The control of blood pressure involves incredibly sophisticated and complex checks and balances. Blood pressure represents a measure of the amount of blood pumped out by the heart and then the vessels into which this blood is pumped.
The amount of blood pumped out by the heart is controlled by two factors: firstly, the volume of blood returning to the heart from the rest of the body and, secondly, the actual muscular pumping of the heart itself. The vessels into which this blood in turn is pumped are also controlled by two major mechanisms: the sympathetic nervous system (central control by the brain) and, secondly, by the inner lining of the actual vessel (called endothelium), which produces an enormous quantity of chemical substances which in turn control the tone of the vessel (either dilating or constricting the vessel).
It is obvious that anything going wrong with any of the above mechanisms can and, in fact, will result in abnormalities of blood pressure. Most people with elevated blood pressure (hypertension) have some abnormality with more than one of the above mechanisms and often have two, three or more reasons why pressure is up! This explains why many people with hypertension need two or more therapeutic agents to treat their hypertension.
As we learn more about blood pressure and its mechanism of control, it becomes more compelling than ever to try to counteract the various abnormalities for maximal protection against the ravages of elevated pressure, such as stroke, heart attack, heart and kidney failure, and the development of vascular disease generically.
