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Blood Pressure Values
Why Does
Blood Pressure Have Two Values?
Ashish
You have probably heard a great deal about the heart and blood
pressure and the unbreakable bond they share with each other.
Separating blood pressure from the heart is about as easy
as uprooting an oak tree with your bare hands.
However, when talking about blood pressure, there are two
values you must consider. Have you ever thought about why there are two values
when measuring blood pressure?
Pressure is a regular physical quantity, right? Like any other
physical quantity, logic would suggest that it should also have one value and
respect the laws of nature, correct?
So why is blood pressure always expressed through two values,
rather than one?
Blood Pressure
Without getting too scientific about it, blood pressure (BP) is
the pressure that flowing blood exerts on the walls of blood vessels.
Since blood is sent and received by the heart (which sits slightly
off-center, towards the left side of the chest), it does so with the help of
blood vessels, such as veins and arteries.
Blood pressure varies from one individual to another according to
their age, physical and mental health, and disease status.
This pressure is regulated by the nervous system and the endocrine
system of the body, but can also be impacted by the physical qualities of your
heart and circulatory system.
Blood pressure is usually measured by a sphygmomanometer on a
person’s upper arm. The ideal range of blood pressure is 120/80 mm Hg.
As you can see, BP is expressed in two values: 120 and 80. But
why do we need two numbers?
Why the Double Measurement?
The two readings of BP represent two pressure readings; systolic
pressure (the higher of the two readings, usually expressed before the
other reading) and diastolic pressure.
Now you may ask: why are there two kinds of pressure involved with
a single organ system? Well, allow me to explain.
Systolic and Diastolic Pressure
A complete cardiac cycle includes two parts: a systole and
a diastole.
The heart contracts and lets blood out through its chambers to the
blood vessels; this action is called a systole, so the pressure exerted on the
walls of the blood vessels during this period is called systolic pressure.
On the other hand, when the heart relaxes and allows its chambers
to fill up with used blood, it’s called diastole, so the pressure exerted upon
the walls at that time is called diastolic pressure.
Consider it like this; systolic pressure represents the maximum
pressure that is exerted upon the walls of arteries, while diastolic pressure
represents the minimum pressure that is exerted upon the walls of arteries.
Therefore, the two values of BP that you see are actually the
values of the systolic and diastolic pressure, respectively.
For adults, the ideal range of systolic pressure is 90-120 mm Hg,
and for diastolic pressure, it is 60 – 80 mm Hg.
Hypertension and Hypotension
The condition of abnormally high values or low values of blood
pressure is referred to as hypertension and hypotension, respectively.
Needless to say, both of these conditions are harmful to the human
body.
To maintain a healthy blood pressure, you must follow a diet that
is not particularly high in saturated fat and sodium content (excess salt leads
to hypertension).
You should also keep a close watch on your weight, but most
importantly, get off the couch and get some exercise into your life!
Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spends a lot of time watching movies, and an awful lot more time discussing them. He likes Harry Potter and the Avengers, and obsesses over how thoroughly Science dictates every aspect of life… in this universe, at least.
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