Integrative Biology 131 – Lecture 26: Peripheral Nerves



good morning now there lovely morning isn't it and it's lovely down at UCLA too just to know that we also they also have nice weather can anybody hear me back there no I can tell by the looks on their face as they can can you please adjust the mic somehow I'll keep talking till it goes up is that right is it coming through yet can you hear me in back no there's still no response can you hear me now yes thank you yet to me that's my friend back there he usually sits up here so he talks to me now he's way back there thank you let's see we have a Jacqueline de Sola Aires is Jacqueline here no Jacqueline sometimes they come in late and come up afterwards so we have to take three instead of two hmm let's see then is Carolyn win here Cara there's Carolyn all right perfect we'll see you after class Carolyn and then we have Kenneth Ruth is Kenneth here there's Ken fine well you'll meet Carolyn who's just right behind you there so come up after class please let's continue now with our cranial nerves first we'll do a little review because we've given them to you several times from different directions but just to bring them together now so cranial nerves you recall we had a forebrain we had a midbrain and a hindbrain which cranial nerves were dealing with the forebrain what's the very first one one and two how about the midbrain cranial nerves are functioning with the midbrain you can guess at least 1 3 & 4 3 & 4 are both midbrain so look at then hind brain will have 5 6 7 8 9 10 11 and 12 so you can see when you get an injury and one of these special divisions what happens when you injure here and how many of your cranial nerves can be affected and clinically this is one of the most important things I can tell you to know where your cranial nerves are coming from so if you see a peripheral expression of a cranial nerve you know what part of the brain is having problems it's the quickest put way alright so this gives you just the idea of how these are divided and now what we want to do is just go through them and give their names and brief functions for each so we have these are specific nerves and we said one was olfaction the olfactory nerve and obviously it helps us smell but I was just thinking about its derivative if we are adding on our spinal cord with evolution and one is coming from the most recent part of the brain and yet you think that olfaction is so important for survival and for sex I mean it's way up there the last to develop so the optic nerve is two optic obviously for vision and three what's three ocular motor ocular motor what does it do ocular eye mover so it will go to four of the six extra ocular I muscles four of six extra popular eye muscles so to give you those briefly here's our eye pupil we'll have a superior rectus up here rectus was straight you remember from your rectus abdominus this is superior rectus and we have an inferior rectus just to make this easy for you we have a medial rectus medial rectus and we have an inferior oblique so it's going to be going in this direction inferior oblique so this gives us our four one two three four extra ocular muscles that are all supplied by three so let's go on to four four is trochlear what this trophy or mean right no good guess but wrong Puli Puli because when you see the trochlear it looks like a little pulley to rotate the superior oblique so this until you see it it doesn't make much difference but once you see it you'll never forget it so this is two one extra ocular eye muscle and it will be the superior oblique so it's up here superior oblique so we'll put it here it's well just repeat repeat repeat alright so we've got five of our extra ocular eye muscles let's go to our fifth cranial nerve what's it called trigeminal it's got three parts trigeminal so we're going to have a motive component motor five does anybody know where motor 5 goes to muscles of mastication get lockjaw if you disturb this muscles of mastication what are your muscles of mastication Brendan Julian that's what it means but what are the muscles that are holding you to that's ok masseter and temporalis sure you've had them so now sensory this will be sensory to the face and sensory to the nasal and what are the cavity oral cavity so sensory to the face we'll just do it quickly just whoops not that quickly so if we take this part this part it's trigeminal this will be the opthalmic division this will be the maxillary division so that's easy just upper jaw face over upper jaw and the mandibular division just to give you the origin of the term with its three sensory components for the face let's look at 6 6 is abducens what does AB mean away away so what muscle is missing on our eyeball the lateral rectus right so abducens will be the lateral rectus I muscle and we can put it in our drawing it's going to be over here this is lateral rectus it's easy rectus so what happens if we cut the sixth cranial nerve how can you tell when the person comes into your office if they have a sixth nerve defect no just the opposite you don't have lateral to pull it sideways therefore a medial is pulling so you have what's called medial strabismus can anyone just have one I do strabismus strabismus you know it's cross-eyed I can do both together but I can't do I freeze get a student everybody comes to looks because they can bring that one eye over but nobody in this class know maybe you haven't tried but anyhow so injury here just to give you the dynamics of knowing cranial nerves will be medial strabismus medial cross side medial strabismus okay anyhow you're wise enough to know what it means but cross-eyed straw business let's see we want media deviation I all right this brings us in to seven what is seven facial and we've learned about facial when we had which muscle how did I tell you to tell