- [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.