the first set of nerves that we're going to be looking at are called your cranial nerves there are 12 cranial nerves and they're called cranial nerves because they emerge out of the cranium as you can see in the picture here in the left we have the underside of the brain cranial nerves are going to be identified by their numbers the roman numerals and they also have specific names that are associated with it they're actually identified from most anterior to most posterior so emerging out of the brain out of the brain stem especially here's your pons here's your medulla oblongata all these yellow fibers coming out of them are going to be pairs of your cranial nerves when we start looking at the roman numerals of the cranial nerves a lot of times i've noticed with the younger generation that roman numerals are no longer taught in schools but it's still used in the clinical profession and so since it's not taught in schools we're going to have to learn it now so the main things to remember when it comes to roman numerals is i v and x so i represents 1 v represents five x represents ten so i is one one and one makes two one plus one plus one that's three but remember v means five so one before five that's four one after five is six two after five is seven three after five is eight don't forget ten is x so one before ten that's nine one after ten is eleven and two after ten is twelve so we have twelve cranial nerves they're all going to be identified by the roman numerals but they also have names so one is olfactory two is optic three is oculomotor four is trochlear five is trigeminal six is abducens seven is facial eight is vestibulocochlear nine is glossopharyngeal ten is vagus eleven is accessory and 12 is hypoglossal so the challenge we're going to have in this chapter is the memorization of the roman numerals the associated names of the cranial nerves their functions as well and so because this is memory work that's going to be entailed in this portion of the chapter our book offers us some mnemonic devices which are just tools to help us remember these names so one of the mnemonic devices that our book offers us is on occasion our trusty truck acts funny very good vehicle anyhow so see how the first letter in red is associated with a very familiar word and so o for olfactory occasion o for optic t for trusty t for trochlear so this is just a tool to help us with memorizing but please be careful with your memorization look at how many things start with the letter o how many things start with letter t or what about the letter v and so you still need to know that 10 is vegas versus 8 is vestibular cochlear again this is just a tool to help us now the other tool that our textbook offers us is a way to remember the function of that particular cranial nerve in the previous video i said that whatever is labeled as s that would be purely sensory meaning one way afferent fibers going from the pns straight up into the cns sometimes they're going to be m motor so that means they're one way coming from the pns from the cns rather going out to the pns but a lot of them will be b for both both meaning mixed nerves both sensory and motor functions are going to be found here so a way to remember it is some say merry money but my brother says it's bad business to marry money and so again this is just a tool to help us remember the functions of the nerve and a tool to help us remember the names of the nerves so let's go ahead and start filling our notes down and our outlines in looking at the different cranial nerves so in this outline we see that the middle column asks whether it's sensory motor or both let's go ahead and fill that in right away because that's really really easy you just have to remember some say merry money but my brother says it's bad business to marry money so i'm gonna put my my keyboard in all caps and i'm just going to put some say mary money and trigeminal is a mixed nerve so b but abduces motor so my facial is mixed so both brother says so let me find my s on my keyboard here we go distribute cochlear that's sensory b for glossopharyngeal vagus is mixed so it's both and mary money accessory is m and hypoglossal is m so this is the some say mary money but my brother says it's bad business to marry money so we just filled in a little bit of a quick reminder of the function of the nerve whether it's purely sensory mostly motor or mixed with both sensory and motor so let's go ahead and go with these cranial nerves one at a time starting with the olfactory nerve the most anterior nerve the one that we first encounter very very close to the beginning of the brain is the olfactory this one has the ability to give you a sense of smell so sense of smell so try covering one nostril at a time if you can smell from each of those nostrils that means cranial nerve number one is working just fine so let's go to our powerpoint looking at these cranial nerves so olfactory nerves are actually quite interesting on the underside of your brain you are going to find this really big bulb coming out and this is going to be called your olfactory bulb olfaction is your sense of smell notice how you have these sensory fibers dangling down in the roof of your nasal cavity there's going to be holes in your ethmoid bone that's then going to be part of this cribriform plate and this cribriform plate that's perforated has important olfactory nerves coming up this way so if you have odorant molecules in the air outside that's then inhaled into the nasal cavity those odorant molecules will then bind these receptors these receptors will then depolarize when they depolarize they're then going to send action potential straight up through your skull into this olfactory bulb and eventually onto the brain don't forget that you have an olfactory cortex in your cerebrum and so this is purely sensory fibers that give you that sense of