somebody immediately when they come in the office whether their facial nerve is functioning I'm sorry pardon yes front Alice sure tell them to wrinkle the forehead raise the eyebrows right when you see somebody in the morning you can't speak you just do that they know you're saying hello right all right so that's facial so we have a motor component muscles of facial expression review review review we have a sensory component how many enjoyed that being into contact this morning for breakfast taste buds to the anterior two-thirds of your tongue so the sensory component of facial tastebuds anterior two-thirds of tongue when you get your neurology exam you'll put some different flavors on your tongue and see if you can taste them and you know whether your sensory is fine for the seventh let's see then we have salivary glands the submandibular submandibular and sub maxillary you know exactly where they are because of their names salivary glands then we have eight what is eight pardon I hope yours is working now that's only half of it what's the other half this fibula cochlear nerve vestibular part for balance cochlear part for hearing pure sensory nerve like the visual system but this is so complex we think visions complex then it gets us up to nine what's nine glossopharyngeal so it tells you where it is what's blossom tongue for injeel you know now now you know your pharynx so this will be going to muscles of pharynx and larynx other muscles are going there too but we're just doing a brief introduction so how are you going to test this one just tell them to swallow you feel your time going back right over your oral pharynx right you should be able to now write test swallow what's and as you get your friends and you go through all of these and test everybody's cranial nerves ten everybody know it's the vagus by now we've mentioned it so many times the vagus wander so it will go to this aura in thoracic and abdominal cavity we took it to the heart what was it doing for the heart parasympathetic what does parasympathetic do to the heart slows it down so now we're past it up to 1111 it's a spinal accessory spinal spinal accessory what Laurel does that mean for anybody who's interested in evolution would be fun to try to figure out why it has a spinal component to a cranial nerve it's got to come from the cervical cord come up in through the foramen magnum and join the cranial component so the spinal come opponent is coming from upper cervical segments of cord and it joins then with medulla components and we'll go to muscles in the neck what's a major muscle in the anterior neck that you've learned sort of started sternal start a fight a mastoid sternocleidomastoid and what's a major muscle at the posterior aspect of the neck trapezius so here's a cranial nerve it's a funny nerve coming back down why didn't it just go out to the neck to begin with why didn't things just go to the neck who knows twelve what's twelve hypoglossal everybody knows that I hope so and the hypoglossal is going where tounge tell somebody to stick out the tongue and if they stick it out and it goes you know that they have disturbed the hypoglossal nerve on the left side there's no muscle there innervated to get it straight so you tell them to stick out the top it deviates it deviates to the injured side so this goes to come muscles and injury deviates to injured side did I ever tell you the story about the little girl in Australia who was 12 years of age and what's autistic never communicated with anybody did I tell you that little story no very quickly then because somebody knew her cranial nerves a nurse did and there were a meeting and this little girl was there and nobody had talked to her she hadn't talked to her back again and the nurse said if you hear me stick out your tongue she knew her cranial nerves she went down the spinal cord I did it down the brainstem as far as she could with a cranial nerve and the little girl stuck out her tongue that just opened the whole thing about ten years later they wrote a book together so no your cranial nerves very simple simple and important okay with that let's go to our spinal cord and don't sell your spinal cord it's so important many people want to be neurosurgeons because they think they're going to be brain surgeons but very little brain surgery actually takes place in case of tumors or accidents spinal cord injuries are common that will be the bread and butter of this is what the neurosurgeons tell me of tomorrow its operating on the spinal cord so the spinal cord is found in the vertebral canal with its meninges its coverings those are the CT coverings in the embryo the cord fills the entire length of the canal entire length of canal at birth how much does your cord fill and I always ask that because I've seen it on medical boards how far does the cord go at birth you think this these are trivial almost every statement has meaning somewhere right so that birth cord to l3 in your body's adults where does the cord go between l1 and l2 there's a differential growth between the vertebra and the court and this is why you keep getting this cord going up as the vertebra are growing rapidly so in the adult it goes to l1 l2 so now let's introduce the term cauda equina horse's tail did you know you had a horse's tail but it's made up of nerve roots harder that's tail equina for us and it's made up of nerve roots why does it exist if I have my cord and I have my segment cervical thoracic lumbar sacral and coccygeal how many cervical nerves eight how many thoracic 12 how many lumbar five how many sacral five okay how many cranial nerves total how many thirty-one what pairs so how many ajjil just checking you alright one coccygeal gives us 31 pairs now we have a vertebral column I'm just giving representative samples here to get the idea across of what causes our cauda