DIP Episode 133 - USMLE Step 1 Neuro Review 3 (Cranial Nerves)

Okay, welcome. My name is Devine. I am a resident and this is the 133rd episode of the Divine Intervention Podcasts and in this episode I'll be continuing my USML is step one in your all-year review. So this will be a newer review three and my focus today is going to be on the cringoners. Okay, this will probably extending to the next podcast because I can already see how this could go for really longer period of time. But yes, in this episode I'll be talking about the cringoners, right? I mean anyone that has taken step one, you already know that the cringoners are high-yield to know, right? Like there's literally gonna... You're gonna find cringoner of questions on your exam if you don't... If you don't know about the cringoners, you really shouldn't be taking step one, right? Maybe not the best idea in the world. Okay, so let's jump right into it. So I'm going to approach the cringoners from multiple angles. I feel like the thing that makes people freak out with cringoners is they just don't have the information well organized. If you have the information well organized, you notice that you actually do a lot. They actually not that hard to remember. I mean like really the way that I thankfully still remember the cringoners in great detail. To this day, yes, obviously from like tutoring and all that stuff, but also just having good organization from the get-go. I think that helps tremendously on exams.

So before I even jump into the first cringoner, I'm going to talk about some groupings that I just really feel would help tremendously on a test. And then one of the things I also plan to do is in the future I plan to make because I know that also for just meds to then just starting out med school when you're doing gross anatomy. Cringoners are a bear to learn. Right. So I plan to for sure in fact in the very near future make like an actual cringoner of podcasts, but that's targeted more for people in med school. Not necessarily people taking step one. So I'm going to like more extreme detail compared with what I'm going to go into detail on now. For this because I initially thought of making one podcast that will satisfy the needs of a med student in a gross anatomy course and also like a med student in a in a taking a taking step one, but the overlap. Yes, there's overlap, but there's a lot of stuff that I feel like will be agonizing for step one person to learn. So I'm just going to separate both. So I'll make like a dedicated cringoner podcast just for medical students. I'm hopefully I should have that out within the next few days. So let's go ahead and let's go ahead and begin. So the first thing you want to keep in mind with regards to the with regards to the cringoners are that you want to you want to first be able to make sure that you are able to integrate them with clinical syndroms. That is what a lot of your friends at the MBME test on exams.

That's the first thing. The second thing is in fact, I guess this is well, formally start right is you want to be able to group your cringoners into a cringoners being model or cringoners being sensory right because the thing is there are some cringoners that are purely motor right. There's some cringoners that are purely sensory and then there's some cringoners that are mixed right. So they have both motor and sensory functions and the thing is the mixed cringoners it's actually kind of easy to remember which is which because they are the most complicated nerves right. I mean like if you remember back from like your first year learning gross anatomy you probably agonized just really think about it. What were the cringoners that had the most branches the most pathways the most pain or headache from learning right that's like 5, 7, 9 and 10 right. So 5, 7, 9 and 10 right. So like you're trying to get an owner of that's cringon 5 your fish on her that's cringon 7 right. You're glossifying geo nerve cringon 9 and then your vigus nerve cringon 10 those are the most agonizing to learn right. So it will make sense that those should be mixed cringoners the agonizing because they just have too many things going on and then there are some cringoners that are purely model okay. Cringoners they're put purely model and really the way to remember them is just remember like 3, 4 and 6 and then 11 and 12 right.

So like ocular model, trochlear, abducense, spinal accessory and hypoglossal right. And the thing is it's actually very high yield to one like there are some foundations I want to learn this in this podcast right. It's actually very high yield to know that the purely model cringoners have found immediately in the brain stem. It's very important to remember that there is an embryologic reasoning behind that but I'll discuss that in a different podcast. Again I don't want to cause a brain overload here but the model cringoners remember M4 model M4 media. They found immediately in the brain stem. There is like some weird stuff with like basal plea, iler plea and all that that's kind of like the embryo logic embryological undertone without talking about that leader. And then there are three purely sensory cringoners and the way to remember them is just remember the number 128. Okay. The one is for the is for the olfactory nerve right. The two is for the optic nerve and then the eight is for the vestibular ococular nerve. Basically the nerves that the cringoners that carry like special sensation right. They do they are for the most part purely I mean purely sensory right. And if the purely model nerves cringoners were immediately in the brain stem, it should make sense that the purely sensory cringoners should be lateral in the brain stem.

