High blood pressure, or hypertension
is a common condition in which the force of blood
on the walls of your arteries is often too high.
Arteries are the blood vessels that carry blood away from your heart
to supply your tissues with oxygen and nutrients.
In your heart, two chambers, called ventricles,
contract with each heartbeat to push blood to your lungs
and through your arteries to your body.
As blood flows through them, three main factors
affect the pressure on your artery walls.
The first is cardiac output,
or the amount of blood your ventricles push out of your heart each minute.
Your blood pressure goes up as cardiac output increases.
The second factor affecting your blood pressure is blood volume,
or the total amount of blood in your body.
Blood pressure also goes up as blood volume increases.
The third factor that affects your blood pressure is resistance,
which is anything working against the blood flow through your arteries.
Several factors contribute to resistance.
One resistance factor is the flexibility of your artery wall.
Healthy arteries expand with each heartbeat
to help reduce blood pressure on the wall.
Another resistance factor is the diameter of your arteries.
Your body is able to increase the diameter of your arteries
to lower your blood pressure,
or reduce the diameter to raise your blood pressure.
A third resistance factor is blood viscosity, or thickness.
In your blood, more particles, such as proteins and fat, increase viscosity.
If your blood is thicker, your blood pressure goes up
as your heart works harder to push it through your arteries.
Your blood pressure can be measured with a device
called a sphygmomanometer, or blood pressure cuff.
When your heart beats,
the pressure of blood on the walls of your arteries
is called systolic pressure.
When your heart relaxes between beats,
pressure on the artery wall is called diastolic pressure.
While your blood pressure may change throughout the day,
it should normally be less than 120 millimeters of mercury for systolic pressure,
and less than 80 millimeters of mercury for diastolic pressure.
If your systolic pressure frequently stays above 140,
or your diastolic pressure frequently stays above 90,
you have high blood pressure.
Over time, high blood pressure will damage the walls of your arteries.
Your artery wall may become weak
and form an enlargement called an aneurysm.
Or the wall may burst
and bleed into the surrounding tissue.
Small tears in your artery wall may attract certain substances in your blood,
such as cholesterol, fat, and calcium,
to form a build-up called a plaque.
Blood flow through your artery decreases as the plaque enlarges.
Blood cells can stick to the plaque and form solid clumps, called clots,
further reducing, or completely blocking, your blood flow.
Damage to your arteries raises your blood pressure even more
by making your heart beat more forcefully.
Artery damage and reduced blood flow lead to conditions such as:
a stroke,
heart attack,
or kidney disease.
In most cases, the cause of high blood pressure, or hypertension, is unknown.
This type of high blood pressure is called primary, or essential, hypertension.
Treatment for essential hypertension includes lifestyle changes,
such as eating a healthy diet.
If you are sensitive to the sodium in salt, your doctor may recommend limiting your intake
of salt and highly processed foods.
Sodium may cause your body to retain water,
which increases both your blood volume and your blood pressure.
Other lifestyle changes that can reduce blood pressure include avoiding excessive alcohol intake;
getting regular exercise;
losing weight, if you are overweight;
and quitting smoking.
Your doctor may also recommend medications
that act on your kidneys,
blood vessels,
or heart
to help reduce your blood pressure.
Diuretics, commonly called water pills,
cause your kidneys to move more salt and water
from your blood into your urine,
which reduces your blood volume and pressure.
Beta-blockers reduce the workload on your heart
by decreasing both the rate of your heartbeat
and the strength of your heart's contractions.
Several types of drugs act directly or indirectly to reduce your blood pressure
by relaxing your blood vessels, which increases their diameter.
These drugs include ACE inhibitors,
angiotensin II receptor blockers,
calcium channel blockers,
and direct-acting vasodilators.