millimeters of mercury (expressed as mm Hg) and the diastolic blood pressure is usually 80 mm Hg in the healthy person. They represent the blood pressure during contraction of the heart and the blood pressure during relaxation of the heart, respectively. The pulse pressure is the difference between the systolic and diastolic blood pressure, which should be about 25 percent of the systolic blood pressure. A low pulse pressure is described as being “narrow.” A narrow pulse pressure can be seen in aortic stenosis, congestive heart failure, and blood loss/low blood volume. A wide or high blood pressure can be seen after strenuous blood pressure in healthy people. Chronically high pulse pressures can cause organ damage. The mean arterial blood pressure or MAP is the average blood pressure in the arteries, it is a complicated number that must be calculated. A normal MAP is about 70-110 mm Hg; a low MAP means the possibility of low blood flow and ischemia to the organs and tissues. The blood pressure is measured (usually) by checking the pressure in the upper arm using a sphygmomanometer, which measures the pressure on a measuring device and uses a stethoscope to listen to Korotkoff sounds, which are sounds created by turbulent flow in the artery when the cuff is deflated. The pressure when the Korotkoff sounds begin is called the systolic blood pressure, while the blood pressure when the Korotkoff sounds end is the diastolic blood pressure. Things that affect the blood pressure and blood flow to the rest of the body include cardiac output, compliance of the arterial walls, blood volume, blood viscosity, and blood vessel length and diameter.
REGULATION OF THE CARDIOVASCULAR SYSTEM Blood pressure must be sufficient to provide adequate blood to the tissues on a continual basis. During exercise, blood flow is preferentially directed to the skeletal muscle, lungs, and heart. After a meal, blood flow is preferentially directed to the digestive system. The only organ that continually receives blood regardless of the situation is the brain. Blood must go to the skin during exercise as well in order to dissipate the generated body heat.
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