Critique of a large-scale organ system model: Guytonian cardiovascular model.

Abstract

This paper reviews Guyton's model, which is large not only in the number of its components but also in the time scale that it spans. The evolution of this model is explained in three stages. To explain short-term regulations of cardiac output Guyton started with a drastically simplified model of the entire cardiovascular system, which emphasized the role of blood volume and the vascular capacity. Guyton's group then directed its efforts toward the analysis of long-term regulation of arterial pressure. Two slow-acting mechanisms were added to the model: (1) the marked increase or decrease of urinary output with only slight increase or decrease in arterial pressure (the renal function curve in the Guytonian model), and (2) long-term vascular autoregulation. This second-stage model explained the transient dynamics and steady equilibrium in renal hypertension. The current version of Guyton's model incorporates a variety of additional endocrine and neural mechanisms that parametrically control the renal function curve. The Guytonian model is a unique venture in modern cardiovascular physiology because of its size and the investigators' incessant efforts to test it against the real system behaviors.