[Music] all right you guys welcome back to another video lesson from ICU advantage and in this lesson I'm gonna take you through the basics of these cranial nerves and really help you to understand what the cranial nerves are as well as a few different ways to help you guys remember which nerve is which before we begin though my name is Eddie Watson and this is ICU advantage my goal here with ICU advantage is to take these complex critical care topics and really try to break them down and make them easy to understand for you guys I hope that I'm able to do just that and perhaps by the end of this lesson all of our into subscription from you if you do make sure you hit that Bell icon and select all notifications that way you'll never miss out on a lesson alright so let's go ahead and get in here and start to talk about what are our cranial nerves and so essentially what cranial nerves are our nerves that originate directly from either the brain or the brainstem and when it comes to these cranial nerves there's actually 12 different cranial nerves that we have and each one of these cranial nerves is going to be paired and present on both sides of the body now we use Roman numerals to number these and we basically number them based on where they emerge from the brain and the brain stem when looking at it front to back so in order to view these cranial nerves we want to be viewing the inferior surface of the brain which is what we have going on here and essentially what these cranial nerves are doing is that they are relaying information to and from various parts of the body which are primarily gonna be in the head in the neck and then having that communication with the brain now in order for this relay of information that take place we have two different types of neurons that we're gonna see with these cranial nerves and these are neurons that we call a ferrant and efferent now the afferent neurons are sensory neurons that are carrying signals from various sensory stimuli back towards the brain now our offender our motor neurons that are going to be carrying signals away from the brain to either have some effect on muscle or some other target cells and you'll see here in a minute when we go through and talk about these different cranial nerves but some of these cranial nerves are gonna be a ferrant some of them are gonna be efferent and some of them are actually gonna be a combination of both all right and so with that said let's actually move on and talk about the different cranial nerves now what I've done here is I've gone through and colored each of the 12 cranial nerves so that they'll be easier to identify as I'm talking about them here and so what I'm gonna do is I'm gonna go through and as we talk about each of these cranial nerves I'm actually gonna use the same color that I have identified on the cranial nerves themselves to help to identify where it is that we're actually talking about all right so the first nerve that we're gonna begin with is as you configure cranial nerve one and this is going to be our olfactory nerve and this cranial nerve is essentially this one that you see right here in green now this cranial nerve is also the the first of only two nerves that actually originate from our cerebrum and this one is essentially a sensory neuron that is responsible for something that we call olfaction or what we commonly know as sense of smell all right the next cranial nerve that we're going to talk about is this one here in blue and this is going to be cranial nerve two which is our optic nerve and it's this nerve that is the other one of the two nerves that are the only ones originating from our cerebrum and just like the olfactory nerve the cranial nerve to the optic nerve is solely a sensory nerve and is going to be the one that is responsible for vision all right so the next three cranial nerves that I'm going to talk about really can be thought of as a group because they all essentially have a similar effect and these three cranial nerves that I'm going to talk about are cranial nerve three right here cranial nerve four right here and I'm actually going to skip to cranial nerve six right here alright so the first one that I pointed out here in the lighter orange this one is cranial nerve three and this is our ocular motor and this particular nerve originates in the midbrain and this one is actually strictly a motor neuron and this nerve here actually has a few different functions one is it plays a primary role in eye movement but it also plays a role in some autonomic function such as our eyelid elevation our pupillary constriction as well as the reshaping of the eye and the lens itself something we call lens accomodation now after cranial nerve 3 comes cranial nerve for something that we call our trochlear this one also originates in the midbrain and this one is also a motor neuron and plays a key role in our eye movement and then we actually skipped past cranial nerve 5 in order to talk about cranial nerve 6 which is the one in dark orange and this is one that we call the abducens this one actually originates in our ponta medullary region but just like the last two this one is also strictly a motor neuron and if you haven't figured it out this one actually once again plays a very important role in eye movement now for these three cranial nerves I really didn't go into depth in talking about the the different types of eye movements that they're responsible for in fact I am gonna save that for a future lesson where I'm gonna go more and depth into each one of these cranial nerves but just as a little bit of a hint here for cranial nerve 6 this is the one that we call abducens this is because this one actually is in charge of the abduction which is moving lateral into the outside of our eye so that's kind of where this name comes from alright so let's talk about cranial nerve