And then the mixed cringoners which are essentially like the again like your 5, 7, 9, and 10, those should lie somewhere bit like they should be like medium lateral. They should be between the purely media of the motor cringoners 346 and 12. I mean 346 11 and 12 and the purely sensory cringoners which are one, two and eight. Okay. So again very high you to remember these. And then also one thing that would also help with understanding the cringoners as we proceed is remembering that the cringoners right they do carry some autonomic nervous system fibers right. So just kind of like a quick summary of the autonomic nervous system I would hope that you remember that your ENS controls like most of your visceral body functions right. And we already know that we have like the somatic nervous system right. Remember that's like a one-year-end system where you essentially go from the anterior horn right like the ventral horn of the spinal cord to skeletal muscle. But the ENS right is a two-neuron system right. The two neurons is like you have one neuron and then you have a second neuron and those two neurons are separated by a ganglia. Okay. And remember right you autonomic I mean your somatic nervous system like the anterior horn I would hope that you remember like your anterior horn diseases right. So like spinal muscular atrophy right where people have like mutation chromosome 5 but it was more recessive inheritance with the survival motor neuron 1 gene right.

So they'll describe a kid that's like less than a year old with like fast calculations losing motor milestones and sort of deal right. And then hopefully you also remember that polio right then West Nile virus torch the anterior horn of the spinal cord. So so that's your somatic nervous system but again your autonomic nervous system it's a two-neuron system. The first neuron is the pre-ganglionic neuron. The second neuron is the post-ganglionic neuron and again I said those two neurons are always separated by a ganglion right. So she kind of makes sense that one is pre-ganglionic so prior to the ganglion and then another should be post-ganglionic so distal to the ganglion. The ganglion is kind of like the middle man is like the go-between between the pre and the post-ganglionic neurons. And the thing is right your parasympathetic nervous system right. The pre-ganglionic neuron right so the first neuron is long right. Because if you kind of think about it the middle man for the parasympathetic system the ganglia is located in the walls of organs right. And these cranial nerves I mean these are these are these are parasympathetic nerves for example and like the pre-ganglionidial kind of studying like at least for the vagus nerve that's more like in the in the bris stem but the all kind of start like in the spinal cord right. So if you want to travel from the spinal cord all the way to the wall of an organ to medial ganglion to medial men right.

That means you have to travel out pretty long distance for that to happen right. So the thing is in the parasympathetic nervous system the first neuron the pre-ganglionic neuron is long again because it has lots of grounds to come like lots of ground to cover before it gets to the associated ganglion right. And then the post-ganglionic neuron is short because it just needs to go from the wall of the organ to somewhere inside the organ okay. That is really all I want you to remember if you remember that then just take the opposite and you already know that what the sympathetic nervous system should be. The sympathetic nervous system has like a short pre-ganglionic neuron right and a long post-ganglionic neuron right. Because remember for your sympathetic nervous system the ganglia lie very close to the spinal cord right. So in fact those ganglia call like paravertibral. So paravertibral means juxtaposed to the tibral bodies right. So paravertibral ganglia right. So the pre-ganglioners don't need to travel that far to get to the middlemen to get to their goobytwin which is which are the paravertibral ganglia. Now so how does your autonomic nervous system relate to the crinioners right. So the thing is some of your crinioners the carry autonomic nervous system fibers right. So and for the most part these are usually parasympathetic fibers that they carry okay.

So again the big crinioners that carry autonomic nervous system fibers again especially parasympathetic crinioners 3, 7, 9 and 10 okay. So 3, 7, 9 and 10, 3, 7, 9 and 10. So like your oculumurinerv like your facial nerve your glosopharyngeal and your vigus. And just for purposes of again people taking step one listening to this podcast. This is not related at all but maybe this is a way you can remember two things at once. If you substitute that three so I just say three seven nine and 10. If you substitute it the number three for the number two you are left with two seven nine and 10. Those are actually the and then I guess if you are protein CNS those are the things that are gamma caboxylithead by vitamin K epoxide reductase okay. Those are the clotting factors that are gamma caboxylithead by vitamin K epoxide reductase but that's like warfarin business and all that stuff but I just thought I guess I'll go ahead and through that in there. So your aeronomic nervous system again like I said mostly parasympathetic fibers that relate to the cranial nerves there is some weird sympathetic stuff but I think I should maybe talk about that later so that I don't confuse you.

