Guide to Blood Pressure

Blood pressure is one of the vital signs checked by health professionals during checkups and exams, and it's used to evaluate people who are severely wounded. It is very important to your circulatory system and your general health that blood pressure be kept in check, because health problems will occur if your blood pressure is too low or too high.

Definition

• Blood pressure is the pressure placed on the walls of the blood vessels as blood flows through the body. The beating of the heart keeps the blood circulating, and blood pressure decreases the farther from the heart it is measured. Usually, when someone refers to blood pressure he means brachial blood pressure, which is measured in the upper arm.

Measurement

• When you go to a doctor's office, your blood pressure is measured by a device called a sphygmomanometer. This is the inflatable cuff usually attached to a device that measures the pressure exerted against the cuff. Blood pressure is measured in two ways. The first is the systolic blood pressure, at the peak of pressure when blood vessels are contracting to push blood through. The second is the diastolic blood pressure, the lowest pressure exerted by the blood when blood vessels are at their widest. The systolic blood pressure is written over the diastolic. A normal blood pressure for an adult is 115/75.

Physical Factors

• Blood pressure can be affected by many things, most of which are physiological. For example, the amount of blood present in the body, which is related to a person's salt intake (more salt equals more blood), affects the blood pressure. If there is more blood, blood pressure will rise. The viscosity, or thickness, of the blood also affects blood pressure. More viscous blood yields a higher blood pressure, and this can occur when there is an excess of sugar in the blood. One other physical factor affecting blood pressure is the heart rate. The faster a person's heart rate is, the higher his blood pressure will be.

Regulation

• There are three systems that affect the internal regulation of blood pressure throughout the body. One is the release of aldosterone, which is a steroid hormone produced by the adrenal gland. This stimulates sodium retention, which in turn affects blood retention and blood pressure, since sodium has a direct effect on the blood. The rennin-angiotensin system (RAS) also regulates blood pressure. When there is a drop in blood pressure, the RAS releases a chemical that constricts the blood vessels so that blood pressure rises. The baroreceptor reflex is the third blood pressure regulator. Barorecepters note changes in blood pressure and send signals to the brain stem, which then changes the heartbeat in order to regulate blood pressure.

Hypertension and Hypotension

• Hypertension is more commonly known as high blood pressure, which is defined as blood pressure over 140/90. Hypertension puts more stress on the heart and makes it work harder, which leads to an increased risk of stroke, heart attack and heart disease. Hypotension is low blood pressure, under 90/60. This is a problem only when there are symptoms, which can include dizziness and fatigue. When this occurs, consult your doctor because hypotension can lead to shock.