Model number


Two compartment model with feedback control of precursor (pregnenolone) to cortisol and its adrenal secretion.


 This two compartment model for substances, Q1 (precursor) and Q2 (cortisol)
 is simplified from the original models of Urquhart (1968) by Jacquez (1972).
 Precursor Q1 is formed at a rate inhibited by itself at higher concentrations.
 Its conversion to cortisol is stimulated by ACTH, a saturable process. Increases
 in ACTH deplete PREG concentration and increase the secretion from the adrenal.

fig 1

Figure: (Top) Concentration response of cortisol and precursor to ACTH infusion. Q1 is concentration of precurosr in compartment 1 and Q2 is cortisol concentration in compartment 2. (Bottom) ACTH input as a function of time.


The equations for this model may be viewed by running the JSim model applet and clicking on the Source tab at the bottom left of JSim's Run Time graphical user interface. The equations are written in JSim's Mathematical Modeling Language (MML). See the Introduction to MML and the MML Reference Manual. Additional documentation for MML can be found by using the search option at the Physiome home page.

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 Urquhart J and Li CC. The dynamics of adrenocortical secretion. Am J Physiol 214: 73-85, 1968.
 Jacquez JA. Compartmental analysis in biology and medicine.
  Kinetics of distribution of tracer-labeled materials. Amsterdam:
  Elsevier Publishing Co., 1972, pp.237 (See pp 213-216)
 Jacquez JA. Compartmental analysis in biology and medicine. 
  3rd ed.. Ann Arbor, MI: BioMedware, 1996, 514 pp.


Key terms
multiple compartments
steady state
control system
step response
mathematical model
analog computer

Please cite in any publication for which this software is used and send one reprint to the address given below:
The National Simulation Resource, Director J. B. Bassingthwaighte, Department of Bioengineering, University of Washington, Seattle WA 98195-5061.

Model development and archiving support at provided by the following grants: NIH U01HL122199 Analyzing the Cardiac Power Grid, 09/15/2015 - 05/31/2020, NIH/NIBIB BE08407 Software Integration, JSim and SBW 6/1/09-5/31/13; NIH/NHLBI T15 HL88516-01 Modeling for Heart, Lung and Blood: From Cell to Organ, 4/1/07-3/31/11; NSF BES-0506477 Adaptive Multi-Scale Model Simulation, 8/15/05-7/31/08; NIH/NHLBI R01 HL073598 Core 3: 3D Imaging and Computer Modeling of the Respiratory Tract, 9/1/04-8/31/09; as well as prior support from NIH/NCRR P41 RR01243 Simulation Resource in Circulatory Mass Transport and Exchange, 12/1/1980-11/30/01 and NIH/NIBIB R01 EB001973 JSim: A Simulation Analysis Platform, 3/1/02-2/28/07.