number 5 which is the one that I skipped past and is right here and cranial nerve 5 is one that we called the trigeminal now the trigeminal actually originates from the pons and this is going to be the first of the cranial nerves that has both the sensory and the motor neuron so it's both a ferrant and efferent now for the sensory portion of this nerve it actually primarily is dealing with two things the first is our facial sensation and this nerve is actually divided up into three parts this is where the named trigeminal comes from but it also deals with sensation for our tongue and this is going to be the anterior 2/3 to the tongue now when it comes to the motor portion of this neuron this is where we're going to be dealing with something called mastication which is essentially the muscles involved in biting and chewing all right so let's move on and talk about our next nerve which is going to be this one right here this one is going to be cranial nerve seven which is our facial this one originates from the ponta medullary region as well and this nerve also serves two functions and serves as both a sensory and a motor neuron for the a Ference sensory part of this nerve that this is where we're actually dealing with taste on our tongue so this is going to be taste on the anterior two-thirds of our tongue but this is not to be confused with sensation that we just talked about with the trigeminal sensory nerve now when it comes to the motor function of this nerve there's a couple different things that we deal with one is it has a primary responsibility in our facial expression also our eyelid closing and it also plays a role in our salivation and lacrimation so basically our ability to make saliva and tear secretion all right moving on is gonna be our next neuron which is going to be this one right here and this one is actually going to be cranial nerve eight something that we call the vestibulocochlear this one once again originates from that Ponto medullary region now this nerve here is going to be primarily an afferent sensory neuron and this one plays an important role in our balance and our hearing and so this is where we get the name from the balance is the connection to the vestibule and the hearing is the connection to the cochlea and so hence this is where the name vestibulocochlear comes from now you may also though here this one referred to as the auditory nerve so it is important to know that you may hear this one as well all right so the next nerve that we're going to talk about is going to be this one right here and this one is going to be cranial nerve number nine which is our glosso pharyngeal now this nerve actually originates from our medulla oblongata now for this one you might be able to figure out the areas that it is impacting so it's gotten the name here glosso which we know means tongue and also has fairing which is coming from pharynx which we know would be our throat so this particular nerve is actually both once again a sensory and a motor neuron now for the sensory portion here again we're dealing with taste but now we're talking about the posterior one-third of the tongue we're also dealing with the sensation of that portion of the tongue the sensation of the pharynx and then we also get input from our sinus and our carotid chemo and baroreceptors and this is partially shared with cranial nerve 10 that we'll talk about in a minute now the motor function of this nerve is and muscles dealing with swallowing and it also aids in our salivation all right so moving on to our next cranial nerve this is going to be this one right here and this is going to be cranial nerve 10 which is what we refer to as the vagus nerve this one also originates from our medulla oblongata so the vagus nerve is actually longer than any of the other nerves that we have it's absolutely massive the name really comes from the term vagrant which comes from the wandering of this nerve it really kind of wanders all over the place as you'll see here now the vagus nerve consists of both our sensory and motor neurons and so when it comes to the sensory portion here we're dealing with sensations coming from the skin around the ear it also deals with sensations coming from the pharynx larynx thorax and abdomen and this is going to be coming from the body's visceral tissues and then it's also involved in the taste and sensation of the epiglottis now for its motor functions it plays a role in swallowing speech and coughing now it also has an efferent effect as a part of our autonomic function in particular the parasympathetic nervous system and this is the one that we can think of as that rest and digest so here it's going to have an effect of decreased heart rate increased GI motility and sweating all right the next nerve that I'm going to talk about is this one right here and this is going to be cranial nerve 11 something that we call the accessory nerve now this one also originates from the oblongata as well as the cervical spinal cord and so as a result sometimes you'll actually also hear this one referred to as the spinal accessory nerve now this nerve is strictly a motor neuron and this one plays a role in shrugging our shoulders and our head turning alright and the last cranial nerve that we're going to talk about is going to be this one located right here this is cranial nerve 12 and something that we call the hypoglossal once again this nerve originates in the medulla oblongata now this one you may also be able to figure out what its purpose is based on its name once again we see that glosso which we know was dealing with the tongue hypo we know means under so we're dealing with here a motor function dealing with the muscles under the tongue which are responsible for tongue movement all right so we covered a lot with these cranial nerves let's go over a couple different strategies and ways to help you