And the thing is the cranial nerves right that carry parasympathetic like parasympathetic like ganglia right you want to kind of know the associated ganglia for those parasympathetic functions right so for example like cranial nerve three you want to remember that it deals it has like the ciliary ganglia right for cranial nerve seven I want you to think about the terigo palatin and the sub mandibola ganglia okay and then for cranial nerve nine I want you to remember the oric the oric ganglia okay so cranial three ciliary cranial seven has two like parasympathetic associated ganglia right so like terigo palatin sub mandibola and then cranial nine is the oric is the oric ganglia right and then remember cranial ten is kind of special in its own right vegas nerve goes to many visceral organs for the most parts those ganglia like the associated ganglia and the walls of organs and then one of the high yield thing you want to know your cranial nerves right you want to know where the nuclei are located and really the easy way to remember this is to just go ahead and start from the medulla in series of fours and just count upwards right so it's like your medulla right the cranial nerves like nine through twelve so like nine ten eleven twelve so glossopharyngeal vegas spinal accessory and hypoglossal the cell like they're nuclear right they're all in the medulla right and then cranial five through eight right so counting up the next four so like cranial five trigeminal cranial six abducense cranial seven facial and cranial eight vestibulococlear those have the acel bodies in the ponds and then cranial three and four they have the acel bodies in the in the midbrain right they have the acel bodies in the midbrain and remember that I think cranial one right cranial one and two they're less they are not much in the way of a brain stem associated with a cranial nerves if you want to

put it that way and I'll see some special like embryologic stuff about cranial two shortly and one thing I want to say about those pontina cranial nerves right so cranial five through eight the thing is cranial five it's like the main pontine cranial nerve the trudey is cranial six through eight like six seven and eight those actually have found more like at the cerebellum I mean at the at the corticometallary junction right so sometimes you may see people that have like medulla associates and drums having like some pontine cranial nerve deficits the reasoning behind that is that the medulla like the junction between the medulla and the ponds actually is where cranial six through eight for the most part stand right and I'll say again I'll say some more near an atomic host of abduza as we go along and then there are some laws this is more for people that are taking people that are taking a gross anatomy course but I think this will also help someone step one for like the oddball question or two where you do need to keep some things at the back of your mind the thing is there are some laws known as sterns so STERN sterns laws they help you remember certain muscles that are innervated by certain cranial nerves right so the thing is these sterns laws are kind of like the solubility principles you may have learned in undergrad when you were learning like oh if like you you probably learn like six or seven solubility rules that oh if the cadaion in a salt is a group one element so like sodium or potassium or whatever then that salt is always soluble or whatever right and then oh there's row two but you should only apply row two if you've already applied row one or if row one doesn't count that's kind of like the same thing with these sterns laws there's three of there's three of them the sterns laws basically stay that so row one right is that if any muscle is if you have

a tensor in the name of any muscle that means he must be innervated by the third branch of the trigeminal nerve that's like cranial v3 that's the mandible nerve okay and then row two is that if you have any muscle that has the like word palat in its name then it's already that means it's innervated by the vagus nerve okay so um so like any muscle that has palat in its name is an evaded by the vagus nerve but that's only if row one but row one essentially precedes row two and then row three and I'll give you an example of this row three if any word if any muscle has glosses in its name that means it's innervated by the hypoglosal nerve right cranial nerve 12 and it's only superseded by rules one and two right so I'll give you a classic example like palato glosses right palato glosses is so you see glosses in the name it's actually not innervated by cranial 12 it's actually innervated by cranial 10 okay the vagus nerve right and the reason again palato glosses palato glosses right around the palate glosses right is row two precedes row three right so palato glosses believe it or not is actually innervated by the by the vagus nerve and then um some big things I guess you want to also keep in mind with the cranial nerve that you'll know like your holes right you want to know certain things that traverse certain holes right so unfortunately this is just flashcard material this is just very unfortunately something you would have to commit to commit to memory right so um like your gridter patroso nerve right you want to know that it goes through what for emin for emin last term okay um your mandibola nerve what does it go through your for emin ovali right okay how about your factory nerve right that'll be your cribber from pleating the ethmoid bone right so your cribber from pleat ethmoid bone is traversed by cranial one remember if you have like a cribber from pleat fractur

