On the surface, hypertension is a disease of the arteries: when blood vessels constrict, blood pressure rises--it’s the simple physics involved when a large volume of fluid has to move through a smaller vessel.
However, blood pressure is also dependent on the central nervous system. Under normal circumstances, nerves that are connected to the arteries cause them to dilate when pressure increases. But for certain people these mechanisms may become impaired. Read more - http://www.newswise.com/articles/view/551432/