;s some transverse foramina right and so I see those transverse feram this must be a cervical vertebrae I also see the splits minus process which is sometimes present on cervical vertebrae when you look at the spinal cord you notice that it looks like a a butterfly um you see these butterfly wings and the Butterfly shaped structure is dark matter it&#39;s the dark matter of the spinal cord uh in the nervous system we talk about dark matter and white matter dark and white and so the Dark Matter here uh the actually you&#39;ll hear it called gray matter the gray matter here is butterfly shaped in the very center of that butterfly there is a a hole and that&#39;s the central canal let&#39;s take another look at the spinal cord and this gives us a different perspective I think maybe a little bit easier to see these three distinct layers so here we see the dura modder it is the toughest outer layer the very thin um arachnoid modder underneath which there&#39;s some fluid filled space right that subarachnoid space f filled with fluid and then in this particular image the pink layer is the Pam Mo shrink wrapped to the surface notice that there&#39;s still a very rich vascular Supply traveling right along the spinal cord so the spinal cord is protected by these layers menial layers and it&#39;s not only protecting the nervous tissue but also the vascular supply to the spinal cord you can see also in this image the gray butterfly the gray matter and the gray matter of the spinal cord is broken up into three regions called horns [Music] okay so there is the dorsal horn just the back side there is the lateral horn change colors and then finally there is a ventral horn okay and you&#39;ll see this labeled over and over you&#39;ll be getting you&#39;ll become pros at this um the area that connects the two butterfly wings is called the gray commer and again in the very center there&#39;s a canal the central Canal what you&#39;re seeing off to the side in yellow are the nerves so let me also help you with your orientation the gray butterfly that you see in the in the spinal cord the wings of the butterfly always reach up and touch the back side they always reach up and touch the posterior side of the spinal cord they never touch the anterior side so that will always give you your orientation so the dorsal horn will always be the part of the grve matter that is reaching all the way up and reaching toward the back on the sides we see the spinal nerves so a nerve remember is a bundle of axons and here is the nerve we see it kind of the cling the coming together of these two branches um this region is the dorsal root and in the front we have the vental root you&#39;ll also hear posterior and anterior Roots equivalent terms and then here&#39;s a dorsal root gangion I&#39;ll talk more about that in lecture but just pointing out these structures you&#39;ll be hearing about them as we go along finally in the spinal cord there are two two deep grooves in the front in the front there&#39;s the anterior median fissure fissure is a is a Groove and on the posterior side there is the posterior median sulcus Now by convention a sulcus is a it&#39;s a it&#39;s a shallow Groove and a fissure is a deeper Groove so it just tells you that in the anterior side the groove is deeper however some books will mix and match these terms so you might see um you might see the anterior median fissure referred to as a anterior median sulcus so don&#39;t go crazy looking for a separate structure it&#39;s the same thing the white matter that goes around the gray butterfly is also broken up into three areas these areas are called columns another word you&#39;ll see for them each one is a finicula it&#39;s a fun word right f n so you&#39;ll see either the ventral column or the vental finicula you&#39;ll see the lateral column or the lateral finicula and you&#39;ll see the posterior or the dorsal column or finicula running up and down through that spinal cord are clusters of axons there&#39;s a new term here I need you to know though and that is that within the spinal cord there are no nerves instead inside the spinal cord we have what is referred to as tracks it&#39;s just a it&#39;s a nomenclature type thing so in the peripheral nervous system a group of neurons axons I should say a group of axons is called a nerve in the central nervous system a group of axons is referred to as a tract and so what we see see is that going up and down the spinal cord there are ascending tracks and descending tracks ascending tracks are the tracks the axons carrying information from the periphery and going up the spinal cord toward the brain so those are the ascending tracks and also in your spinal cord are descending tracks these are carrying motor information down which will then go out of the spinal cord and go to your muscles or to your glands the spinal cord is the main connector between your body and the Brain but there&#39;s one job that the spinal cord does all by itself that does not include the brain and that is the spinal cords responsible for your reflexes reflexes you know what they are they&#39;re they&#39;re really quick automatic involuntary reactions we usually think of them as reactions of muscles we&#39;ve all watched Law and Order type shows a person is hooked up to a lot a lie detector test and uh maybe you&#39;re not aware of this but there&#39;s a lot of components to that lie detector test the examiner is asking questions and the person being asked the questions they&#39;re looking at his or her eyes looking for changes in the pupil diameter they have a monitor on their skin looking for changes in sweat they have a monitor on their