What is hypertension | Circulatory System and Disease | NCLEX-RN | Khan Academy
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What is hypertension | Circulatory System and Disease | NCLEX-RN | Khan Academy

August 30, 2019

– [Voiceover] So let’s
just say that you go in for your annual physical exam, and you’re told that
you have hypertension. Well what does that mean, and why could this be a problem for you? Well, hypertension is another term we use to describe high blood pressure. So the pressure inside your
blood vessels is too high, or the blood that’s
moving around inside them is under a higher pressure than normal. To sort of illustrate
that let’s think about your circulatory system instead as like this plumbing system. So you’ve got a pump
that moves water around, the pump being your heart
and the water being blood, and the pumps pumping blood out to both your lungs and your body, and then receiving that blood back in. And so the pumping out
part are like your arteries going away from your heart, and then the pumping in
part are like your veins. And both these pipes, the in and the out, or your veins and your arteries, have a certain amount of pressure. So here going out we
have arterial pressure, or pressure in the arteries, and then here coming into the pump we have venous pressure. Since the arterial side is what the heart’s pumping out into, if the pressure on that side is too high it gets a lot harder for your
heart to pump more blood out. And usually this means the
heart has to do more work because it’s pumping against
higher pressures, right? Now, there are a lot of things that can make the pressure in the pipes higher, and therefore make the pump work harder, but the two main things
that we’re gonna focus on are called flow and resistance. And the flow is how we describe the movement of a volume of fluid, so how the water moves through the pipes, or in our case the blood
circulating around the body. When there’s more fluid, or flow, trying to circulate in the same space the pressure’s gonna be higher, right? Think of if you turned up
the faucet to this system, all of a sudden we’re
trying to get more water out through the same sized pipes, so now those pipes are gonna
be under a higher pressure. But how do we turn up the faucet? How do we get this increased flow, or increased blood volume
circulating around the body? Well, it’s usually because your kidneys are making you hold onto more fluid, since one of your kidney’s main jobs is to regulate the fluid in your body. It could also be because there’s more salt in your blood vessels. Fluid tends to move to
areas with more salt, so more salt in the blood vessels means more fluid in the blood vessels. And this is also why a diet high in salt can contribute to high blood pressure. Okay, so that was flow. Resistance on the other hand is like how hard it is for fluid to
move through the blood vessels. The higher the resistance,
just like the flow, the higher the blood pressure. Now, this could simply mean, just like a change in
the size of the pipes, and by size I mean diameter. So as the diameter gets smaller you have a higher resistance in the pipes, and so your blood pressure goes up. So think of like a hose that’s just open. The water sort of just falls out, right? There’s not a lot of pressure
pushing it out, is there? Well, what if you put
a small nozzle on it? All of a sudden you’ve got this serious super soaker on your hands, right? That’s because the smaller diameter nozzle is putting a lot more
pressure on the water. It’s the same with a blood
vessel that gets smaller. The blood’s going to be
under a higher pressure. Whenever your blood vessels squeeze, we call that vasoconstriction, and vaso just refers
to your blood vessels, so constricting your blood vessels. When the vessels get bigger, we call that vasodilation, because they’re dilating
and getting bigger. Now, higher resistance
could also be caused by your arteries becoming too stiff, which can happen as a result of aging or a buildup of fatty deposits. This buildup is referred
to as atherosclerosis. So you’ve got blood moving through here, and then these buildups start to happen. Or sometimes we just call it plaque, and that plaque accumulates, and in addition to making that opening that the blood can move through in the vessels smaller in diameter, it also makes the blood vessels as a whole less flexible and more stiff. Healthy arteries have a certain amount of elasticity to them, meaning they’re a little bit elastic. So maybe when more
blood moves through them they stretch just a little bit to allow that additional blood flow. If they loose that
elasticity and become stiff then they won’t stretch as much and so the resistance goes up, and also your blood pressure goes up.

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