e that can cause an osmia right and then your internal corroded artery what does it go through go through your corroded canal right that's kind of easy to remember how about your hypoglossal nerve again this one is also easy hypoglossal canal right and then how about your middle meningel artery what does it go through it goes through for emin it's been no some right remember that your middle meningel artery right it kind of runs through the temporal bone as well um whenever you fracture a temporal bone you scrub the middle meningel artery that can cause an epidural hematoma okay now how about like your cranial seven and eight so you're official and your vestibulococliners what do they go through well that's the internal acoustic mellitus right and then how about like cranials three four v one and six so like your oculumodoneurve your trochlear nerve your thalmic nerve right that's the first branch of the trigeminal and then the abducins nerve what do the traverse I hope you're saying the superior bit of fissure okay that one is especially high yo-to-no for exams and then what is the hole so basically if you take all I just mentioned in the previous sentence and then add cranial v two right so like the um the maxillary nerve um what holds all those thin strivers I hope you're telling me the covering of sinus right it is floridly high yo-to-no what goes through the covering of sinus and it's floridly high yo-to-no what goes in the wall versus what goes in the middle right so like cranials three right so your oculumodoneurve cranial four your trochlear nerve cranial v one your thalmic nerve cranial v two your maxillary nerve and cranial six you have two sense nerve those all traverse the traverse the covering of sinus and then cranials nine through sorry remember that v two the maxillary nerve does not go through the superior bit of fissure okay but the maxillary nerve g

oes through the covering of sinus okay it's only v one v one the ophthalmic nerve is the only branch of the trigeminal that goes through the superior bit of fissure okay now um how about like cranials nine through eleven so like your glossopharyngial your vigus and your spinal accessory what what uh what uh hold do they go through well I hope you're telling me the juggler for email right remember your sigmoid sinus also goes through um even your inferior petrosal sinus the inferior petrosal sinus is kind of high yo from the standpoint of inferior petrosal sinus sampling I'll talk about that in an indoctrin review down the line but yes uh those all traverse your juggler for email and then your maxillary nerve right I said your maxillary nerve goes through the covering of sinus but remember it also goes through for email rotundum okay so remember cranials v one v two v three right so v one your phthalmic nerve goes through the superior bit of fissure v two the maxillary nerve goes through for email rotundum and then v three the mandible nerve goes through for email rotundum and then your optic nerve so cranial two the ophthalmic artery which is one of the branches of the internal corroded uh what what what um what what hold us he go through ready goes through the optic canal right and then this one is also especially high of the fissure nerve remember that before the fissure nerve exits the face remember it goes through something called a styloma stoid for email okay the styloma stoid for email this is actually very very high yield to know for exams right so let's kind of talk about that so if you notice you may see divine I thought this was a cranial nerve spot cast yeah I promise you it's a cranial nerve podcast but the thing is again I try to teach things in a way that I'm useful for exams okay so again I think it will be much more useful to learn these groupings bef

ore I then delve into the cranial nerves themselves and when I delve into the cranial nerves there will be much simpler to remember and understand if you have this uh if you have this foundation I'm focusing on right now so the cover nurse sinus right in fact you may be surprised that if you learn these early parts like you may already know a lot about the cranial nerves before you wouldn't jump actually jumping to learning them right so the cover nurse sinus right again like I said it's kind of important to know what goes through the cover nurse sinus um because it's actually clean clear and believe it or not right there's many pathologies of the cover nurse sinus cover nurse sinus thrombosis and all that stuff there's a lot of like high yield things that go through the cover nurse sinus right so like I said earlier right cranial three four V1 and V2 and again repetition always helps if you remember I've said this factor in all like three or four times right so three four V1 V2 and so like again your oculum motor nerve your trochlear nerve your ophthalmic nerve and your maxillary nerve okay the all pass along the lateral wall of the cover nurse sinus okay the all pass along the lateral wall of the cover nurse sinus and then cranial six right so like you have ductions nerve the internal curly lottery the all pass in the middle of the cover nurse sinus okay and again remember all the cranial nerves I've mentioned here with the exception right of like V2 the maxillary nerve they also all pass through the superior orbital fissure okay again very very high yield to know to know that and then let me also see some high yield things I guess about the brinstane right because unfortunately your friends your friends the mbme right they love to give questions relating to the brinstane again like I said I will try to I'll try really hard to finish this cranial nerve podcast withi

