unpredictability, the overall system of spinal integrity would reflect a loss of stability commensurate with the extent of impairment to its maintenance subsystem(s). It is important to emphasize that all body systems are normally functioning far from equilibrium. They are highly responsive, even though their bodily function may suggest otherwise. The skeletal muscular system, for example, appears very constant in regard to posture maintenance. It is its highly responsive (far from equilibrium) state, however, that permits the gross perception of constancy. Alternatively, emotions appear to fluctuate during the maintenance of expression. Holstege, 1992 has proposed that the Emotional Motor System contributes fibers to every spinal level and controls the gain (threshold) of neurons at every spinal level. This system is further proposed to dissipate tension from the limbic brain through large muscle movements. Vocalization and other mechanisms include "wave like" motions of the trunk, head turning, and limb motion.

All systems associated with emotion are also far from equilibrium, but the expression of their function is one of rapid variability, not constancy. Consequently, the function of a system, constancy versus rapid fluctuations, should not be misinterpreted as one system being far from equilibrium, while the other is not. When systems, regardless of their biological function, lose their integrity, they are also drifting toward thermodynamic equilibrium. If the loss of integrity is severe enough or if it is of sufficient duration, thermodynamic equilibrium may be approached. In this condition, not only does the system lose integrity, but also the life of the organism may be threatened.

Conditions surrounding impairment of maintenance subsystems could promote a pattern of insults, including aberrant joint function, altered tension and oscillation patterns of soft tissues of the spine, alteration of the integrity of cell membranes, and inhibition of the flow of neurological information. Such a complex could readily create mechanical spinal cord tension. Any of the components of this type of complex is believed to be sufficient to inhibit, but not necessarily eliminate, the normal integration of all subsystems involved in the maintenance of spinal integrity. Consequently, unpredictable outcomes manifest, which may be asymptomatic in the early onset of the subluxation or may express any combination of symptomatology and dysfunction (Leach, 1986).

Coupling, or linking, of synergistic subsystems in regard to successful coordination is exemplified in the theory of Panjabi (1992), who hypothesized that spinal stability is dependent upon three interacting subsystems. The first is described as the Passive Subsystem (vertebrae, discs, and ligaments). In this subsystem, ligaments contribute to spinal stability towards the ends of normal ranges of motion by overstretching. The discs can be subjected to degeneration or tears and fissures in the annulus. Vertebrae are subject to microfractures. All or any of these components of the Passive Subsystem act as signal producers (transducers) that measure changes in spinal position and motion. The second subsystem, the Active Subsystem (muscles and tendons) acts as the means through which the Neural Control Subsystem generates forces affecting stability to the spine. The magnitude of force generated is signaled by the tendons, acting as transducers. The third subsystem is the Neural Control Subsystem

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