smell does it now make sense why when you're congested and inflamed imagine a thick layer of mucus covering up all these structures over here while your sense of smell is dampened it's because they're not able to detect the presence of the odorant molecules and send that information onto the brain so that's cranial nerve number one it gives you your sense of smell cranial nerve number two is your opt or your optic nerves so let's go ahead and fill our notes for that so for optic nerves that one's really easy because it's all in the name it's purely sensory this gives you your vision remember how we had the optical foramen when we had the sphenoid bone in our bone and inner skull it's because your optic nerves went through them this is going to give you your sense of vision so if you cover your left eye and you can see through your right or if you cover your right eye and you see through your left just fine then your optic nerves are working just fine optic nerve sometimes gets confused for the next one roman numeral 3 ocular motor but look at the name oculomotor so it's actually an eye mover optic lets you see three oculomotor as you move your eyeballs you actually have several eye movers so i'm going to switch the power point in just a bit and i'm going to highlight three let me highlight this four and we're going to skip five for now so we're going to skip five and we're going to go three four and six and looking at these eye movers so let's go back to optic so here are your optic nerves and so remember the whole contralateral control thing see the crossing over that we see over here in the picture we are going to allow for one side of the brain so the right side of the brain is actually seeing what this this opposite eyeball is seeing versus this right eyeball is actually sending information to the left side of the brain but these are all purely sensory i highlighted it i i highlighted three four and six because they kind of have similar overlapping functions with each other three is oculomotor it does not let you see instead it lets you move the eyes motor means to move and so if you're able to move your eyeballs around if you're able to raise your eyelids and focus on objects from far away or nearby you can constrict your pupils then oculomotor is working just fine and if we look at so number three is oculomotor if we look at four trochlear trochlear is also an eye mover it does control one of your eye muscles so here are your eye muscles it's being controlled by the trochlear nerve but so is six so let's skip number five and six is also an eye mover six will also control just a different eye muscle and so if you're able to move your eyeballs around then three four and six are working just fine so three does a couple different things so it does control eyeball movement eyeball movement it is an eye mover after all in addition to that it does a couple different things it also raises upper eyelid and it also it controls your ability to focus so constrict if i can spell that right constricts pupils pupils are the holes in your irises the colored portion of your eye that lets the light through you can open the pupils up dilate them you can constrict them as well so you have muscles in your iris that's supposed to allow for the opening in constriction oculomotor controls those muscles and so it constricts pupils and controls high focus so your ability to focus on objects nearby or far away part of that is controlled by your oculomotor nerves trochlear is going to be have some overlapping function so i'm actually just going to copy paste that so number four is trochlear that's an eye mover number six abducens is also an eye mover and so three four and six all move the eyeball but as i mentioned three has a couple extra functions so i skip number five number five is the trigeminal nerve tri tells you that there's three branches of this trigeminal nerve it's a mixed nerve so that means it has both sensory and motor functions it can feel things but it can also move things so there's going to be three branches to trigeminal v1 oops let me fix this v1 oops v1 v2 and v3 so the three branches of roman numeral five trigeminal nerve are v1 v2 and v3 the v1 branch this is going to be your ophthalmic branch and it did not spell that right so let's go ahead and let's fix that so you have an ophthalmic branch so that's going to be going to the eye v2 this is also going to be known as your maxillary branch and v3 this is going to be your mandibular branch so this is going to be the three branches part of it so remember they're mixed part of it is sensation can i um feel my face around my maxilla can i feel my jaw around my mandible but they're also motor so they can move a lot of these muscles as well especially when it comes to mastication and so these are the branches that are mainly for facial sensations so let's put this over here mainly for facial sensations so i can feel my space but some of it is motor as well so we can use it for mastication okay so let's go ahead and look at a picture showing your v1 v2 and v3 so it's called trigeminal because you've got three branches coming out of it so from your pawns here's the pawns of your brainstem we're going to have the trigeminal nerve coming out you have an ophthalmic branch that's going out this way can you feel your forehead can you raise your eyebrows up and down because of this branch over here or v2 your maxillary branch can you feel your cheeks can you feel this part of your face you have a mandibular branch so we're going down into the mandible can you feel your jaw when you touch your face interestingly if you've ever had dental work done ever have um ever have maybe cavities filled in in your molars and they take a really big needle needle and inject it way in the back of your jaw what are they trying to numb it's actually this nerve over here if we can hit