n the next like two days or there about right because I think it's just something that I want to just solve one problem I want to solve because again I've gotten a lot of like requests from people to make a cranial nerve associated a associated a podcast right so what are some I guess high yield things you want to remember with regards to the to the brinstane right so this part you really do want to pay a lot of attention right so remember the brinstane right like there is the part of the brinstane that um in fact let me make this super super easy for you the part of the brinstane that faces the face okay him into make that right there but the part of the brinstane that faces the face okay is the is the ventral side okay the part of the brinstane that faces the cerebellum okay is the dorsal side okay so brinstane part that faces the face right so like the one terro part is the ventral side the mobile terro part that again faces the cerebellum all like your oxypat is the is the is the dorsal side of the brinstane so ventral anterior faces the face dorsal posterior faces the cerebellum okay now what are some I guess good high yield things to know about the ventral surface of the brinstane right so let's sort of take it from the top right the thing is and I will go from top to bottom right from top to bottom so the thing is the ventral surface of your brinstane is actually where most of your cranial nerves arise okay most of your cranial nerves the arise from the ventral surface of the brinstane right and remember right we've kind of talked about some high yield things you already right so we've talked about like how the or fracture the your factory nerve right cranial nerve one right it kind of goes through the vibraphone plate of the ethmoid bone on its way to exiting the cranial cavity right and then we've kind of talked about like the optic nerve right remember the o

ptic remember it's kind of called like cranial too it's called optic nerve prior to the optic a chiasm right but after the optic chiasm is called the optic tract okay so prior to the chiasm is called the optic nerve distal to the chiasm is called the optic tract okay and I remember that the optic nerve is actually a derivative of the diene cephalon right so one I guess key piece of embryologic trivia that many people don't seem to focus on for the USML step one is that all your cranial nerves actually derive from the from the peripheral nervous system believe it or not all your cranial nerves this is super high yield you know they are all derived from neuro crest with one exception okay so neuro crest gives rise to all your cranial nerves with the exception of cranial nerve two cranial nerve two is a derivative of the diene cephalon right so if you remember that you already know right of the but that if a person has like a demylineatin disorder of the peripheral nervous system like Guillembray syndrome it should ideally not affect cranial nerve two because cranial nerve two does not come from neuro crest okay so Guillembray syndrome typically does not cause visual symptoms it can but typically on MDM is it does not cause visual symptoms right and all your other like cranial nerve right like your cranial 3 blah blah blah right it should make sense that it should be mylineeted by by schwan cells comparing that's why again because you may wonder hmm how do people get a schwanomas right and you're like oh at the cellular below point in angle well guess what right schwan cells actually exist like within the within the brain because again certain parts of like your head and neck right again are derived from your peripheral nervous system but contrast this with like a disorder like a demylineatin problem of like your CNS right like neuro tube like multiple sclerosis if you n

otice people that have multiple sclerosis they tend to get a lot of like eye symptoms right like interneucleophthalmoplasia or I guess the more paramount one that may be released to the idea I'm trying to get across here's optic neuritis right because remembering MS right they have those people have problems with oligodentrocytes okay because oligodentrocytes mylineet derivatives of your central not peripheral central nervous system okay so if a person has MS right for the most part the cranial nerve that tends to get all bungled up is cranial tube okay the optic nerve because again the optic nerve is a derivative of neuro tube not neurocress is a derivative of the diencephalon okay now if you then I guess jump to the midbrain right so in the midbrain right on the ventral on the on the ventral surface right we have the we have the cerebral pedoncones okay the cerebral pedoncones please do not confuse the cerebral pedoncones with the cerebellar pedoncones the cerebral pedoncones you actually find them anterior like so the cerebral pedoncones you find them eventually in the brainstem so the anterior in the brainstem like in the midbrain the cerebellar pedoncones you actually find them dorsally you find them posterior in the brainstem okay so again I'm just talking about anterior brainstem right now right so we have the cerebral pedoncones remember the cerebral pedoncones the um the essentially have like um those uh because remember your descendant pathway is like your corticospinal tract sort of starts in the cerebral cortex and goes all the way down right the thing is as it goes all the way down right it um um it goes through the brainstem before it decusates at the medallary pyramids right the thing is the as it's going through the brainstem as it's cutting through the midbrain the place it cuts through is the uh at the cerebral pedoncones okay now why is it important

