Dynamic analysis of higher order biological systems.

Humans and animals consist of a variety of bio-systems exhibiting various bio-phenomena over the course of time, from the past to the present and into future, up to just before their death. Each state of a bio-phenomenon at any time is related in stochastic fashion not only to its past history, but those of many other bio- and natural phenomena, enormous in number, in their internal and external environments. Most states of these bio-phenomena sway more or less around respective averages, which suggest their levels of homeostasis, essentially important for maintaining life. In the above past history of sway was hidden an essential characteristic, i.e., dynamic higher-order activity, of the bio-system, whereas the bio- and natural phenomena in the environments act to drive, i.e., stimulate, as an ensemble, the bio-system to exhibit the bio-phenomena as its responses. From this new point of view, mono- and multivariate dynamic stimulation-system (activity)-response relations in stochastic fashion can be seen as an extension leading from of one of the most fundamental static laws of excitability, that is the threshold stimulus-excitability-unit response relation in physiology. The dynamic mono- and multivariate higher-order activities, each of which consisted of some first- and second-order component activities, can be described in the frequency and time-patterns as the power spectral densities or frequency responses and (unit) impulse responses, respectively. Some of these "dynamic activities" were manifested in the brain system of humans and cats, the human "posture holding system," "the pressure regulatory system" in the human pulmonary circulation and the "glucoregulatory system" of dogs, respectively.