this nerve and numb it you won't feel your teeth over here so that's what they're aiming for it's actually v3 it's a branch of v3 that's going to be innervating those teeth and so can you chew your food can you feel your teeth can you feel your jaw so facial sensations are basically given to you by the trigeminal nerves so we just did numbers one through six abducens is six we already saw that we're gonna go into number seven seven are the facial nerves so look at five and seven these get confused with each other a lot so for five five is mostly for facial sensation so let's go to our outline for that so can you feel your face that's going to be for number five trigeminal but can you move your face if you can move your face that's going to be your facial so they are both they both have mixed sensory and motor function but this one is mainly for facial movement or meaning your facial expressions can you smile right now can you frown can you make a face all these things are given to you by your facial so for the facial nerve it's also both trigeminal is also both but it's mainly for feeling versus mainly for movement so this one also has branches so while trigeminal has three branches there's a couple more branches that we have for the facial nerve so learning the branches of your facial nerve are actually quite easy because these are terms that we've seen over and over again from the very first chapter and even in our muscles chapter our branches are going to include a temporal branch a zygomatic branch a buccal branch buccal just means cheek a mandibular branch and a cervical branch coming down and so if you know your anatomical terminology you'll be able to tell the branches of the facial nerves really really easily so just as this picture is trying to represent the five branches are temporal right here going on to the temple of the forehead zygomatic a branch that's going over the apple of your cheek buckle buckle means cheek so that's the main part right over your where your masseter muscle would be one going over the mandible so you have a mandibular branch another one that's going to form a cervical branch so if you can move the muscles of your face if you can have some sensations then your facial nerves are working just fine so that was number seven now let's go on to number eight for number eight this is your vestibulocochlear vestibulocochlear can be broken up into two parts anything that's vestibular in nature pertains to balance cochlear on the other hand pertains to your hearing so the vestibulo vestibulo portion is your balance and sometimes it's also termed your sense of equilibrium these are nerves that are going to be found running into your inner ear so you have inner ear structures that will report back your positional changes to your brain and so that's that's going to let you know where your location is relative to the rest of the world for people who have vertigo for example or they have motion sickness there's something going on with the vestibular cochlear nerve where we lose that equilibrium the cochlear part pertains to your hearing we have these inner inner ear structures called the cochlea and the cochlea is going to be attached to a cochlear nerve and that's going to let you hear the world around you so if you've ever heard of someone needing a cochlear implant that's because they may have been born with with a loss of hearing or no hearing at all and so you replace that so that you do have that sense of hearing so let's go ahead and look at the picture for cranial nerve number eight so for cranial nerve number eight you have two parts vestibulocochlear this is the vestibule of your inner ear see how it has these loops called semicircular canals attached to it there's special sensors in these canals that give you like an xyz plane that report back your position relative to the rest of the universe that's going to be attached to a vestibular nerve this snail shaped structure see how it winds around this is your cochlea the cochlea is what's going to be giving you your sense of hearing it's attached to a cochlear nerve the vestibular nerve and the cochlear nerve merge with each other when they merge they're going to form vestibulocochlear so vestibulocochlear is cranial nerve number eight that reports back to your brain so now that we're done with number eight let's go on to number nine number nine is glossopharyngeal don't forget that x means 10 so 1 before 10 is 9. let's go ahead and look so actually let's look at the picture before we switch to the outline so glosso means tone pharyngeal the pharynx that's the back of your throat so you are going to have nerve fibers that innervate the underside of her tongue right here and parts of the backs of her throat and so that's your glossopharyngeal for glossopharyngeal let's go ahead and take some notes down number nine glossopharyngeal is a mixture it has both sensory and motor function to it and it's going to innervate tongue so that's the glossa part and the pharynx pharynx is the back of your throat fair rings common mistake is students will say foreign links no no no it's not fair nyx it's fair rings notice the spelling that's the back of your throat and so because it is a mixed nerve it's going to give you it's important for taste important for taste because it does innervate the tongue it's also important for swallowing because it moves the tongue it's got some motor function but it's also important for speech so whenever someone has communication disorders there's many reasons why they may they might require a speech pathologist a speech pathologist can provide speech therapy sometimes it's a muscular problem sometimes it's a neurological issue but sometimes it's both muscular and neurological it's up to the speech pathologist to decipher what's going on with that particular individual and so sometimes there's something