equina and these represent vertebra these little boxes because I've got to get my spinal nerves to go out so forth so when I'm at the cervical and thoracic level my nerves can come out and just go out like this through these but as I get down further these will go down and then to get to these these will go down and these will go down and so forth and by the time you do this bilaterally you can see where this horse's tail has come in to this area where this is at l1 l2 where the cord has stopped but the nerves in order to go out through the intervertebral foramen these are nerves and enter vertebral foramen they form what's called the cauda equina so that looked like a tail to you I'll show a picture and you'll agree that it does cauda equina so that gives some basics about the court let's look at the protective coverings of the cord because they play a very important role we saw some of them and what they do in the brain when you got your dura mater forming sinuses you saw how it became modified in the skull let's look at the meninges in on the cord let's do the cord and very simple again because we won't be following them out on the nerves we'll just be getting the basics so here's our conus medullaris which is the end of the cord conus medullaris what level is it you know why now – right that's where it's ending no one L – you'll see why that's very important to know you can count up from your sacral lumbar joint four five and then you get where l1 is so you know where your cord ends but now we want to put on our three layers we are going to have Pia mater a rat guide for spider and dura mater what did we say PIA mater meant gentle mother what did we say dura mater meant harsh mother so let's put Pia in yellow Pia is adhere it to the exterior of the CNS whether it's brain or spinal cord it is protecting we said it formed appeal glial membrane if you remember to protect when you get something sharp entering your nervous system so the Pia mater is inherit to spinal cord and then we have the arachnoid leave space between the pia and the arachnoid so in pink we've put in the arachnoid membrane and it has trabeculae remember trabecular you've seen those in your lymphatic organs networks of fibers connecting the arachnoid to the pia and these trabeculae that's what gives it the name spider for spiderweb for arachnoid spider what flows in the subarachnoid space that we've created between the arachnoid and the pia cerebral spinal fluid so CSF flows in sub arachnoid space that's cerebral spinal fluid do you know how much CSF you produce each day 700 cc's make the back it's all got to be reabsorbed every day is that phenomenal how active it is all right so our outer membrane now is going to be the dura mater and the dura mater is you've seen it it's heavy thick connective tissue protective membrane so in green we put in our dura mater it's thick bathing cap like thick CT membrane and what's important here is that the dura mater continues on down to sacral 2s2 and what it's formed here the cord ended up l1 we're down at s2 we have a sac it's called the dural sac and what's it filled with CSF has anybody had a spinal tap Oh heaven forbid one person two of us spinal taps so they have to count down to be sure they're lower than l1 l2 to put the needle in to draw that spinal fluid right but you see the importance of knowing that you won't hit Kurt or the cord there you'll hit the cauda equina but they usually move aside when you go in with the needle so this is a level for a spinal tap or spinal anesthesia they can put the anesthesia there for delivery for birth so that you just get the lower part not the upper part all right all of these play a role all right so that's our our meninges now let's look at a cross-section of a spinal cord I told you I had a student there's the thoracic area gets tumors more frequently then the rest of the court nobody seems to know why she had a tumor in her thoracic court we followed her she kept having it removed it kept coming back she eventually died but she sure was a good example to let you know that some parts of the cord form tumors more frequently than others why lots to learn so we want cross-section of cord oh let's take our old familiar part first so you can see where the cord Stegman's are derived let's take an embryonic section and I'm sure you remember this right we'll do it like this what do we call the center of our chord here what is it gracious what's the first part go to be pardon central canal sure thank you does anybody remember what the central canal is lined with you're gonna get all of this because you can get tumors of these cells so in green we have our upend Emma lining central canal can you see your spinal cord back there you ever tried to imagine it ever thought of your durossac we call what I've put in red here the mantle layer and the mantle layer consists whoops primarily of nerve cell bodies so we call it what gray or white matter grey matter sure and it's surrounded then by the marginal layer which is marginal layer which will be fibers then nerve fibers and they're myelinated so what do we call this white matter fat is white right so these are myelinated fibers we'll show pictures of demyelinating diseases taking away your white matter so now that soy we see it in the embryo but you've been told that you lose about 50 percent of your neurons before you're ever born during embryogenesis many more neurons are formed than you'll ever need they're precious they're over produced so if we look at it cross-section of the adult cord you think you'd like to find out how to hang on to all of those neurons so you don't lose them you want all those he you want choice ones so let's put in now our adult cord which we're we're going to change our configuration completely and now what do we have we have our our central canal is reduced