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Pathophysiology - Type I diabetes

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 Matthew McPheeters.

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  • aqualine ultimate style avatar for user Physio Crisis
    You mention a lack of insulin blocks the uptake of glucose by the brain, but I was under the impression thatr the brain is free from a reliance on insulin.
    (4 votes)
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    • female robot grace style avatar for user Anna
      The brain and liver don't need insulin because they don't have the insulin mediated GLUT4 protein to transport glucose but rather a non insulin mediated glucose transporter.

      So if someone has high blood sugar the liver will store it and the brain will use it and so hyperglycemia does not mean diabetes unless it spiked so high that it has become long term.

      This is why some people have prediabetes which is reversable when they have high blood sugar and some don't even have prediabetes but instead they are very active and don't have much fat in their bodies so they need that high blood sugar for their muscles.
      (11 votes)
  • male robot hal style avatar for user Rohan
    what is genetic predisposition ?
    (2 votes)
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  • starky seedling style avatar for user Ivana Djordjevic
    I came across an article that says that T-cells are the one that damage the pancreas, and that the antibodies have little influence in pathophysiology of diabetes and are more important for diagnosing the disease. So, is it true, or they kind of work together? Cause you mentioned both, but in the video it seems like the antibodies have more influence.
    (4 votes)
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    • leafers ultimate style avatar for user tartan.handbag
      i was also wondering about this. i read that type 1 diabetes melitus (T1DM) is a type IV hypersensitivity autoimmune disorder, meaning it is T-cell regulated, specifically by CD8+ cytotoxic T-cells, so as to the antibodies, i couldn't say. i would also like some clarification.
      (1 vote)
  • duskpin seed style avatar for user SweetCake367
    What color is the pancreas?
    (2 votes)
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  • starky sapling style avatar for user elizabeth
    I've heard that having dark lines on the back of your neck is a sign that you have a higher risk of diabetes. Is this true?
    (1 vote)
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  • duskpin ultimate style avatar for user BarbaraDavis04
    What happens if you don't glucagon.
    (1 vote)
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    • leaf green style avatar for user Joanne
      If the pancreas does not make and release glucagon, then blood sugar declines. If blood sugar goes too low, a person dies. It is rare to have this problem. Normally, insulin responds if blood sugar gets too high and allows glucose into cell, thus lowering blood sugar. Glucagon responds if blood sugar gets too low and causes the stored sugar to be released into the blood, thus raising blood sugar. Type 1 diabetes is much more common, where there is a lack of insulin so blood sugar goes up.
      http://www.yourhormones.info/hormones/glucagon.aspx
      (2 votes)
  • aqualine ultimate style avatar for user NHill1067
    Seeing how glucose takes up a great amount of room in the blood stream, do organs and muscles not get enough oxygen from red blood cells?
    (1 vote)
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    • female robot grace style avatar for user Fire Bird
      Having too much sugar(glucose) in your blood is like having too much rain in a small pond—the flooding can cause damage for everything around it. Too much blood sugar can trigger a chemical process in your red blood cells, which transport oxygen in your bloodstream, that causes your red blood cells to want to hold onto oxygen more tightly. That keeps oxygen from getting to your tissues. When that happens, the glucose attaches to whatever it can find, most likely proteins in your blood and tissues. These proteins deposit in tissues, which leads to the development of cataracts, joint abnormalities, and lung problems.
      Hope this helps!
      (2 votes)
  • blobby green style avatar for user Mireya.Ervin
    Hello;
    Thank you for such a great lecture on DMI. When you state: "If insulin was acting on its own...." What do you mean exactly? Without being secreted by the Beta cells? If so, how does it happen?
    (1 vote)
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    • leaf green style avatar for user Joanne
      At in the transcript he says "if insulin was acting on its own the blood glucose level would get too low, And luckily, the pancreas senses that too and secretes glucagon." He is just explaining that there are two hormones that respond to changes in blood glucose. He was actually not saying insulin acts on its own, he was saying it is a good thing that it doesn't act on its own and glucagon is there too. So, I think you have picked up on a statement and thought he was saying this is true. But he was actually saying it is not true. He is going too fast in his comments. Sometimes reading the transcript helps make the words clearer. To recap: Insulin is released when we eat sugar or carbohydrates. After eating, when we have hyperglycemia, insulin is released. Insulin is the hormone that allows glucose to get into the cells from the blood so blood glucose goes back down to normal. When we are asleep, our blood glucose declines. The pancreas secretes glucagon when we have hypoglycemia. The glucagon causes the break down of a carbohydrate we store in the liver, glycogen. Glycogen breaks down into molecules of glucose returning the level in the blood back up to normal. Both of the hormones are released by the pancreas. I hope this helps.
      (1 vote)
  • blobby green style avatar for user Rubeysa Şengün
    Does insulin regulate the release of glucose from fat tissue? Because you mentioned something like that at second. Wihout insulin the tissues cant take the glucose drom blood but the adipose tissue store it. What does mean?
    (1 vote)
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  • leafers tree style avatar for user absnt-mndd
    Kind of a random question, but does anyone know of a disease where the alpha cells are destroyed by some autoimmune response and the body can no longer produce glucagon? So like DMT1 but opposite? I know it's random, but just curious.
    (1 vote)
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Video transcript

