Pressure and flow: are these the true vascular neuroeffectors?

Activity of the efferent nerve supply to the vasculature results in local increases or decreases in the tone of the vascular smooth muscle cells with corresponding changes in diameter. This results in changes in pressure and flow, both of which, because they too influence the vascular wall, extend the influence potentially to the entire bed. As the vascular bed is sensitive to pressure - an increase causing vasoconstriction - and to flow - an increase causing variable amounts of contraction and relaxation - the final results must reflect their interaction. Thus, the direct changes in artery tone brought about by neural activity are modified and diffused throughout the entire regional arterial system by the concomitant changes in the flow and pressure of the blood.