heart rate seeing if their heart rate goes up or their breathing rate goes up all of those things typically will be increased if you&#39;re lying right your your heart rate goes up your breathing rate goes up you sweat a little bit more your pupils change and so these are all reflexive responses U as an example another example that you&#39;re probably very familiar with is touching a stove or stubbing your toe so let&#39;s talk about touching the stove uh you touch stove even before you are consciously aware that you are burning yourself you will quote reflexively pull back from that hot surface you&#39;ll pull back before you&#39;re even aware of it right you pull back and then you go oh man that hurts right you you pull back before you even aware of it consciously how did that happen there&#39;s this is the wiring What&#39;s called the reflex arc of the of the reflex so something in this case a pin poked your skin now you&#39;ve got nerve endings in your skin uh they picked up on that pain sensation those signals traveled through that nerve entered into your spinal cord notice um as information comes into the spinal cord always goes in the posterior roote or the dorsal root and that that neuron is now going to speak with some interneuron found in the spinal cord these interneurons are going to make the decision hey that that&#39;s not good and they&#39;re going to send information out through a motor neuron always out the anterior route and in this case going to a muscle so if you were reaching out touching the stove perhaps that reflex is telling your biceps brachii or your brachialis to flex your elbow away from that painful sensation again none of this includes the brain this is happening before that now right after you pull away your brain does become aware of it and you become aware that you have burned yourself and all of that that goes on but the immediate response of a reflex here are the five steps and it does not involve your brain let&#39;s look at another reflex this is so cool you&#39;re you&#39;re walking along and with your right foot your Barefoot it&#39;s somewhere it look like and you step on something sharp so those pain receptors in your right foot are going to send that signal up to your spinal cord notice it comes in the back door and goes in it&#39;s going to speak to those interneurons and then those in neurons are going to say hey dummy you just hurt yourself go out the front side go back down this motor neuron is now going to go down to H I wonder what muscle would cause you to flex the knee that might be the hamstring group right and maybe your soaz major was involved in retracting that leg up and you would do that but what&#39;s so cool not only did you lift up your right leg but other interneurons in your spinal cord went to the other side of the spinal cord a contralateral relationship spoke to other motor neurons that now went down to your left leg and told your left leg to extend so that would be for example your quadriceps muscles right would be involved in um causing your leg to extend at the knee so this is a more involved reflex but still all of that would happen even before you were consciously aware you would withdraw the the foot from the pain and simultaneously you would extend the other foot so that you don&#39;t fall over very cool stuff and because there&#39;s quite a few synapses Happening Here in the spinal cord this is referred to as a poly synaptic reflex so just looking a little more carefully at the spinal cord again now you see the nerves are numbered C1 through C8 T1 through T12 the lumbar and the sacral nerves and then this particular image also has the plexuses labeled so the cervical plexus the brachial plexus going off to the arm the lumbar plexus and the sacr plexus note the sacr plexus is heading behind going down through that sciatic Notch and heading down the posterior thigh whereas it&#39;s hard to see here I know but those lumbar nerves are traveling down the anterior side of the pelvis are traveling down the anterior thigh as you look at the cadaveric image here you appreciate that the spinal cord you can see those um the the nerve Roots merging to make the root and you&#39;ll be seeing more of these images you&#39;re going to be learning the names of quite a few nerves now the great thing about naming nerves is that you already know most of these terms these terms the these the nerves are named either for the region of the body through which they pass or they&#39;re named for the muscle or the region that they go to so the naming of or the bone along which they travel so the naming of nerves should not be a challenge for you you&#39;ll have to take out your book make some notes but I think you&#39;ll find this to be pretty straightforward so for example the the nerves that go over to the arm uh the brachial plexus there are five nerves that run down the arm uh there&#39;s the axillary nerve H makes sense it&#39;s up in the armpit area there&#39;s the radial nerve we&#39;re going to see that it comes down and runs along the radius makes sense the owner nerve comes down runs along the pinky side again runs along the Ona that makes sense there&#39;s a nerve that goes right down the middle of all that and that is the median nerve okay right down the middle and then finally there&#39;s a nerve referred to as the muscular cutaneous which is not shown on this image now there are 20 some muscle nerve combos that you&#39;re going to be learning for example there&#39;s a separate handout for this but you&#39;re going to learn that the deltoid muscle is controlled by the axillary nerve now folks this is not that hard you&#39;ve got