- Now Diabetes Mellitus is a group of disorders that's caused by improper function of insulin which is a hormone responsible for regulating blood sugar or blood glucose. And this results in Hyperglycemia. But since Diabetes is a group of disorders there's many different underlying pathophysiological mechanisms that can cause the disease. And depending on which mechanism is occurring in someone the presentation of the disease can actually be very different. So before we get started, I want to briefly talk about the Pancreas. Now you can see here we have the esophagus coming down and it dives behind the liver here. And then it goes into the stomach and then the stomach goes back behind the liver and comes out as the small intestine. And in yellow here, nestled in next to the small intestine and behind the stomach is the Pancreas. Now, the Pancreas is frequently referred to as being comma shaped and you can kind of get that. Oh, if you kind of turned it on its side it might look like a comma. But the way I like to remember how the Pancreas looks is by thinking about my favorite professional football team which is the Minnesota Vikings. And I kind of think the Pancreas maybe it looks like the horns on the side of the Minnesota Vikings helmet. So whatever helps you remember what the Pancreas looks like. But regardless, the Pancreas has two main functions. And the first function is Exocrine. What this means is that the Pancreas secretes Enzymes into the digestive tract which then chemically digests food and help your body absorb the nutrients we eat. So it helps with digestion. But the Pancreas also has some Endocrine function. And what this means is that it produces Hormones. And specifically for the Pancreas these Hormones help the body with Metabolism. But what does all this have to do with Diabetes? Well, I mentioned earlier that Diabetes Mellitus is caused by dysfunction of insulin which is one of these Hormones that the Pancreas produces. And in Type 1 Diabetes, certain areas of the Endocrine portion of the Pancreas are destroyed so that the Pancreas cannot produce insulin. And Type 1 Diabetes is actually a relatively uncommon disease. It affects about three out of every 1,000 people in the United States. Now, let's dive a little bit closer into the Pancreas to get a better understanding of what's going on. So the cells that are responsible for the Endocrine function of the Pancreas are located in regions of the Pancreas that are known as the Islets of Langerhans. So let's just draw those in here. So in these Islets of Langerhans there are two main cell types types that are responsible for producing Hormones. So in blue here, we have the Alpha cells. And the Alpha cells are responsible for secreting glucagon. Then in green we have the Beta cells. And they're responsible for secreting insulin. And as I've mentioned before, these two Hormones are responsible for regulating much of the bodies metabolism. And one specific component of this is our Blood glucose or our Blood sugar level. So what happens is if someone, just say, you pretend you just had a meal and your body starts absorbing the sugar from that meal. What's going to happen is your Blood sugar levels or your Blood glucose levels are going to increase. And this increase in Blood sugar is sensed by the Beta cells in the Pancreas and they'll secrete insulin into the blood. And what it does is that insulin is then going to lower the Blood glucose level by causing the cells all over the body to take up and absorb the glucose so that they can then use it for energy. Or it could be stored in the liver. And either way, the glucose comes out of blood so the Blood sugar level lowers. Now if insulin where to act on its own, the Blood sugar level or Blood glucose level would get too low. It would start to decrease from its normal level. And luckily the Pancreas senses this too in the Alpha cells or the blue cells here and secretes glucagon. And what happens then is glucagon causes the Blood glucose level to raise, going back to normal. And it does this by causing the liver to release the glucose that's stored there. So what does this all have to do with Diabetes or specifically Type 1 Diabetes? Well, in Type 1 Diabetes there is destruction of these Beta cells in the Pancreas so the body can't produce the insulin. And if the body can't produce insulin it's not able to lower its Blood glucose level and you have an unbalanced glucagon response. Which results in this raising of the Blood sugar and this is known as Hyperglycemia. Hyper for high, glycemia for blood sugar. But what is the underlying cause of this destruction of the Beta cells? I'm going to just slide this over so we can get a little more room to work on it. Well, Type 1 Diabetes