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.
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.
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.
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.
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.
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.
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.”
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.
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.
1 – 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.
3 – 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.
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:
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 the
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.