Think of your heart, arteries and arterioles as a system of garden hoses that end in little nozzles (the arterioles). If you decrease the volume of spray from the nozzle, the hose becomes firm under increased pressure. It is under tension. Less water is flowing through, but it shoots out to a greater distance. Closing down the nozzle regulates the rate and pressure at which the water flows.

Something similar happens in hypertension. The arterioles tighten down; the heart has to work harder to pump blood through the tissues at a nearly normal rate. This maintains the pressure in the arteries and artioles.

Arterial hypertension, or high blood pressure, is a dangerous ailment because of its effect on the walls of the arteries. It accelerates the ailment of atherosclerosis. Many people without high blood pressure have atherosclerosis; but those with high blood pressure have much more severe cases of the illness.

As we have said, the inside of a normal artery is quite smooth and flexible. There is plenty of room for the blood to flow through. However, in the later years of life, there is a tendency for the blood vessels to harden and the muscles to become less flexible.

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