to a very minor structure but it's still present there's some diseases in fact only the tissue around the central canal so you need to know it central canal then we have our mantle layer has been changed into what we call horns as we see them in a single cross-section so you see how many nerve cells have been lost in the spinal cord because originally this was all a circle but that area which becomes functional stays so this is going to be our posterior horn and this will be our anterior horn sound familiar anterior horn cell what did we say about anterior horn cells they're the largest right 135 and we said we'd see them eventually these are your big motor cells that are firing for me to write on the blackboard but now we look at our marginal layer out here all our white matter and that will be a white matter so we see the gray matter has a specific form so does the white matter but now how are we going to make this functional is our posterior horn going to be sensory or motor sensory good for you right as we showed it very early but if we took this across here this was century and this was motor right your Aylor and basal plates so this will be sensory now and our anterior horn will be motor we told you the polio virus attacks these anterior horn cells get paralyzed with polio all right now what we want to do is see how the input comes it makes use of this sensory and we'll make a simple sketch then cross section of our cord again with our horns and this time we're going to introduce our dorsal root ganglia familiar friend dorsal root ganglia group of nerve cell bodies outside the CNS over there chain of ganglia alongside the cord so now we want to bring an impulse into the cord let's just take a reflex it's not going to go to the brain it's just gonna go in and out so let's have a pin out here it's going to prick your finger hit hurt pain you have you are silly sometimes but oh there goes our time I do want to take this in so the pain is gonna go to paints usually travels much slower than this but we'll take it in just because we've got it set up here what kind of nerve cell do we have an ad or sarit ganglia what kind of nerve cell is that pseudo unipolar good I told you I heard a PhD exam and the kid didn't know it and play he got in trouble it seems trivial to you but when you work in the field different viruses will affect this cell that won't affect this one so you learn them you're just getting your introduction so here my pain is coming in and it will go over what's called the dorsal root here between the ganglion I see you can go in and cut the dorsal root so that you don't get pain when you get terminal cancer and it hurts too much so you need to know these things and then we have an interneuron when we say about entering neurons what are our three types of neurons motor sensory and inter neurons inter neurons they connect the two most of the nerve cells in your central nervous system are inter neurons connecting what's coming in and out and now we have our anterior horn cell and it's going to come out and it's motor so it's gonna come out to some skeletal better motor skeletal muscle fiber and you'll have an action and this is your ventral root don't ever let show slides but that gives us a simple pain and motor out [Applause] all right this is our familiar one here's our forebrain our midbrain and our hind brain right familiar are you with me or you're too busy packing okay we had one and two up here for brain three and four mesencephalon and all the rest from the hind brain here it shows two coming out from the forebrain to form the optic Cup which will be your retina so it's neural origin in the next one and this shows that within the brain these are what we call optic tracks but the optic nerves will be coming in from the top of your nose olfactory impulses these are your optic nerves these are your third nerves your fourth nerve comes up on the opposite side here's the fifth six is here seven and eight are here this is called the pontine cerebellar angle a frequent place for tumors and then you have nine ten eleven and twelve coming out here in the next one and this just shows the continuity of the brain you can't have a brain transplant what's going to happen when you cut off all this input from your total body you can transplant pieces but even those haven't been too successful but you could see the nerve roots coming out here and the cauda equina here in the next one this is showing the dorsal root ganglia in the inter vertebral foramen your sensory ganglia in the next one and this shows the coverings this is your heavy dura mater the arachnoid and the pia will be clear down here and this is a pea a catchment laterally in the next one and this is the real thing but again to show the cauda equina in the next one and this shows the cord but in the cord all of these are a sending fibers white fibers that have come in going up to the brain in red the descending on the opposite side so next time we're going to fill in a little bit of the cord so you can see what transpires and what can be cut and what can't be cut in case of too much pain or too much of other sensory mechanisms or firing in the next one and this shows multiple sclerosis the small area of demyelination in the posterior lateral portion of the cervical cord so here's our gray matter here's our white matter and in this lateral area it's demyelinating now these specific functions look at this this is multiple sclerosis with extensive extensive lesions occupying practically the entire cross section of the spinal cord that's something in the next one and this is just to show tumor formation we'll put in things occasionally so we'll ask you symptoms if you have a tumor here this is pons underneath it's a cerebellum you've got this big tumor growing here what might you see in the next one I think you

