What is High Blood Pressure?
When you have your blood pressure taken, your health care provider is measuring the pressure, or tension, that blood exerts on the walls of the blood vessels as it travels around the body. In a healthy person, this pressure is just enough for the blood to reach all the cells of the body, but not so much that it strains blood vessel walls.
Blood pressure is measured in millimeters of mercury (mm Hg).
- A typical normal blood pressure is 120/80 mm Hg, or “120 over 80.”
- The first number represents the pressure when the heart contracts.
- The second number represents the pressure when the heart relaxes.
- Blood pressure greater than 140/90 mm Hg is considered high.
Generally, blood pressure will go up at certain times – for instance, if you smoke a cigarette, win the lottery, or witness a car crash – and will return to normal when the stressful or exciting event has passed.
But when blood pressure is high all the time, the continuous increased force on blood vessel walls can damage blood vessels and organs, including the heart, kidneys, eyes, and brain.
The medical term for high blood pressure is hypertension.
Need to Know:
Systolic and Diastolic Blood Pressure: Blood travels through blood vessels much like water through a garden hose. The blood in the vessels is under pressure just like the water in a hose when the tap is turned on. With each heartbeat more blood is pumped into the vessels – like turning up the tap – so the pressure rises. This is the systolic blood pressure, the first number in the blood pressure measurement, which is normally around 120. Between heartbeats, while the heart is resting, the pressure in the arteries is lower. This is the diastolic pressure, second number in the blood pressure measurement, which is normally around 80.
Indication of high blood pressure
You can increase the pressure in a hose either by turning up the tap or by putting a crimp in the hose (that is, by narrowing the hose). In this same way, the blood pressure in blood vessels will rise if fluid flows more forcefully or if the arteries are narrowed. Pressure in a hose can be regulated either by controlling the rate at which fluid passes through it or by widening it. Likewise, the pressure in the blood vessels can be controlled, with medications that act on the heart or blood vessels and with certain lifestyle modifications.
Need to Know:
Although high blood pressure can be extremely dangerous, it usually causes no symptoms – so many people don’t even realize they have it. High blood pressure can only be detected with accurate and repeated measurements of a person’s blood pressure. That’s one reason why it’s so important to have regular medical checkups.
Even though high blood pressure can be treated safely and effectively, only about one-quarter of people who have high blood pressure take the necessary steps to keep their blood pressure within a normal range.
There are three types of hypertension:
- Primary hypertension (essential hypertension). This is high blood pressure for which no cause can be found. Most people with high blood pressure (90 to 95 percent) have this type of hypertension. Doctors suspect that a combination of lifestyle, diet, heredity, age, gender, race/ethnicity, hormone levels, and other factors all contribute to high blood pressure.
- Secondary hypertension (non-essential hypertension). This is high blood pressure for which a definite cause can be found. This type of high blood pressure accounts for only 5 to 10 percent of all cases of hypertension. Some of these causes are temporary or controllable – for instance, pregnancy or the use of certain medications – while others are chronic conditions like hormonal diseases, kidney disease, or head injuries.
- Isolated systolic hypertension (ISH). Older people are sometimes susceptible to another form of high blood pressure, called isolated systolic hypertension. In people with this condition, blood pressure is higher than normal when the heart beats, but returns to normal in between beats of the heart. The large difference in pressure can place additional strain on artery walls.
Q. If I do not feel any symptoms, is there still a problem?
A. Most people with high blood pressure do not experience any symptoms. The presence of symptoms, such as headache or blurry vision, usually indicates severe or long-standing hypertension. However, over time, uncontrolled high blood pressure causes significant damage to important organs including the heart, kidneys, brain, and eyes. In a number of cases, this damage can lead to death. This is why high blood pressure is sometimes referred to as “the silent killer.”
Facts about high blood pressure
High blood pressure is a condition in which the pressure, or tension, that blood exerts on the walls of blood vessels goes up and stays high, which can damage the blood vessels, the heart, and other organs. It is estimated that more than 50 million Americans have high blood pressure.
High blood pressure is one of the most serious health problems in the United States; yet, because high blood pressure has no symptoms, millions of people do not even know they have it. As many as one in four adults in the United States has high blood pressure.
High blood pressure affects people of all ages, racial and ethnic groups, and walks of life.
Doctors do not know what causes high blood pressure in 90 to 95 percent of people who have it.
High blood pressure is one of the most important risk factors for coronary heart disease.
High blood pressure is the most important risk factor for stroke, which is the third leading cause of death in the United States. High blood pressure is a common cause of heart failure, the leading cause of death in the United States High blood pressure is a common cause of kidney disease.
What Factors Affect Blood Pressure?
Blood pumped through blood vessels is always under pressure, much like water that is pumped through a garden hose. This pressure is highest in the arteries closest to the heart and gradually decreases as the blood travels around the body. Blood keeps moving around the body because there are differences in pressure in the blood vessels. Blood flows from higher-pressure areas to lower-pressure areas until it eventually returns to the heart.
Hypertension is much strain on your heart
Blood pressure is controlled by three things:
- How fast the heart beats (heart rate). The pace at which the heart beats, or heart rate, is counted in heartbeats per minute. Generally, when heart rate increases, blood pressure rises. When heart rate decreases, blood pressure drops.
- A number of things affect heart rate, including the body’s nervous system; chemical messengers called hormones, body temperature, medications, and diseases.
- How much blood the heart pumps with each beat (stroke volume). The amount of blood pumped out of a ventricle with each heartbeat is called stroke volume. When you’re resting, stroke volume is about the same as the amount of blood that veins carry back to the heart. But under stressful conditions, the nervous system can increase stroke volume by making the heart pump harder. Stroke volume can also be affected by certain hormones, drugs, and diseases, as well as increases or decreases in the amount of blood in the body, called blood volume.
Nice To Know:
You might also hear the term “cardiac output” used to describe the amount of blood that’s pumped through the body. Cardiac output is simply the amount of blood pumped out of a ventricle in one minute:
Cardiac output = Heart rate x Stroke volume (amount of blood pumped with each beat).
As cardiac output increases, so does blood pressure. This is why heart rate and stroke volume are important ways for the body to control blood pressure.
How difficult it is for blood to travel around the body (peripheral resistance). The third major component that affects the blood pressure is the caliber or width of the arteries. Blood traveling in narrower vessels encounters more resistance than blood traveling through a wider vessel (its harder for water to pass through a narrow pipe than a wide pipe).
Depending on what a person is doing, the amount of blood the heart pumps varies enormously. Yet the blood pressure normally remains pretty stable. That’s mainly because the body adjusts the resistance of the arteries, either widening or narrowing them as appropriate, to prevent the blood pressure from swinging wildly.
This ability to regulate the width of the blood vessels is called the peripheral resistance. Most of the resistance to blood flow in the circulation occurs in the small-diameter arteries called arterioles.
These arterioles are especially important in the immediate regulation of blood pressure. That’s because they contain specialized smooth muscle in their walls that can relax or contract, allowing the blood vessel to get wider or narrower.