to know about the cerebral pedoncones it's important to know about them because there is like a space between the cerebral pedoncones there's like one cerebral pedoncone on the left there's one cerebral pedoncone on the right between those pedoncones you have something called an intrapedoncular fossa okay the high u thing to know about the intrapedoncular fossa is that uh the cranial uh cranial 3 right so your ocular motor nerve actually traverses that intrapedoncular fossa on its way to the like the superior bit of fissure and cavernous sinus kind of business and then um if you then go to the pond right you have the ponds used like if you remember from gross anatomy the ponds is like this huge bulge right so again i'm talking about the ventral surface right now you have this huge bulge of the ponds that's that's all you need to know about the ponds that huge bulge are just fibers of the corticospinal tract and then if you go to the if you go to the medulla right um the medulla right anteriorly again you just have like your medallery um pyramids okay your medallery pyramids right to remember that's where you have the corticospinal tractor decucity now crossing over to the other side right and again like i said if you're going through the anterior the ventral brings them again like in the midbrain you'll find craniums three and four okay craniums three and four and then in the ponds right again you'll find craniums like six seven eight and no sir you'll find craniums five six seven and eight okay and again like i said if you look at the anterior mid like the anterior ponds right you notice that right in the middle death smack in the middle you have the two abducense nerves right and again it's in the middle because it's a purely model cranium and remember three four six and twelve your purely model craniums and then if you sort of look off to the side if you notice th

e thing that is the cranium that is most lateral in the ponds right is your purely sensory craniums like a cranium eight okay cranium eight is purely sensory right so you'll find it so your vestibulococular nerve you'll find the most lateral in the in the ponds okay but but six and seven sorry yes but six but so six is in the middle eight is very lateral and then in between those you have seven because seven is a mixed nerve it's a model and and sensory right and then remember again like i said six through eight you'll find them mostly at the pontina medallary junction right versus five that is more like rustle it's like a little like more it's like the mainstream pontine cranium or cranium or five because it's so complex right and then again when you get to cranium when you get to the medallary right you have like cranium twelve that's the most medial okay again and again all these things you may say divine why you're harping on medial lateral medial lateral blah blah blah blah I will use this knowledge to teach you a trick for resolving essentially any brain stimulation on the on the USM list step one example it's kind of like a high-altryctinal but it kind of depends on you understanding and remembering some of these roles although to be honest i'll also teach you another rule that me even obviate the need for you to remember some of some of these some of these roles but again having that understanding is what will help you and carry all the way there on step one right so cranium twelve hypoglycemic nerve is purely model so it's the most medial in the in the medallary right again ventral anterior medallary the side facing the face right and then after that we kind of have like a cranial 11 spinal sister nerve cranial 10 cranial 9 again those are all off to the site okay because again those are not purely those are not purely model like the hypoglycemic nerve which

is cranial nerve 12 and then if you're looking at the if you're looking at the at the dorsal brain stem right so you're kind of looking in the back so again like the side that's facing the facing the cerebellum right if you're sort of walking your way down from midbrain down to the medallary the thing is in the midbrain right we have like in the back the big big structures you notice are you notice that we have like four bulges at the back of the midbrain right those are called colliculi right so we have like the superior colliculi and the inferior colliculi right the thing is it's very high yield to remember that the superior colliculi the control like a vertical conjugate gaze right so the control vertical conjugate gaze right so if a person has a problem at the level of the superior colliculi they can have like a vertical deplopia so they have like double vision in the like in the long access right so like when they're looking up or down they have a deplopia so you may ask okay divine what can cause problems with the superior colliculi as well here's what people can have problems at the superior colliculus if they have a pinealoma right a pinealoma right is like a parynoid syndrome right because remember the pineal glands actually lie superior to the superior colliculi let's again I'll repeat that again the pineal gland is superior to the superior colliculus so if a person has a pinealoma right that pinealoma can compress the superior colliculi and that patient will have a vertical deplopia believe it or not that is something floridly high yield that he tests all the time on the USML step one and then if we go so below the superior colliculi we have the inferior colliculi you inferior colliculi the idioma with like hearing right so like auditory sensation but it's actually kind of high yield to also remember something if you go inferior to the inferior colliculi th

