Figure 2.

The relationship between blood flow and perfusion pressure in rat middle and posterior cerebral arteries. The autoregulatory region extends from ∼60 to 130 mm Hg and is indicated by the shading. The presence of a myogenic response maintains flow constant over a wide range of pressure. Outside the autoregulatory range, there is too little flow at <60 mm Hg and, at high pressure, force generation by vascular smooth muscle cells is insufficient to counteract the distending force of intracellular pressure, resulting in forced dilatation and too much flow.