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Video transcript

- [Voiceover] All right, so it's really important to keep your blood pressure under control. If it's not under control and you let it get too high, this extra pressure that's not supposed to be there starts to damage the whole plumbing system. Higher pressures can both damage the pump, which is your heart, and the pipes, which are like your arteries and your veins. And if these two supply systems become damaged, the organs they supply can also be damaged, which is not good. So let's think about this, you've got this arterial pressure coming out of the pump, and then this venous pressure coming into the pump, right? Well what happens on the arterial side? Well the heart pumps blood out. Since there's this pressure though, the heart has to basically pump hard enough to generate its own opposing pressure that overcomes this arterial pressure in order to actually get this blood moving around our system. So let's remember that the two factors that affect pressure in the blood vessels are flow, which is related to the volume of blood circulating around the body, and then the resistance, which makes it more difficult for blood to move around. So increasing either flow or resistance also increases our pressure, right? Well, there's actually an equation that relates these three guys, and that's the following. So you have your pressure out, which is the same as our arterial pressure, minus the pressure in, which is like our venous pressure, and is usually way lower than the arterial pressure. And that is equal to the flow times the resistance. So let's map these guys out. As we move from pressure out from the arteries to pressure in from the veins, we're gonna run into some resistances. We have some resistance, R, from the arteries, and then a lot more from the arterials, which are like these smaller branches of the arteries. And remember when the pipes get smaller, our resistance actually goes up, right? And then finally, after those arterials, we get to the capillaries, which are like the smallest, tiny little pipes that give blood to your tissues. After the capillaries, they get bigger, and then come back to your heart through your veins. Until finally you get a little more resistance from your veins, but not much. So that's the resistance, but let's not forget to also add this flow of blood circulating around, which is a certain volume of blood moving per minute, which is our flow. So from the equation if you increase the flow, you increase the pressure, or if you increase the resistances, say your arteries get narrower, you also increase the pressure. So anything that increases our pressure on the arterial side is gonna make our heart have to pump harder, right, since it has to overcome this increased arterial pressure. So if this pressure goes up, what do we do? Well, let's think about that, what's one way we could pump harder through our plumbing system? Well, we can try to invest in a bigger pump, right? Well, that's not too far off, actually, because what happens when your heart needs to pump harder is that its muscles actually get bigger, which is called hypertrophy. And at first you might think, hey, that doesn't sound so bad, it's like when I go to the gym and bulk up my biceps. And it kind of is, so much so that it changes shape just like your biceps, but when your heart changes shape and hypertrophies, it actually ends up pumping less effectively, so it's a less efficient pump. If we take a look at all the chambers of your heart, you've got the right atrium up top right, which lets blood down into the right ventricle and then the left atrium up top left, which goes down into the left ventricle. And it's this left ventricle that does the pumping out to the body, so it's this guy that usually tries to bulk up and gain muscle to beat out that arterial pressure. Not only does this extra muscle cause the heart to pump less effectively, as you can sort of see, there's also less room in the chamber to fill with blood. So now there's even less blood being pumped out with each beat, and so less blood is delivered to the body and the organs. So as both the filling volume and the pumping ability decreases, our bigger and bulkier pump isn't going to do as good of a job in giving our body blood, right? And when this happens, it can be considered this early manifestation of heart failure, which as we've seen is a result of a higher arterial blood pressure.