is an Autoimmune disease. And as you can imagine by the name it has something to do with the immune system. And what happens is that someone who develops Type 1 Diabetes was born with a genetic predisposition to the disease. Now, this doesn't necessarily mean that he or she had the disease at birth. But they just had something in their genes causing them to be more likely to develop Type 1 Diabetes. Then over time there was some sort of Environmental trigger. And this part of the disease process isn't quite as well understood. And it could be something potentially like a virus, or some sort of toxin, or something else. But regardless, there's some sort of trigger that causes someone with a genetic predisposition to have this Autoimmune response or production of antibodies and T cells that then attack the Beta cells. And this is what causes the destruction of the Beta cells in the absence of the production of insulin. Which is the underlying cause of Type 1 Diabetes. And it's this Autoimmune attack of the Beta cells here that causes the Pancreas to not be able to produce any insulin. And when it can't produce any insulin what happens is that the individual will develop Type 1 Diabetes. Well, let me just move over again so we can get a little more space to go through why symptoms develop in Type 1 Diabetes. All right, so imagine a blood vessel here. And this blood vessel is transporting glucose. And in a normal individual without Diabetes this glucose is going to go to lots of different organs in the body. Such as the brain, and the muscles, and maybe give them a little Popeye tattoo for good measure. As well as the liver, where that glucose can be stored. But unfortunately in Type 1 Diabetes the insulin isn't present to take the glucose out of the blood and help it get to these organs. It gets blocked, almost like the body is starving despite having all of this glucose. And so what happens is that the liver acts like it is starving and it releases its stored glucose back into the blood. And then just like the glucose can't get out of the blood to some of these organs, it also can't get out and be stored in the fat or the adipose tissue, which I'll draw here. And so what the fat does is to also kind of try and help the body create more energy is it breaks down into something known as free fatty acids. Which I'll just abbreviate FFA, which the body can then also use for energy. It's this process here that results in the symptoms of Type 1 Diabetes. And the first one is what I'll call "Starvation in the face of Plenty." And by this I mean, the body almost acts like it's starving even though it has all of this glucose present in the blood. And this results in symptoms like lethargy and fatigue. Because it's trying to maintain the little glucose it thinks it has for the brain and the other organs that are vital and really need it. So someone with Diabetes will be lethargic and fatigued. And then the next thing that happens is, occurs in the kidneys. Now normally the kidneys reabsorb all of the glucose that's in the blood and put it back in the blood when it's, when they're filtering the blood. But when this glucose level gets so high from Diabetes it overwhelms the kidneys. And that glucose spills out in the urine. And this is known as glucosuria or glucose in the urine. And glucose is an osmotically active soluble. What does that mean? Well, what it means is that it tends to draw water with it. So as the body pees out all of this glucose a lot of water comes with it. And this is known as polyuria or poly for kind of lots or many and uria for urine. And this results in dehydration because you're losing all the water and thirst. So, someone with Type 1 Diabetes is frequently going to present with being tired and fatigued, going to the bathroom a lot and dehydrated. And unfortunately, for some individuals, if they get sick when they have Type 1 Diabetes before it's been diagnosed, the body can't compensate for the stress and you can get a life threatening disease that's called Diabetic ketoacidosis or DKA which is a life threatening form of dehydration and acidosis. When it comes to diagnosis about 70% of individuals with Type 1 Diabetes will be diagnosed in this stage before it gets too bad. Bit unfortunately, about 30% of individuals who are diagnosed with Type 1 Diabetes actually have Diabetic ketoacidosis or DKA, as their presenting symptom. So this is just a brief overview of Type 1 Diabetes which is an Autoimmune disease. Meaning that there's antibodies and T cells that destroy the Beta cells of the Pancreas so that the Pancreas can't produce insulin, resulting in Hyperglycemia or high blood sugar. And it's this high blood sugar that results in all of the symptoms of Type 1 Diabetes.