Description of Guyton stress relaxation module

Model Status

This CellML model has been validated. Due to the differences between procedural code (in this case C-code) and declarative languages (CellML), some aspects of the original model were not able to be encapsulated by the CellML model (such as the damping of variables). This may affect the transient behaviour of the model, however the steady-state behaviour would remain the same. The equations in this file and the steady-state output from the model conform to the results from the MODSIM program.

Model Structure

Arthur Guyton (1919-2003) was an American physiologist who became famous for his 1950s experiments in which he studied the physiology of cardiac output and its relationship with the peripheral circulation. The results of these experiments challenged the conventional wisdom that it was the heart itself that controlled cardiac output. Instead Guyton demonstrated that it was the need of the body tissues for oxygen which was the real regulator of cardiac output. The "Guyton Curves" describe the relationship between right atrial pressures and cardiac output, and they form a foundation for understanding the physiology of circulation.

The Guyton model of fluid, electrolyte, and circulatory regulation is an extensive mathematical model of human circulatory physiology, capable of simulating a variety of experimental conditions, and contains a number of linked subsystems relating to circulation and its neuroendocrine control.

This is a CellML translation of the Guyton model of the regulation of the circulatory system. The complete model consists of separate modules each of which characterise a separate physiological subsystems. The Circulation Dynamics is the primary system, to which other modules/blocks are connected. The other modules characterise the dynamics of the kidney, electrolytes and cell water, thirst and drinking, hormone regulation, autonomic regulation, cardiovascular system etc, and these feedback on the central circulation model. The CellML code in these modules is based on the C code from the programme C-MODSIM created by Dr Jean-Pierre Montani.

This particular CellML model describes the effect of stress relaxation on basic venous volume (V0). This model calculates the effect over a period of time caused by excess volume (or too little volume) in the venous tree to cause changes in the volume holding capacity of the venous tree when it is fully filled with blood but at zero pressure. In this model, there are two separate parallel stress relaxations of the veins. One of these has a short time constant (SRK) and the other has a long time constant (SRK2).

A systems analysis diagram for the full Guyton model describing circulation regulation.

A schematic diagram of the components and processes described in the current CellML model.

There are several publications referring to the Guyton model. One of these papers is cited below:

Circulation: Overall Regulation, A.C. Guyton, T.G. Coleman, and H.J. Granger, 1972, Annual Review of Physiology , 34, 13-44. PubMed ID: 4334846