i'm going to begin by talking about the different stages of sleep and the corresponding waveforms that you see on an eeg then i'm going to talk about the normal sleep physiology so how you know how sleep progresses throughout the night and i'll conclude the video by talking about some abnormal sleep pathology and tying those pathologies back to the different stages of sleep there'll be a couple useful mnemonics as we go and by the end of this video you'll know everything that you need to know about sleep so let's get started by talking about sleep stages and eeg waveforms i think the best way to approach this is to say what is the level of consciousness so you've got two options here you can either be awake or you can be asleep now let's start on the left side and talk about the awake conscious state when you're awake you can be two types of awake you can either be alert or you can be tired right we've all experienced this before either you're able to have conscious effort mentally in which case you're awake alert or you're really like dozing off and getting tired and wondering when am i gonna go take my nap in that case you're awake tired now if you're awake alert you're going to have beta waves on an eeg and if you're awake tired you're going to have alpha waves on the eeg now let me pause for a second and say that the reason i'm stressing what type of waves you'll see on an eeg is because for some reason this shows up all the time on usmle and comlex the test writers love to quiz you about what type of waves you will see so it's really important that you memorize these and that you understand what they look like if you want that 280 on your test so beta waves and alpha waves for alert and tired respectively now how do you remember this well there's beta waves when you're busting out work and there's alpha waves when you're about to fall asleep so remember beta waves for when you're alert and awake so you're able to give conscious mental energy this is how you feel after you have a cup of coffee and you're studying for your test and then the alpha waves when you are you know it's 3 30 4 p.m in the afternoon and you're starting to think about taking a nap what you see beneath the beta and the alpha waves is what those actually look like on an eeg it's not very important that you know what it looks like visually but if you're trying to get the perfect score on your exam then i would know it so again just to really hammer it home and say it one more time if you're alert you have beta waves because you're busting out work and if you're tired you have alpha waves because you're about to fall asleep so that's the awake consciousness now let's talk about the right side of this flow diagram right what happens when you're asleep that's really the bulk of this lecture and what you came here to learn so being asleep can be separated into two sub stages non-rem and rem sleep rem stands for rapid eye movement because as you'll see one of the hallmark symptoms of rem sleep is the fact that your eyes are oscillating back and forth now rem sleep is its own stage but non-rem sleep is further subdivided into three more stages that includes n1 n2 and n3 and the reason it's named n is for non-rem 1 non-rem 2 and non-rem 3. so each of these three stages n1 and 2 and n3 have their own eeg waveforms and i'm going to put them on the slide now the n1 stage is character categorized by theta waves and that's what theta waves look like in purple the n2 stage is categorized by both k complexes and sleep spindles and i understand that it's a little small of an eeg waveform but the sleep spindle is the really fine close together squiggly lines and the k complex is the thing that kind of looks like what you might see on an ecg it's more of an upward spike and a downward deflection so those are sleep spindles and k complexes and they're both seen in n2 or non-rem stage two and then finally in n3 you see delta waves and shown in green is what the delta wave looks like now rem i told you is its own stage and rem is categorized by beta waves right so the same waves that you see in the awake alert stage are also seen in the rem stage and because of that rem stage is called paradoxical sleep because even though you are in this very deep state of sleep it has the same eeg waveform as what it looks like when you're awake so it's paradoxical so this is the eeg waveform and an overview of your sleep stages pause the video if you want to look at this slide for a little bit more but i'm going to move on so this is what we've covered so far and now let's talk about normal sleep physiology so what i want to do is just fill in this chart i think it's the easiest way to approach this information and to allow you to form a conceptualization in your brain so here are the stages of sleep we've already talked about each of these stages and we've already talked about their eeg waveform so i'm just going to fill them in for completeness sake so that you can refer back to it as i go through the characteristics here so for awake alert and for awake tired there's really not much that you need to know so i'm just going to put n a and we'll skip those two but do memorize beta and alpha waves because that's very very important for n1 you need to know that this is the lightest stage of sleep and oftentimes you'll see sudden myoclonic jerks now i'm sure this has happened to you you've been you're laying in bed you're drifting off into sleep you've entered stage one of sleep and all of a sudden you you suddenly awake from sleep because you felt like you were falling out of your bed or you had a quick jerk in your arm or your leg and then all of a sudden it woke you up we you know it's very common most of us have experienced that and this is where it's occurring in n1 now n1 makes up about five to ten percent of total sleep time there's a little mnemonic here that i use to remember the sudden myoclonic jerks and i just rewrite the word myoclonic and i replace the ni with n1 so sudden myoclonic jerks and the spelling is exactly the same and it helps me remember that those myoclonic jerks occur in n1 stage of sleep let's move on to n2 so n2 we already talked about is is very categorized by those k complexes and sleep spindles but the other stuff that you need to know is that this is where bruxism occurs bruxism is a fancy term for teeth grinding and this is 50 of total sleep so most sleep is n2 most of the sleep throughout the night is n2 that's very very high yield to know for n3 we already talked about that you see delta waves but the other bit of information that you need to know is that this is the deepest sleep that you have and it takes up about 10 to 20 percent of the total sleep time throughout the night interestingly as you go through the through the night the length of the n3 sleep goes down so it's important physiologically to to get the n3 sleep early in the night which is why you want to give yourself plenty of time to go to bed