So does this mean that when peripheral blood vessels are constricted due to SNS activity that the blood vessels in the brain will dilate to compensate for the high systemic blood pressure as a kind of protective mechanism to prevent over perfusion? I ask because I have been prescribed propanalol for migraine and when I started reading about how propanolol or beta blockers in general impact migraine I read that it reduces vasodilation of the cerebral blood vessels which had me confused as I thought beta blockers were used to treat high blood pressure and therefore would rather increase vasodilation than decrease vasodilation reducing PVR? It appears beta blockers and the sympathetic nervous system have a counter effect on the cerebral blood vessels vs peripheral/systemic blood vessels?