On screen facing out is a young man's head and upper torso.
The force of blood on artery walls is called blood pressure.
Normal pressure is important for the proper flow of blood
from the heart to the body's organs and tissues.
An overlay in the middle of the man's chest
shows the heart with its main arteries and veins.
Each heart beat forces blood to the rest of the body.
A cutaway shows a close up of the heart and blood vessels between the lungs.
Near the heart, pressure is higher, and away from it lower.
Another cutaway shows a close up on a small segment of artery,
which pulses as blood is pumped through.
Blood pressure depends on many things, including
how much blood the heart is pumping
and the diameter of the arteries the blood is moving through.
Generally, the more blood that's pumped and the narrower the artery
the higher the pressure is.
The image goes back to the man's upper body with the heart overlay.
A blood pressure cuff around his upper arm is connected
to a digital meter on the wall.
Blood pressure is measured both as the heart contracts,
which is called systole, and as it relaxes, which is called diastole.
Systolic blood pressure is measured when the heart ventricles contract.
Diastolic blood pressure is measured when the heart ventricles relax.
The heart in the overlay beats and the numbers
on the meter change as the narrator talks.
A systolic pressure of 115 millimeters of mercury is considered normal,
as is a diastolic pressure of 70.
Commonly, this pressure would be stated as 115 over 70.
Stressful situations can temporarily cause blood pressure to rise.
If a person has a consistent blood pressure reading of 140 over 90,
he would be evaluated for high blood pressure.
Left untreated, high blood pressure can damage important organs,
such as the brain and kidneys, as well as lead to a stroke.