20 thoughts on “Integrative Biology 131 – Lecture 26: Peripheral Nerves

  1. Thank you!!! Awesome lecture. I'm glad I missed class and needed to find a lecture to watch. 🙂 Such a cute and intelligent lady and a great teacher!

  2. Best anatomy lecturer ever! LOL at 09:21 'not that quickly' haha she teaches and cracks jokes! Wish she would come to Ireland

  3. Thank you Dr. Diamond. Your lectures are very well presented and I believe helpful to many people in many different ways. I have borrowed some of your wisdom for my own classroom. On another note, with all due respect, I would humbly submit that there is a better explanation for the location of cranial nerve I than what may lie in trying to untangle some sort of evolutionary mystery of sorts. 🙂 God bless you and thanks again.

  4. Don't get me wrong, but this is spoon-feeding in our country or university, at least. Is this how teachers/professors in the US teach? My professors don't really elaborate everything to us, like the good lady in the video. I mean, they just speak a little and let us read/research the topics and voila! HARDCORE EXAMS which you can't totally finish within an hour. With vast scope in the subjects, you can't be so sure what comes out or not.

  5. I AM AWESTRUCK.
    My professor hasn't written as many words during our entire anatomy class as she has on a single board. His hectic lectures were also as coherent as… Let's just say that at one point my 5 consequential lecture notes were about epiglottis, testes, heart, kidney and nasal cavity (in that order).
    I wish I found these lectures before having been flunked 4 times – even though I know all the things mentioned, and I'm not even a med student but a biology major.
    THANK YOU, DR. DIAMOND!

  6. Wow. Cursive and roman numerals in chalk for almost an hour. That's how you know this woman has experience.

    Plus, all that there anatomy stuff 🙂

  7. A trick to remembering Cranial Nerves
    CN I – Olfacoty
    CN II – Optic
    CN III – Oculomotor
    CN IV – Trochlear
    CN V – Trigeminal
    CN VI – Abducens
    CN VII – Facial
    CN VIII – Vestibulocochlear
    CN IX – Glossopharyngeal
    CN X – Vagus
    CN XI – Accessory
    CN XII – Hypoglossal
    Take the first letter of every cranial nerve and you have 'Ooo Ooo Ooo To Touch And Feel Very Green Vegetables AH!'

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