Hi guys. It is Tammy with NurseMinder and today we're going to be talking
about the elements that help to create and maintain our blood pressure.
Specifically we'll be looking at the three things that influence blood
pressure and the two systems in our body that help us to maintain it. And we're
going to take care of all of that, right after this. Welcome back my name is Tammy
and this is NurseMinder and on this channel we do everything nursing so if
you're new here consider subscribing below so that you get the next video
when it's released. Have you ever wondered what's going on inside your
body that's actually regulating your blood pressure? Maybe you've gone to
those drug stores where you put your arm into the automated machine and it
squeezes really hard and seems to last forever but the readings that you get
are either always different or really really different? Well there's a few
things that are happening inside the body that are helping to regulate that
blood pressure, and we want to talk about those next. Now be sure to stay to the
end of the video because I will be talking about some of the things that
are often tested in nursing exams and things that patients often ask about. So
we'll do that after at the end. Now blood pressure is really a summary of three
things happening in the cardiovascular system. One is our heart rate which is
measured per minute. The second is our stroke volume and that's how much blood
is squeezed out of the heart with every contraction . And the third is peripheral
resistance and this is those arteries that the blood is being pumped into - how
willing are they to accept that blood and how much are they resistant. So if
I were to give an analogy, for example it's really windy today, this would be
considered how many steps I take in a minute under normal conditions, stroke
volume is the distance between my steps - so how far I am covering, and then that
resistance would be, today's really windy it's super windy, and so I have to work
much harder to get the same distance. That would be a good analogy to share
with your patients. Now in terms of heart rate, there's many things that can
impact heart rate and it is driven in particular by two nerves in the heart -
and that is the vagal nerve and the accelerator nerve. The vagal nerve is
what slows the heart rate down so when you go to sleep or when you're like oh
bear down, holding your breath, it will slow the heart rate. And the accelerator
nerve is what increases it. So these two work in tandem but there's a host of
things that can impact our heart rate which will change our cardiac output and
will influence our blood pressure. Now I just have a small list here, this is not
exhaustive, but activity as we know exercise increases the heart rate.
Hydration. If you're dehydrated in particular then our heart rate will
increase to supplement that movement of fluid. Our oxygenation status- if we are
deficient in oxygen again the heart rate will increase to impact our cardiac
output. If you are under stress- increased heart rate. Our thyroid, we can that hyper or hypo
thyroid and so there's some other medical conditions that will influence the
functioning of the heart rate - illnesses and medications. So you can see there's a
variety of things that can influence just this one factor. Factors that affect
stroke volume included how much fluid is coming into the ventricle. So we call
this preload. And then there is the heart's ability to actually contract strong
enough to eject that fluid out, so potentially you may be heard people who
have have heart failure or increased heart size those are things that would
affect stroke volume. So ventricular hypertrophy would be an example. And then
factors that influence peripheral resistance. So this is the after load. This
is the pressure that the heart needs to generate in order to pump that blood out.
So I am going to write after load.
But this would be the vessel size and how willing it is to accept it, so how
compliant is it and again there's a whole host of diseases that can create
compliance issues so athero, atherosclerosis is a common one. That's
plaque in your vessels that will make those vessels more rigid that they don't
have that stretch capacity to take fluid into it. And so here we have a variety of
things can affect these three main elements of blood pressure .Now of course
some of this peripheral resistance can be affected by some of the things that
affecting heart rate so if I'm under stress, I've got that sympathetic nervous
system fight or flight going, my vessels constrict and it will influence the
resistance at which the heart is pumping against. Okay so now let's talk about
what a blood pressure reading is. So it's measuring that pressure inside the
system as a result of heart rate stroke volume and resistance and we end up with
what's call the systolic number and a diastolic number. Now you notice that the
systolic vessel is wider than my diastolic and that's for a very
important reason. Imagine you're hooked up to a water hose and we turn on the
tap. All that pressure is coming through and so this is really my water hose here
and it's turned on and we have maximum pressure in here. So if you were to go
and step on that garden hose you wouldn't be able to really manipulate it
because it's full and it's tense. Well when you turn the top off, the pressure
goes down but it doesn't eliminate the water that stays in the hose or in the
vessel, there's still some water there and this would be our diastolic pressure.
So systolic is the amount of pressure in the vessel when it is in contraction and
diastolic is when the vessel is relaxed. You'll hear a lot about these numbers
120 over 80. Now we know there's been a lot of changes recently with the
guidelines for high blood pressure but typically 120 and less is considered
normal for systolic and 80 or less is normal for diastolic . So you can see here
that the normal blood pressure is now considered to be less than 120 over 80.
There's my systolic and my diastolic. And elevated blood pressures now between the
readings of 120 and 129. Hypertension is when we now see a reading of 130 to 139
and we're starting to see changes in our diastolic so eighty to eighty nine
milligrams of mercury. Stage two hypertension is anything greater than
140 over 90 diastolic or higher. Okay now the other two systems that are
working in our body to help us maintain our blood pressure are what's known as
baroreceptors and the renin-angiotensin-aldosterone system. Now
I will talk about this in another video but just to give you an overview of these
two systems. The baroreceptors are measuring pressure, so the stretch that
exists in those vessels ,and in particular there's two places. One is
just off the heart as it's leaving, as the blood is leaving the ventricle to go
to the body we have a baroreceptor. And the other is off the carotid
arteries as its heading towards the brain because the brain likes to be
perfused. This one, okay so coming back baroreceptors, are looking for pressure
and that will affect the vessel size and heart rate.
The RAAS system- the renin-angiotensin-aldosterone system
will be also assessing for pressure but it's going to be focused on maintaining
water and sodium in the system should our blood pressure go low, and getting
rid of it should our blood pressure be too high. So there's a quick summary of
the elements and systems in place already in our body to help us regulate
our blood pressure. Okay as promised I mentioned at the end of this video I
would talk about what is often tested for students and nursing exams and what
patients often ask about. And to summarize it - its cardiac output! You're
going to want to remember the factors that affect cardiac output. So heart rate x
stroke volume and that blood pressure is also with - also has the
element of peripheral resistance. So when you put those things together, any
question you have that is looking at the patient's cardiovascular system will
be looking for those elements. Patients will also ask about cardiac output, but
they don't phrase it that way. They'll ask you what is blood pressure and so
I've given you the hose analogy so that when you need to explain what systolic
and diastolic is and what a normal blood pressure would be, you have that prepared.
The second NCLEX thing that we tested on is the hypertension treatment scale. So
you want to be making sure you recognize what is elevated blood pressure, what is
considered to be hypertension stage 1, stage 2, and what would be normal. Now be
sure to watch the next video on the renin-angiotensin-aldosterone system and
the baroreceptors so you get a little bit more insight
into how they're really working behind the scenes to make sure our blood
pressure stays in that safe range so our body is perfused well with hydration and
nutrition. And until next time guys, make it a great day :)