Cooperation among Heart Rate, Respiration and Locomotion Rhythms and Homeodynamics---Experimental and Theoretical Study

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Homeodynamics is an extended concept of the homeostasis of living organisms.As in the latter, it is associated to the control of the inner state of the living organisms by the central nervous system including the autonomic nervous system.Rhythmic activities such as heart beats, respiration and even locomotor activity may be observable variables which reflect or influence the homeodynamic control.This study aims understanding basic mechanism of emergence of the homeodynamic control based on these observable variables (measured data).The rhythmic activities mentioned above share the common property referred to as dynamic stability which is the characteristics of nonlinear dynamical systems.That is, the system state always changes in time, but that varied state is stable against external perturbations.To understand the basic properties of the underlying systems associated to the homeodynamic control, it is necessary to identify/model the underlying system and then consider functional role … More of the dynamic stability.We have done the following studies along this line.1. Quantitative analysis of the dynamic stability.We analyzed two cases associated to the dynamic stability and homeodynamics.A : Dynamic stability estimation and then modeling of the locomotion rhythm.B : Simulation study of the instability of the cardiac rhythm and transition to cardiac arrhythmias.The instability of the dynamic stability in relation to cardiac physiology was exemplified.2. Identification and modeling of unknown nonlinear systems from time series data.We developed practical methods to estimate unknown nonlinear dynamical system from time series data.It is natural to assume the underlying nonlinear dynamical system is parametrized by several parameters which may take constant values, but be varied for long time range.The system may exhibit qualitatively different dynamics depending on these parameter values (bifurcations).Our methods can be utilized to estimate the model parametrized by several parameters which may be altered during the measurements.The methods may be applicable to model heart rate variability/control due to autonomic nerve activities. Less