at's where you have the trochlear nerve right so remember I said earlier on that essentially all the cream all essentially all the cranial nerves exit from the ventral from the ventral brinstem okay so like the anterior brinstem the thing is the trochlear nerve is an exception to that room the trochlear nerve cranial nerve for exits in the dorsal brinstem okay it exits very high yield to notice in the dorsal brinstem okay so it exits in the dorsal brinstem right so it's the only cranial nerve that does that and the thing is the trochlear nerve is also the only cranial nerve that gives crossed findings okay so if a person has like problems with like the left trochlear nerve they'll have problems like in the right eye okay and the reasoning behind that again is because it essentially crosses in the back and then makes its way to the front to the associated eye right so again so paired to the superior colliculus you have your pineal gland so pinealoma parynotes syndrome sort of business inferior to the inferior colliculus you have your trochlear nerve okay cranial nerve for and again it's the only cranial nerve that exits dorsal brinstem and it's the only cranial nerve that gives crossed findings most cranial nerve deficits are Ipsilateral to the side where you have the deficit but the trochlear nerve is different if you have a trochlear nerve lesion you cause problems controlateral to the to the deficit and then also remembering the midbrain right just in front of the just a little ventral to the superior colliculi you have the pre-tectone nucleus right the pre-tectone nucleus sort of controls your pupillary life reflex I'll talk about those reflexes in a later podcast but basically your pupillary life reflex the afferent part of that reflex is cranial too your optic nerve so your optic nerve brings in information and then from the pre-tectone nucleus it projects bilate

rally to the to the bilateral cranial threes right and then people get all and then you have like the efferent part of your of your pupillary life reflex I'll talk about that later but there are certain problems like argorobrattin pupill and stuff like that that are lesions at the level of the at the level of the pre-tectone nucleus and then if we go downwards to the ponds right the ponds the big things you want to remember here the ponds are where you have the where you have the cerebellar pedoncles so again like I said do not confuse the cerebropedoncles with the cerebellar pedoncles okay your cerebropedoncles are located in the midbrain and the ventral in the brainstem your cerebellar pedoncles are located dorsally or posteriorly in the brainstem and the efferent of ponds okay and then if you go below that right you have you have the what is it called like your medulla right and your medulla like in the medulla there are some key dorsal structures you have right so think about like a truck coming from your spinal cord your dorsal columns right you should make sense that if your dorsal remember you probably know this already that the dorsal columns those fibers synapse in the dorsal in the dorsal like the synapse somewhere in the medulla right but you should make sense if you are called dorsal columns you should make sense that these synapse in the dorsal medulla right again I know neuro has a bad rep amongst the med students but neuro is actually a lot of fun and he's actually very logical if you just think about it for a second so so your dorsal columns right like you probably remember like your nucleus coenitis that is more lateral in the brainstem and your nucleus gracilis which is more medial in the brainstem your nucleus your coenit nucleus and your grisal nucleus they are both found in the dorsal in the dorsal brainstem okay and then like the olives you also

find them in your dorsal brainstem so that's something you want to keep actually I take that back your olives are found in the in the ventral brainstem serve all that so again your your your dorsal columns right like your coenit nucleus your grisal nucleus they found in the dorsal brainstem in fact the medial lemnescus where those fibers like cross right ultimately they keep you see it you also find that in the dorsal in the dorsal brainstem and then like your spinal thalamic tract right that carries like pain temperature and pinprick from your from your pain temperature pinprick from your from your spinal cord right from your periphery right those also run in the dorsal brainstem but again if you think about it your spinal thalamic tract it's a it's a sensory pathway right so again it should make sense that it should run in the lateral brainstem not the medial brainstem just as per the rules I discussed earlier right and then also your your sympathetic nervous system right so there's this then there's this concept of for some reason people seem to get wrong on exams so let's maybe talk about it real quick and again I'm gonna bring this podcast to an end fairly fairly soon right because again this is going along but again even if I've known it expressly talked about one cranio nerve I've already said a lot about the different craniochrania nerves and again all these little like extra stuff extra like understanding stuff that is where the mbmi focus is a lot of its efforts when it's right in a questions but many people think right so if people hear the autonomic nervous system they're like oh my sympathetic nervous system thoracolomba my parasympathetic system cranial sacral like oh those things all starting the spinal cord that is actually not true your autonomic nervous system believe it or not actually starts in the hypothalamus okay so the thing is again I now thou