especially when you're studying for usmle and complex let's conclude by talking about rem so rem just like awake alert shows the beta waves that's why it's called paradoxical sleep and in rem aside from the rapid eye movement which is obviously what rem stands for people are typically atonic or immobile so they're just laying there and they're really in this deep stage of sleep and their eyes are oscillating back and forth the other thing that you should know about rem sleep is that you have an increase in your autonomics so in rem sleep heart rates typically are elevated and there's classic penile tumescence and for whatever reason that shows up all the time on exams don't ask me why but it does and one of the ways that you can remember this is that rem sleep has beta waves and if you want to remember that you can remember that in addition to beta waves rem sleep has boners so the b for beta the b for boner it helps you kind of tie all that back together rem sleep takes up about 15 of your total sleep and each rem stage is in to itself minutes and that is also very good to know so at this point we've talked about the sleep stages i've told you about the eeg waveforms we went through the normal sleep physiology now let's wrap up the video by talking about the abnormal sleep or the pathologic sleep so again i think the easiest way to approach this is to just simply go through a chart fill it in and allow you to make those visual connections and conceptualize all this information for awake alert and awake tired there's no pathology there okay so we're going to skip those stages but let's begin by talking about n1 so in n1 this is affected by obstructive sleep apnea and when somebody has obstructive sleep apnea it actually increases their n1 sleep and the way that you would remember that and my mnemonic is to write obstructive sleep apnea and replace the e with the one so just like i did that for myoclonic jerks i do the same thing for obstructive sleep apnea it just you know visually i can remember it for n2 this is where bruxism occurs and i've already alluded to that and to remember this i rewrite the word bruxism with a k and two s's the k stands for k complexes and the two s's stand for sleep spindles and that allows me to connect bruxism with the eeg waveforms so that i can remember for n2 it's bruxism and i remember the eg waveform so just a nice silly little mnemonic there for n3 this is the stage where sleepwalking night terrors and bed wetting occurs and there's no mnemonic here but it kind of makes sense if you think about n3 being the deepest stage of sleep while sleepwalking night terrors and bed wetting all of those things classically happen in people that have no recollection of it happening and the reason that they have trouble remembering it is because they're in the deepest stage of sleep now it's not depicted on this slide but this is also the stage of sleep where if you get woken up out of n3 you have something called sleep inertia and this may have happened to you in the past this is when you get woken up out of sleep and even though you're awake you have all types of cognitive difficulties you don't know where you are you start saying nonsense and then maybe you go back to bed it's very common for that to happen if you get woken up out of n3 lastly for rem what you need to know is that this is affected by major depressive disorder or mdd in patients with major depressive disorder they have tons of changes to their rem sleep the ones that you should memorize are shown on the slide you have a decrease in rem latency meaning that it you go into rem faster so latency refers to the amount of time it takes for something to happen so if the amount of time it takes to get into rem goes down it means you get into rem sleep faster once you're in rem sleep there's an increased rem duration especially for the first stage of rem in the night so the first rem in the whole night in patients with depression is longer and then as the night goes it kind of shortens a bit but that first one is longer there's also an increased rem density meaning that throughout the night patients with major depressive disorder will be in rem more often and if you're looking for a way to remember what all this stuff is you know what what's happening basically in major depressive disorder the summarizing statement would be these patients don't have as many deep sleeps throughout the night because they're mostly in rem and they don't really get that really refreshing n3 stage i want to wrap up the video by talking about narcolepsy narcolepsy is a pretty unique sleep disorder and it's increasingly being tested on exams so i just wanted to spend a little bit of time talking about it narcolepsy is due to a deficiency of orexin producing neurons in the lateral hypothalamus you might see it written as orexin or you might see it written as hypocretin one they mean the same exact thing so just know that they're interchangeable you can measure orexin and you can measure hypocretin one in the csf so sometimes if a test writer is writing a question and they describe narcolepsy and they say which of the following findings would you expect to see the answer might be decreased hypocretin 1 in the cerebrospinal fluid or decreased orexin in the cerebral spinal fluid it's very high yield to know that the symptoms are pretty unique and you shouldn't miss this if they're written out in the clinical vignette sudden cataplexy and daytime sleepiness are the big two so these patients have a really tough time going to sleep at night but what happens is that they have sudden cataplexy meaning that they'll suddenly lose tone in their body and fall asleep and you've seen this probably in movies or tv shows um but it's real and it does exist and usually that cataplexy is in response to a very strong emotion so because that what i just described is so unique if you see it in a question i really hope that you you recognize that it's narcolepsy and can answer the question the treatment here is modafinil modafinil is a central nervous system stimulant and it helps people kind of stay awake during the day and not have daytime sleepiness and those sudden cataplexy events now if the person is suffering from cataplexy and if the person who's suffering from hallucinations regarding the feeling of being tired um those are called hypnagogic or hypnopompic hallucinations you can also treat this with ssris or snris those are sort of ancillary treatments that support the other symptoms but the main treatment here is going to be modafinil so i just wanted to spend a bit of time talking about narcolepsy because again it's very unique and there's a lot of different things that they can ask you that's usually not stuff that you've studied too too much but that's it for this video on sleep i hope that this was useful to you please remember that if you like the content i'm putting out to check out 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