The observation of biological systems suggests the hypothesis that nonlinear mechanisms could be involved in the control of their functions. The analysis of cardiovascular system, starting from the measurement of its state variables, seems to confirm the nonlinear nature of the control mechanisms and the presence of fractal structures in those signals. The goal of this study is to verify if a physiological control system is able to generate complex and also chaotic dynamics when periodically forced by a sinusoidal input at different frequencies. The paper analyzes a simple physiological model which accounts for the oscillations in the arterial blood pressure signal generated by the action of the baroreceptive control. The model was proposed by Kitney in 1979 and it considers the effect of the respiration signal like an external periodically forcing term. Using this model, a variety of nonlinear behaviors like the frequency entrainment, the phase locking and the frequency shift can be reproduced in different experimental situations. A study of the dynamics of the baroreceptive model through a structural stability analysis is proposed. The bifurcation diagrams classifies the different dynamical behavior of the model for different values of respiratory frequency and gain of baroreceptive system parameters. Other model parameters are fixed at realistic values. The large number of bifurcations of different types indicate that the dynamics of the model can be very complex. In fact, for values of parameters in physiological range, multiplicity of attractors, subharmonics of various periods, period doublings, quasiperiodic solutions and strange attractors get up. Results are in agreement with the hypothesis that a nonlinear dynamic model underlines the variability control.

Bifurcation analysis of a physiological model of the baroreceptive control

Signorini M. G.;Cerutti S.
1997-01-01

Abstract

The observation of biological systems suggests the hypothesis that nonlinear mechanisms could be involved in the control of their functions. The analysis of cardiovascular system, starting from the measurement of its state variables, seems to confirm the nonlinear nature of the control mechanisms and the presence of fractal structures in those signals. The goal of this study is to verify if a physiological control system is able to generate complex and also chaotic dynamics when periodically forced by a sinusoidal input at different frequencies. The paper analyzes a simple physiological model which accounts for the oscillations in the arterial blood pressure signal generated by the action of the baroreceptive control. The model was proposed by Kitney in 1979 and it considers the effect of the respiration signal like an external periodically forcing term. Using this model, a variety of nonlinear behaviors like the frequency entrainment, the phase locking and the frequency shift can be reproduced in different experimental situations. A study of the dynamics of the baroreceptive model through a structural stability analysis is proposed. The bifurcation diagrams classifies the different dynamical behavior of the model for different values of respiratory frequency and gain of baroreceptive system parameters. Other model parameters are fixed at realistic values. The large number of bifurcations of different types indicate that the dynamics of the model can be very complex. In fact, for values of parameters in physiological range, multiplicity of attractors, subharmonics of various periods, period doublings, quasiperiodic solutions and strange attractors get up. Results are in agreement with the hypothesis that a nonlinear dynamic model underlines the variability control.
1997
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/1107989
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