Because of the elastic properties of vessels, the pressure-flow relationship of passive vascular beds in non-linear △P Blood flow Resistance(r) aLI Dilated R= Rigid tub Autoregulating Constricted 06 200 Critical closing pressure Perfusion Pressure(mmHg) 9Because of the elastic properties of vessels, the pressure-flow relationship of passive vascular beds in non-linear Blood flow = ΔP Resistance (R) R= 8Lη πr 4 Rigid tube 6 Critical closing pressure 9