so we finish our journey through the brain with the cranial nerves which because these are nerves meaning they're traveling outside the central nervous system they're not really part of the brain part of the peripheral nervous system because they're carrying messages to the brain or from the brain to the body but this is where it makes sense to talk about them so let's do cranial nerves starting with looking at this pair of images here's a stylized version of the inferior aspect of the brain and you can see here there are some blood vessels as well but there's nerves branching out in all these different directions from all these different places and in fact there is plenty of organization here it just takes a while to really get to know and believe that and it always impresses me to think about you know how we've learned so much about the brain when it's such a mess and you got to rip it out of the body to see all this stuff but we do know about all these cranial nerves we can give them all names and you will learn them all and where they are you can do it it looks like a mess now but let me just show you a thing or two quick oh this starts with Oh olfactory and then this starts with oh optic and then this starts with O oculomotor so just right off the bat coming down the midline oh oh oh those three I'll start with oh the next two start with T there's trochlear and trigeminal but once you get used to those words it's gonna be really obvious like is this trigeminal with the three big branches or is this trigeminal with the one branch right and of course tri means three so this is trigeminal and you know things get busy down here but again there's more tricks to tell all these nerves apart you just need to spend the time with them so 12 pairs of cranial nerves they're coming out of the brain or you could say they're going into the brain depending on which way the information is going and innervating the the local area mostly not to be confused with 31 pairs of spinal nerves that we talked about previously but they're pretty similar right same their spinal cord is part of the central nervous system so the nerves that are attached to it are part of the peripheral nervous system and in this case our pairs of cranial nerves are numbered from 1 to 12 but note the use of Roman numerals that is a requirement for naming these cranial nerves so you can see here they've used n and then the Roman numeral or often you'll see C N for cranial nerve and then the Roman numeral you are going to need to know those Roman numerals so if you're resting on that now's the time to brush up so let's just run through our 12 sets of cranial nerves cranial nerve one olfactory the sense of smell so when you breathe in air through your nostrils you've got this mucousy surface up here called the olfactory epithelium that's where your sensory receptors are for the sense of smell those nerve fibers carry the information into this olfactory bulb into the olfactory tract and up into the brain remember this into the temporal lobe because the temporal lobe covers the ears on audition is processed there and also does the sense of smell so those olfactory bulbs and all factory tracks or are all you can see of the olfactory nerve which is really kind of down here and embedded in your boy bone Oh cranial nerve number two is the optic nerve so you've seen the X shape perhaps in other images this is where the optic nerves cross over each other because as we've talked about the brain hemispheres operate contra laterally so on the opposite side of the brain information is processed so this is the optic nerve carrying the information from the retina towards the brain this crossing over is called the optic chiasm and then the information continues now we're going into the brain we're like part of the brain now and that's the optic tract and then that information will zoom down to the occipital lobe cranial nerve three oculomotor so it's motor moving the eyes controlling both the extrinsic and intrinsic eye muscles I know you might not know what that is yet but in this unit we'll also cover the eye and we'll talk about these muscles but it just means these muscles move the I like to look around and these muscles move the eye from the inside meaning to make your iris constrict and relax to change your pupil size and to bend your lens so you can see close up and far away so all that movement inside the eye is from the oculomotor nerve the trochlear nerve is a nerve that innervates a specific eye muscle one of the extrinsic eye muscles called the superior oblique so if we translate that on the top of the eyeball coming at a diagonal is an eye muscle called the trochlear muscle clear integrated by the trochlear nerve and trochlea means pulley you might remember that from the skeletal Anatomy in the elbow so if you look here I put this arrow the trochlea is this little pulley this little piece of connective tissue here and it causes the superior oblique muscle coming in at an angle to go around this curve to form a pulley cranial nerve 5 is the trigeminal nerve so note that try so there's three branches to the trigeminal nerve the ophthalmic is going towards the eye so it's sensation of the eye and the skin around your eye socket into your lacrimal gland the maxillary branch as the name suggests goes to the maxillary area so it's your sensation from your teeth mouth and nasal sinuses and the mandibular branch is mixed so meaning these branches carry sensory information the mandibular branch carries both sensory information from the mandible like the tongue and lower jaw but also motor commands are sent to the muscles of mastication from the same nerve cranial nerve 6 is the abducens back to the eye you know if you're not sure about what a cranial nerve does if you guess that has something to do with the eye chances are you'll be right lots of muscles are innervated through shared nerves or sometimes their own nerve like abducens the lateral rectus I muscle is innervated by this nerve cranial nerve 6 so lateral rectus if we translate that it means off to the side there's a straight I muscle the lateral rectus or if this is how they cut it so here's the lateral rectus muscle has been cut away but it would be right down here the name here abducens actually tells you what will happen when this muscle contracts so if you have a lateral rectus muscle that's out here if the muscle shortens it will pull your eye away from the midline of your body which is kind of like abduction your muscles cranial nerve facial has motor nerves that go to the face lacrimal gland and salivary glands but also sensation from the tongue so this is another one of these mixed nerves and there's actually a bunch of branches to this going all different places of your face cranial nerve eight is your vestibulocochlear nerve it's quite a mouthful but after we do the ear lecture this will be a piece of cake you'll know all about the cochlea and how it gives you your sense of hearing you'll know about the vestibule and how it gives you your sense of balance in equilibrium and this nerve name has just combines those two so it carries all of your hearing and balance information in one nerve stimulate Oakley innervate cranial nerve nine is glossopharyngeal so glosso referring to the tongue pharynx is in your throat so it provides information on taste and swallowing 10 Dan Vegas yeah Vegas eh es Vegas is a special