The regulatory mechanism of rat estrous cycle is described as a single closed loop mathematica lmodel, which is composed of subsystems synthesized by the state space method. These are the hypothalamus, hypophysis, ovary, descending and ascending hypophyseal portal systems, general circulatory system and clearance system including the liver, kidney and submandibular gland. Each subsystem is first synthesized as an open loop system and then unified into a single closed loop system, which is mathematically and physically different from the conventionally proposed open loop models.
In this study the light is the only one input taken into account for the whole system, which shows its own dynamic characteristics caused by the change in internal state variables and parameters, once their initial values are set. We here consider “eigenvalues” of system matrices, which characterize the dynamics of the main subsystems and are assumed to remain unchanged during the estrous cycle. We can, however, observe drastic change in internal state variables (e. g. hormones) of the whole regulatory system caused by the change in some of the gains of the subsystems with many complicated interaction loops.
Under these assumptions we have attempted to explain the dynamic characteristics of the regulatory mechanism in the normal estrous cycle and pattern change in the form of estrous cycle corresponding to the slight change in parameters. Further we have carried out model experiments by modifying the values of state variables corresponding to the acute change in the hormone concentrations and ovariectomy.
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