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Breaking down diabetes | Endocrine system diseases | NCLEX-RN | Khan Academy

September 10, 2019


– 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.

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