kind of remember what these nerves are and what their function is alright the first of these ways to kind of help you guys to remember these different cranial nerves is a silly little picture that we can draw and the way it works is we start out by drawing the number one now we're going to be drawing a face here so the 1 is gonna represent the nose which we know is our olfactory then we're gonna go ahead and draw two eyes because we know cranial nerve number two is our optic nerve then we're gonna do two threes like this some fours and some sixes and these are to help us remember that cranial nerve three the oculomotor cranial nerve for the trochlear and cranial nerve six a abducens are all having to deal with eye movement then we have cranial nerve 5 which is the trigeminal which we know has to deal with our facial sensations now since we're talking about the face let's not forget about cranial nerve number 7 our facial nerve cranial nerve 8 which is our vestibular cochlear we know would make great ears right here and number 9 the gloss of pharyngeal has an important role in our tongue and our pharynx and so that makes an excellent addition right here we can add the vagus nerve as it plays an important role in that swallowing and speech and while we're here let's not forget about number 12 which deals with the movement of the tongue and then finally we're just left with cranial nerve 11 which we know is dealing with the shoulder shrugging and the head turning so as you can see a silly little face that we draw here that really kind of helps us to remember which cranial nerves are dealing with what part now in addition to this we also have a couple mnemonics that can help us remember these names now there's two different ones that I'm going to show you one is a little bit older more classic version and one is a little bit more up-to-date one so for the first mnemonic which is our classic one it goes something like this on old Olympus's towering top a finn and german viewed some hops now here I'm not sure why a finn and a german want to fuse some hops but this saying really goes back a while and helps us to remember the name of each of the cranial nerves starting from one and going all the way down to twelve the key things to know here is when we're dealing with this particular mnemonic this a here and this s here are dealing with some of the alternative names for these cranial nerves that I had talked about now each of the beginning letters and the mnemonic help us to remember the beginning letter of the name of the particular cranial nerve so here we have starting from the top going to the bottom we have the olfactory we have the optic we have the ocular motor we have the trochlear the trigeminal the abducens facial the next one is going to be the auditory which we also know is the vestibular cochlear then we have the glossopharyngeal the vagus the spinal accessory and the hypoglossal so on old Olympus towering top a fan and German viewed some hops as long as you can remember that we're dealing with the auditory and spinal accessory it can help you to remember the order of those cranial nerves now another more modern version that I actually prefer is this one here let's put it over here and this one goes on occasion our trusty truck acts funny they very good vehicle anyhow now here once again the the first letter lines up with the first letter of that particular cranial nerves name now here for this one for this cranial nerve and this cranial nerve here you can see we have different letters because we're going with the actual name that we had talked about so once again we have our olfactory or optic or ocular motor our trochlear our trigeminal the abducens facial vestibular cochlear glosso pharyngeal vagus accessory and hypoglossal nerves so hopefully one of these two mnemonics or perhaps that picture that I drew will help you to remember these the last little thing I want to do real quick here is to share another little mnemonic that we have in order to help us remember whether these are sensory or motor neurons or in fact if they're both so let me go ahead and put the letters up here and here we're dealing with s being sensory M being motor and B being both now the first one and this is actually my personal favorite go some say money matters but my brother says big brains matter more the other mnemonic that I've heard that some people also prefer is some say my mother bought my brother some bad beer my my so again really whichever these mnemonics helps you to remember this or in fact you can go online and there are other ones out there both for this and for just remembering the names of the cranial nerves some of them might not be pg-rated FYI but the important thing is that you find something that works for you in order to help you remember what these cranial nerves are and also to try to help you to remember what their functioning is whether they're sensory or motor because there's a lot of information related to these and it really just takes the time and the energy and the effort in order to burn these into your memory in order to help you know what they are without having to really think about it now like I said in this lesson this is a pretty quick overview of these different cranial nerves keep an eye out for a future lesson in which I'm going to break these down more extensively give you guys more information on these particular nerves as well as go over how we're gonna be assessing our patients for these particular cranial nerve functionings all right you guys thanks so much for watching I really hope you enjoyed this video if you did make sure and subscribe to our Channel and leave a like down below also make sure you check out another one of our awesome videos that YouTube is recommending for you right here as always thank you guys so much for watching and you guys have a wonderful day