ght you that the autonomic nervous system is a two-year-end system and that is actually what you should learn for exams but your autonomic nervous system if you really delve deep is more like a three-neuron system because there is an original fiber that sort of starts like you start things in the hypothalamus and then runs down through the dorsal brain stem in the lateral part of the dorsal brain stem comes all the way down and goes to the spinal cord and then innervates those like thoracic and lumbar fibers that are for example the thoracolumbar fibers that constitute a sympathetic nervous system I'll see more about this in the next podcast but it's like you have a fiber going from like the hypothalamus to the thoracic and lumbar spinal cord right so that's like almost like the neuron that no one ever talks about and then those say for example if you're dealing with the face and we're talking about sympathetic nervous system the pre-ganglionic fibers then start like in the thoracolomba cord they go to the superior cervical ganglion right and then from the I guess if you're doing more sympathetic face you're doing more like thoracic as spinal cord so they go to the superior cervical ganglion the ganglion is then the middle man and then from that ganglion you have the post ganglionic fibers that then go to different parts of the head and neck again I'll talk about those things as we as we go to the as we go to the next podcast but I do think you have said enough here but again I promise you folks this podcast is this first one especially is like super super high-youtes to know I know I'm at the 40-minute mark but I don't know like there are some things that are kind of still like noin at my noin at my my mind that I want to talk about should I leave this to another podcast let's see okay you know what let me just see some quick things here and then I'll throw in the ot

her stuff at my my other podcast right so the mid-brain right I already said I already talked about how the superior colliculas inferior colliculas and the mid-brain I remember that the the the substantiant migra right you actually also find it in the mid-brain okay remember if you have the pigmentation of the substantiant migra right that can cause a Parkinson's right and also remember you can destroy the substantiant migra if you if you if you take like improperly cooked like opioids like MPTP right that can cause like a Parkinsonian syndrome right so that's something high-yout you want to keep at the back of your mind for exams and again cranial 3 and 4 you find them in the mid-brain like the eight-injowespawn you close out talk about that in the next newer series right and all that stuff you all find those in the mid-brain and um um uh yeah I think this is going on for too long let me let me pause here we'll continue this in a in a little podcast so as I always do when I end up podcasts right so I do offer one and one tutoring for all the usml exams step one step two ck step two cs step three um and then I also uh tutor for like the pre-clinical med school exams the 30th shelf exams like the clerkships and then um the if you're an internal medicine resident if you need tutoring for the internal medicine like board exam the abi exam and also the intranin exams I do offer tutoring for those and then if you have like a college buddy that um needs tutoring for like physics gen chem ochem biochem physiology histology I do offer tutoring for all those things right and then um um um if you're a college student applying to a med school so like an amcass app or a med student applying to residency right I know this is kind of like application season for a lot of a 30 years right so like an era sub I do offer one on one advice and slash consulting for that so like personal s

tatement right then application mock interviews um again I have a ton of experience I've worked with a ton of people in that process and essentially everyone I've worked with has matched most of them between their first two third choices like probably like 70 80% much that their first choice so take that for what you will so reach out to me anytime um reach out to me either through the website or you send me an email like divine intervention podcasts with an s at the end at gmail.com so have a wonderful rest of your day god bless you I'll see you in the next podcast thank you

CN III, IV, VI, XI, and XII.

The Trochlear Nerve (CN IV). A lesion here causes problems in the contralateral eye.

CN I (Olfactory), CN II (Optic), and CN VIII (Vestibulocochlear). Mnemonic: 1-2-8.

The Pineal Gland. A pinealoma compressing this area can lead to vertical diplopia (Parinaud syndrome).

Parasympathetic has a long pre-ganglionic fiber and a short post-ganglionic fiber. Sympathetic has a short pre-ganglionic fiber and a long post-ganglionic fiber.

CN XII (Hypoglossal Nerve). It controls the tongue muscles.

CN III, IV, V1, and VI.

CN III $\rightarrow$ Ciliary Ganglia; CN VII $\rightarrow$ Pterygopalatine and Submandibular Ganglia; CN IX $\rightarrow$ Otic Ganglia.

Cranial Nerve II (Optic Nerve).

Dorsal Columns (Nucleus Gracilis/Cuneatus), Olives, and Medial Lemniscus.

Middle Meningeal Artery.

Cerebral Peduncles are located anteriorly/ventrally in the midbrain; Cerebellar Peduncles are located posteriorly/dorsally in the pons.

CN III, IV, V1, and VI.

CN III $\rightarrow$ Ciliary Ganglia; CN VII $\rightarrow$ Pterygopalatine and Submandibular Ganglia; CN IX $\rightarrow$ Otic Ganglia.

Cranial Nerve II (Optic Nerve).

Dorsal Columns (Nucleus Gracilis/Cuneatus), Olives, and Medial Lemniscus.

Middle Meningeal Artery.

Cerebral Peduncles are located anteriorly/ventrally in the midbrain; Cerebellar Peduncles are located posteriorly/dorsally in the pons.