Multi-loop representation of the segmental muscle stretch reflex. Its risk of instability

The multi-channel system of the segmental muscle stretch reflex arc is modelled as an arrangement of two or three parallel "component" loops coupled to each other at spinal and at muscle level. Such a model is thought to be more realistic than the usually adopted representation of the stretch reflex as a single negative feedback loop. Anatomical and physiological data were taken from the literature for an extensive simulation of the compound system with special reference to the problem of its stability. Particular emphasis was put on the question of which kind of central (spinal) connectivity is appropriate to best reduce the risk for instability which arises easily in certain system configurations. This paper describes the system and presents simple introductory computations apt to demonstrate the problems the physiological system has to cope with.