Control of Blood Pressure

Blood pressure is continuously monitored and adjusted, from moment-to-moment, to meet physiological demands. In order to ensure that all tissues are adequately perfused with blood the systolic pressure must exceed 90 mm Hg. However sustained systolic pressures greater than 140-150 mm Hg are known to precipitate damage to the vessel wall and the development of atherosclerotic lesions.
If the physiological demands change then blood pressure changes rapidly to meet them. For example if you stand up from a lying position or run up a flight of stairs your blood pressure will be adjusted (increased) to allow you to do those things.

Additional Information

Atherosclerotic
Atherosclerosis is the major cause of coronary heart disease and is characterised by a narrowing of the arteries, particularly those supplying the heart. This is due to deposits of cholesterol on the inner surface of the vessel wall and proliferation of vascular smooth muscle in the tunica media.