If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Breaking down 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.

Want to join the conversation?

Video transcript

- Diabetes mellitus is a syndrome that's caused by improper function of insulin, and, as a result, there's disregulation of the blood sugar levels. This results in high blood sugar, which is also known as hyperglycemia, but what exactly does this all mean? To get a better idea, let's first go over the body's normal regulation of blood sugar. To do that, I'm gonna just bring in a diagram here. In this diagram, you'll see up here, you have the esophagus, that goes into the stomach and into the beginning portion of the intestines. Then, here in pink, represents a blood vessel. In yellow here, is the pancreas. There are three major types of nutrients that your body uses for energy. There's fat, protein, and carbohydrates. We're gonna be focusing on carbohydrates. I'm gonna just abbreviate that CHO, which stands for carbon, hydrogen, and oxygen, which is the chemical makeup of carbohydrates. The carbohydrates that we eat go through our esophagus and into our stomach and they start to get digested. As they enter into the intestines, they're digested down into glucose. Glucose is a simple sugar, and it's very important in the body because cells throughout the body use glucose as energy. Glucose, like I said, is a type of sugar, so, sometimes, people will refer to it as blood sugar levels, and what they are referring to are the level of glucose in the blood. This glucose is absorbed through the GI tract into the blood vessels here. Once it's in the blood, it then travels to the cells of the body, such as muscle cells, where it can be used for energy, or the glucose in the blood can travel to the liver, where it is stored to be used as energy in the future, so let's see this happen. This is where the role of the pancreas becomes important because glucose, on its own, is not able to actually enter the cells, like muscle cells, or into the liver. Without the pancreas, glucose would just become piled up in the blood. Luckily, the pancreas here can sense this pileup, or this increase in the blood sugar, and it releases a hormone known as insulin. When the pancreas releases this insulin, it kinda acts like a key that unlocks the cells of the body, such as the muscle cells and the liver, allowing the glucose to enter the cells, so, in the case of the muscle cells, those cells can now start to do work. In the case of the liver, the glucose can be stored. However, if this just kept going and insulin wasn't kept in check, what would happen, over time, and as you can see here, is that that blood glucose level would get too low. Fortunately, the pancreas can also sense when these blood glucose levels are getting too low and it stops secreting insulin, and it starts to secrete another hormone, known as glucagon. What glucagon does is it stimulates the liver to release this stored glucose back into the blood to replenish the blood glucose levels, and, eventually, the blood glucose levels return to normal. Let me draw a diagram here to help you remember how our bodies maintain the blood glucose levels. You can think of the maintenance of the blood glucose level as being a balance between insulin, and if the balance is tipped in the direction of insulin here, it will result in the unlocking of cells. It will also allow the liver to store the glucose, then both of these things result in a lowering of the blood glucose level. Then, as this gets too far, the pancreas reacts, and it then has glucagon to shift the balance, by causing the release of that stored glucose, which results in a raising of the blood glucose level. Now that we have an understanding of how the body normally regulates blood glucose levels with insulin and glucagon, what exactly is going on in diabetes mellitus? Well, I mentioned at the beginning that diabetes mellitus is a syndrome that's caused by improper functioning of insulin, and in a sense, the insulin just doesn't work. This may be due to many different underlying causes, such as the pancreas here not being able to produce the insulin, the pancreas just may be producing too little insulin, or, for some reason, the cells may not be receptive to the insulin, in a sense that that key mechanism doesn't unlock the cells to allow the glucose to get in. Regardless of the underlying mechanism, though, when you don't have insulin here to balance out the blood glucose levels, this balance is gonna be tipped in the favor of glucagon. As such, what's gonna happen is these effects of glucagon here, are going to become more predominant, so what you see in diabetes mellitus, one of the characteristic findings is that there's going to be hyperglycemia. This is because the glucagon is causing the glucose from the liver to be released, and since insulin isn't functioning properly, this key effect here, also isn't working, so the cells aren't able to get all of this glucose that is in the blood, so despite having all of this energy present in the blood, the cells aren't able to use it, so someone with diabetes is, oftentimes, very fatigued or tired. That's because they're not able to extract the energy from the blood. Lastly, the body tries to compensate for this increased concentration of glucose here in the blood, and what it tries to do is it tries to dilute the blood with water from cells. What happens is that all this water leaves the cells, and the person becomes dehydrated, so, frequently, someone with diabetes will be dehydrated and very thirsty. Diabetes mellitus is a syndrome that's caused by dysfunctional insulin or a lack of insulin, resulting in an inability of the body to maintain its normal blood sugar balance, and you get this hyperglycemia here. Then, over time, actually, this persistent hyperglycemia can actually cause damage to many vital organs in the body, such as the nerves, eyes, and kidneys.