cranial nerve not just because it's nerve 10 with the big X but because unlike those other cranial nerves it's leaving the head that's going out to all of these different organs here all through the thoracic and abdominal cavity and it's doing a bunch of stuff with the autonomic nervous system to just take care of a bunch of stuff that you know you don't want to even know about yeah all this automatic stuff and tweaking these different organ systems is handled by the vagus nerve now we're in getting into 11 and 12 the accessory and hypoglossal nerves are both muscles muscle control of the head and neck and the tongue respectively hypoglossal meaning under the tongue which is where you'd find that nerve and 11 and 12 we're done so 12 pairs of cranial nerves you do want to know their names of course optic nerve vestibular cochlear nerve you want to know their numbers remember we're talking to rate Roman numerals here you want to know do they carry sensory information motor commands or are they mixed that they carry both now most of these if you know their function you already know what they carry meaning the optic nerve what's its function plus brings information from your eye into your brain so that's sensory information the oculomotor nerve though its name tells you it moves the eye so that's a motor command so it's a motor nerve olfactory is the sense of smell so it's sensory trochlear and abducens control eye muscle movements those are motor yeah vestibulocochlear we said that's the sense of hearing and balance so it's sensory so if you know the function you'll know how to answer this question but you also want to know the origin and destination if you know the function this is gonna be not so not so bad origin and destiny so let's say with the olfactory nerve cranial nerve number one olfactory nerve its origin is the olfactory epithelium that's where your sensory receptors are for your nose and the top of your nasal cavity we have sensory receptors in your olfactory epithelium the destination is well where is that sensory information going it's going to the temporal-lobe to be processed optic nerve the origin of that information is your retina where does sense through the visual information get processed mainly the occipital lobe that's the destination oculomotor abducens trochlear all of those are moving eye muscles so the destination is going to be the eye muscles that are getting moved the origin is what well if I move my eye muscles around right now I'm deciding to move them so voluntary motor controls originate in the primary motor cortex of the frontal lobe so that's the origin for those so again learning the functions which is what's really focused on in the previous slides is going to in most cases just hand to you whether they're sensory motor or mixed nerves and their origin and destination one other thing we need to know is how do these nerves exit / enter the brain because I got to get through the skull so they got to go through some of the holes in the skull but before we look at that realize also that there are other things out there to help you besides the power point so olfactory optics oculomotor Oh once one and then we do takes the Anatomy final pace its trochlear it kind of hides off to the side on the midbrain B is trigeminal three branches so we're not surprised to find it's a big fat nerve Anatomy ah started with a and I say ah because it helps me remember that this is an a cranial nerve and this is H in other words remember I said we kind of go in order but these are an exception and the way I remember which two are over here in the middle instead of being off to the side as I remember ah we Factory that's hard to get out of okay so you can watch that video the point is there are some tips there on the location of the different cranial nerves so that you can get through the lab portion as well some other help would be these mnemonic devices so you heard me referencing this Oh once one takes the Anatomy final very good vacations await hooray so that's all shown here now it's not the best mnemonic device ever there are others here about hamburgers and stuff I guess the reason it's not the best is Oh once one they all start with oh but you still have to know that will factory is first and then optic and then oculomotor but it gives you the first letter at least so you can use that you can look up other mnemonic devices of course just Google and mnemonic cranial nerves you'll get a bunch remember you also want to know if these are sensory nerves motor nerves or both meaning mix with sensory and motor so there are also mnemonic devices for that some say Mary money but my brother said big business makes money that's fine or I think better some say Mary money but my brother said big brains matter more or big butts or whatever you want to put in there that will help you remember it again you can google this and they just there's just awful stuff other people are just sick you know but whatever gets you through you know nursing school so use these mnemonic devices to help you with these cranial nerves and then to know how these nerves enter / exit the brain how do they get through the skull this list looks pretty intimidating I don't have any fancy mnemonic devices to get you through this but I don't want to walk you through it because a lot of these makes sense meaning if you remember your skill anatomy you know that there are little holes called the cribriform foramina in the ethmoid bone so cranial nerve one is the olfactory nerve so it has to go through the cribriform for a minutes what they should say in the cribriform plate to get to the brain you also should remember the optic canal through this fee known and then you've got cranial nerve three oculomotor trochlear it controls the I try geminal which has the ophthalmic branch going to the i/os one take C and then of the abducens another I one so all of these have something to do with the eye so make sense you've got that big fissure right up at the top of the orbit that all of them use I remember trigeminal means three branches so you've also got these other two branches that are taking different routes through the skull and I don't have any help to remember this except just brute memorization but it does make sense that the ophthalmic branch hangs out with the other eye nerves and goes through the super orbital fissure the other branches go through these other holes when you get to the internal acoustic meatus cranial nerve eight vestibulocochlear makes a lot of sense right because this is like our inner ear hole and this nerve carries our hearing information but cranial nerve seven is our facial nerve so you just have to remember the facial nerve piggybacks with the vestibulocochlear nerve through this meatus and we said the facial nerve has a bunch of branches we weren't worried about so it also needs a secondary hole the psycho mastoid foramen now when you get towards the bottom you're kind of towards the back of the brain more get near the jugular foramen that's a big hole for the jugular vein but also you can fit a whole bunch of nerves in there yeah so you just throw in or 9 or 10 or 11 and then your last cranial nerve is the hypoglossal nerve and in the occipital bone we have a little hole called the hypoglossal canal or hypoglossal foramen so one last little nerve that's happy little home and that's the end of the brain and cranial nerves