going on with this nerve right here that then affects the person's ability to move their tongue and ability to to move that throat to create communication so that's number nine so let's go to number 10. number 10 is the vagus nerve notice the spelling v-a-g-u-s not vegas the casino with the show girls is vegas with a u so the vagus nerve is a really important nerve don't ever forget the vagus nerve because you're going to keep seeing this over and over again in a and p2 this is the longest cranial nerve that we have this is super super long because it's going to emerge from the brainstem but it goes all the way down your thorax and all the way down into the abdomen and beyond it's a really long nerve so the vagus nerve so let's before we take down notes let me show you guys how how long this is it's a really long nerve that's going to be mixed it's got both sensory and motor functions to it from your brainstem so from your medulla oblongata see how it innervates the back of the throat it innervates the neck region it travels all the way to down to your thoracic cavity see how it talks to your heart and your lungs it talks to your guts in your abdominal cavity so that means this nerve goes past the diaphragm and into the abdominal pelvic region so this vagus nerve has a lot of jobs to do especially when we get to a and p2 when we get to the cardiovascular system the respiratory system and the digestive system so for the vagus nerve because it does innervate the back of your throat it does help with swallowing so control swallowing so 9 helps 10 as well in addition to helping with swallowing don't forget that it also goes into the thorax so it helps with heart rate so hr is heart rate it helps with blood pressure so they're connected with each other it helps with your breathing rate because it does talk to the lungs as well and it goes all the way down into the abdominal pelvic region so it helps with digestive activity as well so that's your vagus nerve for both sensory and motor functions it's going to help control all these different functions so number 11 so 1 after 10 is accessory it's called accessory because it's accessory to the vegas that's where it gets its name but number 11 is mostly motor this accessory to the vegas it helps so it's a helper it's an accessory it helps so it helps the vegas helps the vegas to control the pharynx so part of it does go into the throat um so while your vagus helps with swallowing so this number nine 11 helps with that as well so for swallowing for voice production your voice box is called larynx so swallowing for speech um but it actually goes beyond the inner parts of your neck in addition to helping the back of your throat to produce vocal sounds to produce to give you the ability to swallow it also innervates your trapezius and sternocleidomastoid so not only does it help internal structures of the neck but it also helps with muscles as well so let's go ahead and look at number 11 in the picture so number 11 is the accessory to the vagus the vagus does innervate the back of the throat so when it innervates let's go back to 10 when it innervates the back of the throat it does help with swallowing but so does number 11 so that's why it's called the accessory but in addition to controlling your pharynx your larynx your vocal production your swallowing it also innervates your trapezius muscle it also innervates the sternocleidomastoid so if you can move your head around then number 11 is working just fine if you can shrug your shoulders up and down if you can rotate that scapula then number 11 is working just fine the last one is number 12. number 12 is hypoglossal so we saw glossopharyngeal earlier phosphopharyngeal was number nine and so glosso means tongue so hypoglossal means under tongue so these are other branches these are other nerves that also innervate the underside of the tongue this one's going to be motor and so since it's motor it's going to be innervating the muscles of the tongue there's many reasons why we need a very movable tongue hypoglossal is going to move the tongue muscles and as i mentioned it's got many reasons for doing so mainly it's very important for speech so when you think about making the sounds that you make when you're talking pay attention to what your tongue is doing it's going to be hitting up different parts of your palate it's going to be moving around different parts within the oral cavity to produce the sounds that you make so a good example would be think about what sound the letter t makes so when you say the letter t you say did did the tip of your tongue hit the palette the roof of your mouth or or go ahead and roll your r's what does your tongue do and so those tongue muscles were able to produce these different vocalizations but you also needed to swallow so in case we've never noticed how important tongue movement is for being able to move our food around our fluids around take a big gulp of water when you take a big gulp of water notice how your tongue has to move superiorly against the palate of your mouth and as it moves superiorly you're going to notice that your tongue is going to push the fluid to the back of your throat and that's how you swallow and so your ability to move these muscles is very important so that's what hypoglossal is all about so we just finished all our 12 cranial nerves so you're going to have to remember their roman numerals you're going to have to remember their names and you're also going to have to remember their functions the b or the m or the s is going to help with those functions so sometimes in a clinical setting someone will say oh so and so has cranial nerve 9 palsy palsy just means there's a dysfunction you don't have time to google something and say which one was lying it's like you just have to know and so make sure you remember the number the name and the function for each one