First of all, to reply to your question we must distinguish between the static and the dynamic state of the cardiovascular system. Static is the roughly equilibrium state when the body is in a relaxed state, and the dynamic mode is when the heart, brain, and blood vessels (arteries etc) are called upon to deliver more oxygenated blood to the bodily organs. The two modes are quite different, but constriction of the blood vessels doesn't increase blood pressure, in either mode. What happens is that when a greater flow of blood is called for (during stress or physical exertion) the BRAIN does three things :- (1) It increases PULSE RATE, the number of times the heart beats per minute, (2) It increases the PRESSURE at which the heart pumps blood out of the heart (blood pressure) and finally, (3) It DILATES the blood vessels (arteries, arterioles, capillaries, etc) of the system to FACILITATE flood flow , i.e., helps it flow easily. So you can see, while dilatation of blood vessels is always associated with increased blood flow, and increased blood pressure, the vessels themselves don't actually cause the high pressure. The pressure is regulated always by the brain and its associated nervous control systems. The medical profession believes that hardening of arteries and other blood vessels with the aging process restricts blood flow and so-called "blood-pressure" rises to compensate for it. But this is a complete fallacy, simply because all research records show that we all develop the same (well, -pretty much the same) pressure "at rest", at the point where the heart ejects blood from the left ventricle into the aorta, (the central aortic pressure) and because the total loop resistance is the same for everyone, young and old, male and female, healthy or sclerotic. It doesn't alter. So "age-related hypertension" is a myth. In fact, all the so-called "normal" or "healthy" pressures they strive for are far too low to drive the known blood flow round the cardiovascular circuit. That is, the "gold-standard" figure of 120/80 can't possibly drive 5 ltres per minute round the vascular loop.