to do some you have to do some matching up but if the deltoid muscle is sitting in the shoulder area as you know and the axillary nerve is sitting here in this area I would argue that that is not a huge stretch right for you to learn that the deltoid muscle right that would be sitting here is controlled by this axillary nerve likewise um the radial nerve right the radial nerve comes down and it goes right here right and this it&#39;s going to control your triceps brachi the muscle that&#39;s or the uh nerve that&#39;s not shown here the muscular cutaneous is going to be controlling your biceps bracha so look at that handout I think there&#39;s 26 or 27 of those nerve muscle combinations that you&#39;ll need to learn so while we&#39;re not directly testing on the muscles and Bones from the first lab exam you can&#39;t forget it you&#39;ll be applying that information as we move forward let&#39;s take a look at the brain the brain is the most complex of the organs that we have studied so far you&#39;re going to learn quite a bit about the brain um this slide is showing you what&#39;s called the functional areas of the brain that is each lobe of the brain has a number of jobs that it is primarily responsible for there are certain regions of the brain when damaged uh the person can no longer do certain things so if you were to lose a significant portion of your frontal lobe due to a stroke or to some sort of brain injury you would have def deficiencies in your thinking your memory your behavior and it&#39;s your frontal lobe that initiates your movement So when you say or when you when your brain tells your biceps brachi to move those instructions are coming from a portion of the frontal Lo If instead you had damage to your Pari title lobe loes left and right then you would probably have some issues with language and you would also have issues with touch and other sensory type of information if you had damage to your ocial lobe that would affect your site perhaps if you had damage to your temporal lobe you could have significant issues your hearing uh also some learning some feelings as well there&#39;s a lobe that&#39;s not shown here but if you were to crack open this brain along this s Fus this fissure here and look inside there&#39;s another lobe called the insula that&#39;s where your taste centers are if you were to have brain damage to your brain stem this purpley area then you would have issues with your ability to breathe or regulate your heart rate or regulate your body temperature and if instead you had issues or damage to your cerebellum you would probably have issues with your balance and coordination now there&#39;s a whole lot more that the brain does but these are the main areas uh the main jobs if you will of these regions of the brain as you look at the brain uh in a mid sagittal cut like this uh there is a number of structures that you you&#39;ll be looking at you will be naming the lobes right the frontal lobe parial lobe you&#39;ll be looking at the ocial lobe temporal lobe would be on the farest side right here when you open it up midsagittally there&#39;s a very thick band of white matter here that is the Corpus colossum there&#39;s another thick band of white matter on the bottom side that&#39;s referred to as the fornex there is an area here I&#39;m circling this area is the thalamus right below that is is the hypothalamus so we have the hypothalamus right below the thalamus there&#39;s a large oval region in the brain stem referred to as the ponds there&#39;s also an oblong region called the medulla oinga through here and then if you imagine here&#39;s the oipal bone coming around the base of the skull everything that passes through that foran Magnum would be spinal cord there&#39;s a few more structures on here that you&#39;ll be learning but those are some of the big ones for now in addition to learning a number of the the nerves that come off the spinal cord the spinal nerves there are also 12 pairs of nerves that come off the brain and the brain stem referred to as the cranial nerves these nerves are different in that they are numbered uh when they&#39;re when uh they&#39;re either named with a name or they are numbered always using Roman numerals and you&#39;ll see those Roman numerals here 1 through 12 so if you don&#39;t know your Roman numerals it&#39;s time to learn them and specifically in this lab you will be seeing the optic nerve coming off the eye in your dissection and you&#39;re going to see the vestibular clear nerve in the ear as you learn about the ear now you are not responsible for identifying these nerves on the brain so if you flip over a brain model or look at your Atlas and your book you&#39;re going to see these cranial nerves labeled you are not responsible for identifying the cranial nerves but you do need to learn uh the cranial nerves what they do okay and in some of these cases some of these cranial nerves also control muscles so for example the accessory nerve the 11th cranial nerve you&#39;re going to learn controls your trapezius and your sternal Clomid muscles think about your shoulder muscles the ability to shrug and turn your head is controlled by one of these pairs of cranial nerves the accessory nerve or cranial nerve 11 you&#39;ll also be learning that a number of muscles in your face for example the zygomaticus the orbicularis oculi the orbicularis orus are controlled by the facial nerve and you&#39;ll be learning that the muscles that move the eye are controlled by the ocular motor the trolear and the abducent nerve so that information is coming and you&#39;ll be learning more about that in this unit as well as in lecture