Fig. 6. Autoregulation of flow.

At constant arterial oxygen content, an increase in cardiac output causes a disproportionate increase in arterial pressure (solid line). This signifies a resistance to flow that is much lower at low flows than at high flows (the sloped dashed lines are lines of constant resistance, low resistance at the left end of the curve and high resistance at the right end). Autoregulation translates minor changes in flow into large changes in pressure.