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What are dementia and Alzheimer's

Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Tanner Marshall.

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Video transcript

- [Voiceover] Let's say you're going to the grocery store, but you realize you left your keys in your room. You go up to get them and then walk into the room and look around for a second, and realize you completely forgot why you even came here in the first place. We all know how frustrating this can be, right? But this scenario is totally normal and is something everybody experiences from time to time. And besides causing you to take one more trip up the stairs to your room after you remember again, it doesn't throw off your day too much. When problems remembering or problems with your thinking skills in general become so severe and so common that they actually interfere with your daily life, it might be diagnosed as dementia. Dementia, though, is not a specific disease. What do I mean by that? Well, it's more of a general term that describes a range of potential difficulties with reasoning, judgement, and memory. For example somebody with dementia might have troubles with speaking or writing coherently, or understanding what was spoken or written. They also might have trouble recognizing their surroundings, especially when those surroundings should normally be very familiar to them. Planning and performing tasks that require multiple steps can also be difficult for patients with dementia. Even tasks that you might think are really simple, like getting dressed and eating, these can become a serious challenge for patients with later-stage dementia. And to make matters worse, many times, patients aren't even aware that they're experiencing any troubles or any sort of cognitive deficiencies at all. Now, dementia is most common in the elderly, especially after age 65. But it is certainly not a normal part of aging. So, dementia, in very general terms, is something we use to describe when someone has troubles learning, remembering, and communicating. But where does Alzheimer's Disease fit into this? Well, Alzheimer's Disease is a type of dementia. Specifically, it's what's known as a neuro degenerative disease, and it counts for about 60 to 80% of all cases of dementia, affecting about five million people. So, if we look at "neuro," we know that this refers to the nerves of the nervous system, or basically your brain, and then, "degenerative" or "degeneration" means to decline or to deteriorate. So, with Alzheimer's Disease, there's this deterioration of your nerve cells in your brain. And this brain of yours houses about a hundred billion nerve cells, which are also called neurons. And these guys communicate using a hundred trillion connections. That's a lot. Now, this communication and those connections are what control essentially every other organ and every other function in your body, not to mention your thinking abilities. Unfortunately, though, the main type of cells that Alzheimer's Disease targets and affects are these precious neurons. And depending on where the affected neurons live in your brain, different functions of your brain can be affected. For example, if nerve cells in this area of your cerebrum are affected, you might have trouble solving problems or making plans, because these cells help you do those things. Or, if the neurons in this area are affected, you might have problems remembering something or storing new memories. And as Alzheimer's Disease progresses, more and more of these neurons die, and your brain tissue actually begins to shrink due to this loss of nerve cells. All right. So, nerve cells in your brain are destroyed in Alzheimer's Disease, but how are they destroyed? Well, unfortunately, answers to seemingly fundamental questions like these aren't really fully understood yet. But scientists have pinpointed a couple of possible culprits that usually seem to be involved, and these are called plaques and tangles. Plaques are like these weird, abnormal clusters of protein fragments that build up between neighboring neurons. So, this is a normal group of nerve cells going about their business, you know, communicating and what-not. With Alzheimer's Disease, these plaques start to form in between these neurons, which is thought to make it a lot harder for them to communicate. Now, besides plaques, the other hallmark of Alzheimer's Disease are called tangles. Unlike plaques, though, these guys are found inside the neurons, and most of these are made up of a protein called tau. And tau proteins are helpful usually, but in Alzheimer's Disease, they're all twisted and abnormal, which ultimately ends up hurting the cells. Okay. But we still haven't said why these plaques and tangles form. Well, again, that question is still a huge, huge area of research, and is something scientists continue to gain insight on but have yet to completely understand.