two more structures to be looking at today structures of the eye and then in the next Slide the structures of the ear let me just you&#39;ll also be dissecting an eye today just looking at this quickly and then you&#39;ll be digging in a little bit deeper but there are three main layers of the eye the white of the eye is called the Scara now vocabulary will&#39;ll learn later that scare means hard as you are cutting through this outer layer you will experience just how tough and hard that outer layer is not hard like a rock but very very tough the middle layer is referred to as the choid the inner layer is the retina retina retina you know reticulum you&#39;ve seen the endoplasmic reticulum uh you know that retina or reticulum means a network reticular fibers and so the retina is a network of receptors that receive visual signals right visual receptors in the eye the optic nerve there it is that is cranial nerve number two that&#39;s coming off the posterior eye it&#39;s going to carry that visual information from the retina to the oipal lobe of your brain as well as other parts of your brain we see some of these muscles of the eye coming around you will be learning and did already learn the muscles around the eye this would be the superior rectus and this would be the inferior rectus muscle around the eye the lens of the eye is shown here in your body in a freshly killed specimen it would be a clear uh very Crystal Clear structure in your dissected eye it&#39;s going to be much more cloudy kind of yellow ysh in color simply because it has been sitting in the solution the outer layer covering where the light goes in is called a cornea you may have scratched your cornea before you know that that&#39;s a very very highly innervated very painful scratch to scratch the cornea in the front of the eye there&#39;s a space an area referred to as the anterior cavity and in that anterior cavity there&#39;s a liquid called aquous humor in the back of the eye in the posterior cavity there&#39;s a jellylike substance called the vitus humor so in lecture we&#39;ll talk about how this all works together but your job now is to learn the structures of the eye and then finally the ear again focusing on the structures not the physiology not how this works but the ear is broken up into three areas there&#39;s the outer ear there&#39;s the middle ear and there&#39;s the inner ear the outer ear is composed of the Pina you may also see this called The Oracle that&#39;s the Flappy part of your ear and uh I guess we&#39;ll talk about a little bit about how the ear works so the sound comes in through your Canal ear canal and hits this membrane okay you know it as your as your eard drum but we&#39;re not going to give credit for that we&#39;re going to call it the tanic membrane like the tempany and the orchestra the big drum so that tanic membrane is going to vibrate uh that vibration is now going to be transferring that Vib vibrational energy to three bones there&#39;s three three bones collectively are called the oces the first one is the malas then the incus then the stapes you&#39;ll also hear stapes so stapes or stapes these now are the last bones that you need to learn so in the skeletal unit we learned 200 bones of the 206 bones there are three of these oses in each ear so now you know all 206 bones in your body that vibrational energy is going to go on this stapes and there&#39;s an opening behind the stapes and that energy is now going to come into the entryway here this entryway is called the vestibule the vestibule you may know that vestibule just means an opening into something uh architectur talk Arch Architects talk about a vestibule in a building or in a church in your body you have a nasal vestibule an oral vestibule uh there&#39;s a vaginal vestibule and as you come into the opening of the inner ear you look off to one side you see three semicircular canals these three semicircular canals are involved with balance to the other side you now see this spiral structure called the Clea and that&#39;s where your hearing is occurring we&#39;ll deal with more details later uh the information for the semicircular canals travels through a portion of a nerve called the vestibular nerve the information for for hearing travels through the clear nerve these two nerves come together so these two nerves come together to form one nerve and that is the vestibular clear nerve and it is also your cranial nerve 8 okay so you&#39;ll see it called either the vestibular clear nerve or vestibular or or the cranial nerve number eight so at the end of this lab you&#39;re going to be doing a couple dissections each of you has a sheep brain the Sheep brain is going to have hopefully the outer layer on here that&#39;s the dura moer here is some spinal cord keep in mind that in a four-legged animal uh their their architecture is a little bit different so um in our in our brain the cerebellum uh would be sort of down below the um the loes but on a sheep the cerebellum is here right and the ocial Lo would be U would be deep to that you&#39;re also going to be having an eye and you&#39;ll be cutting the eye you&#39;ll be doing some labeling some activities you have a choice you can either after you&#39;ve done your dissections lay out your pieces on a piece of paper write the structure and draw a line to it the best you can or you can take a video of pointing to each of the structures on the dissection rubric list and upload that so you&#39;ll be either uploading images labeled images or uploading a video to your instructor at the end of this lab

Transcript for:Lab 6: The Nervous System

Transcript for:
Lab 6: The Nervous System