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- Ok, so let’s sayyou have some kind of letter that you wanna, that you wanna deliver, right? So you have a letter that’s in your mailbox, and let’s say that this is thesender of the letter, right? And so the sender of that letter is gonna deliver that mail all the way over hereto the recipient, right? And the way that they’re gonnado that is you’re gonna have this mailman in this truckdeliver it from the sender to the recipient, and they’regonna drive along this road. But then let’s say something happens. Let’s say, for some reason,an earthquake happens, right? And the earthquake actuallydestroys the road over here. And so now, the mailmancan’t really get to where they need to go anymore, right? Because the road has been damaged. So why am I giving thisextremely hypothetical scenario? Well I think that it servesas a pretty good analogy towards understanding a diseasecalled Multiple Sclerosis. So Multiple Sclerosis isa disease of the brain. And more specifically, itaffects the communication within the brain. So what do I mean bycommunication in the brain? Well in the brain, you haveall these neurons, right? You have all these neuronsthat are constantly talking to each other, kinda likethese two neurons over here. And so this neuron is goingto send an electrical signal down the length of a diaxon. And that electrical signal is in the form of an action potential. And so to improve theefficiency of the communication, you have this stuff thatkind of insulates the axon, so, this stuff that I’ve drawn here in red is called myelin. And it really just makesthe action potential move down the axon much more quickly. So we can actually kind of compare this two-way communication system,right, with our mailman.
- So, you know we have kind ofthe sender of the message, that would be the first neuron, we have the message, that would be kind of like the action potential, we have the road, whichwould be, you know, the myelin and the axon together, and we have the recipient. Now, in our analogy, we had an earthquake that actually destroyed the road somehow. So, in Multiple Sclerosis,what happens is, well, you get destruction of theroad, and more specifically, you get a degradation of the myelin. And so because there’sdegradation of the myelin, we can call Multiple Sclerosisa Demyelinating Disease. So this is really where that disruption in the communication goes on, right? And when the myelin isdegraded, the action potential won’t really travel downthe axon as quickly anymore, and sometimes it may not eventravel down to begin with. So what’s causing that degradation? Well as it turns out,in Multiple Sclerosis, the immune system actuallysneaks its way into the brain, and when the immune systemsneaks its way into the brain, for some reason it mistakenlyrecognizes that myelin, right, this myelin over here, as foreign. And when it mistakenlyrecognizes it as foreign, it starts to attack themyelin, hence this degradation.
- And because the immune systemis attacking the body itself, we call Multiple Sclerosis anAutoimmune Disease as well. So that’s kind of a cellular perspective on Multiple Sclerosis, butnow I kind of want to give you a more macroscopic perspective on what the disease doesto the brain, right? So let me clear up some space over here. And let me actually show younow two different brains. So this is just really a brain scan, or two different brain scans of, well, two different brains. So on the left, we have aperfectly healthy brain. And on the right, wehave the brain of someone who’s suffering from Multiple Sclerosis. Immediately on theright brain you can tell that you have these brightspots over here, right, called Plaques.
- So Plaque is also reallyreferred to as a Lesion. And a Lesion is reallyjust a piece of tissue that’s been damaged. So let’s say, for example, you know, you have a hand over here, you know, maybe you get acut on your hand somehow. Right, you can call that cutkind of a Lesion of the skin. In Multiple Sclerosis you havea Lesion in the brain, right? And those Lesions are reallycoming from the damaged myelin from the immune system. So what happens is, youhave all these immune cells that kind of come together,right, they kind of cluster around certain parts of the brain, and they attack it. And when you have a wholebunch of immune cells coming together to attacka certain part of the body, we call this Inflammation,and because it’s happening in the brain, we callit Neuroinflammation. Now, the condition in whichyou have these Lesions, in the brain, is called Sclerosis. In the case of Multiple Sclerosis,you have multiple Lesions hence why we call it Multiple Sclerosis. Now notice how you’regetting these Lesions in different parts of the brain, ok. Different parts of the brainare gonna be responsible for different functions. Some may be responsible for Vision, others may be responsible for Cognition, for moving around, forMovement, for Touch, and so on and so forth. And depending on where theseLesions form in the brain, you can get a varietyof different symptoms that can affect all of these functions. Now, why do these Lesions form? Why does the immunesystem attack the brain? The problem is that wedon’t actually know. We’re not really sure with 100% certainty what causes Multiple Sclerosis.
- All we know is that some people may have a kind of Genetic Predisposition towards developing the disease, and that there are also probably some Environmental Factors thatmay be involved as well. And the fact of the matteris that your genetics can really interact with the environment, and that can kinda stimulatethe progression of the disease. Now the exact types ofgenes that are involved, and the exact types ofEnvironmental Factors that may be involved willbe a talk that I’ll cover in a later video, butfor now this is really all that we know about thecauses of Multiple Sclerosis. Now even though we don’treally know perfectly what causes Multiple Sclerosis, we do know who is more likely to develop the disease. So I’m gonna actually clearup some more space here again. And so now I’m gonna showyou a picture of the earth. And the reason is because I wanna give you a global perspective on,you know, the prevalence, and the incidence of Multiple Sclerosis. So the disease affects about2.5 million people worldwide. Now, is everyone on theplanet equally likely to develop the disease? Well, no. As it turns out, if you movenorth from the equator, right, so if you move north from here, you’ll notice that the incidenceof MS actually increases. And the incidence is actuallypretty high, you know, in these northern areas,right, so here in Canada, and in the northernUnited States, and here in a lot of Europe and Russia as well. So it often affects Caucasiansmore than other races. And more specificallyamong the Caucasians, it affects people of NorthernEuropean Descent more often. The disease is also more commonin women than it is in men. Right, and it’s thought thatof the 2.5 million people worldwide about twothirds of them are women. So 66% of them are women. So what age do people start to develop MS? It’s usually in the agerange of 20 to 50 years old. And it’s usually on theearlier end of that spectrum. And lastly, one thing thatI really want to emphasize is that the disease itself is NOT FATAL. So the disease itself won’tactually kill you, right, but the Life expectancy is a bit lower. And it’s thought to belowered by about, you know, a few months to a few years.
- Now even though it’s notfatal, the disease itself is quite debilitating,and it can really affect the person’s lifestylethrough a number of different signs and symptoms, and that’ll be a topic that I’ll cover in the next video.
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