Abstract
As the first step of the cybernetic studies on the muscular movement, the proprioceptive reflex was analysed mainly on the basis of classic control theory. The fundamental proprioceptive reflex arc has two groups of proprioceptor, the muscle spindle (MS) in intrafusal muscle fibre and the tendon organ (TO) in the tendon of extrafusal muscle fibre.
From the location of each receptor, it is considered that MS is a length detector and TO is a tension detector.
At first, the linear analysis was undertaken on the reflex system composed of the muscle (which produces an active force and has series and parallel visco-elastic elements), external load (which includes spring, mass and damper) and the nervous system (receptors, afferent nerves, motor centre efferent nerves).
The stability of the system was examined by the Hurwitz's criterion, and it was indicated that by the increase of the gain of the MS loop (changes in active force: change in muscle length) the system tends to be unstable, while the increase of the TO loop (change in active force: change in muscle tension) improves the system's stability and increases the damping in transient response.
It was clearly shown that the so-called “clasp knife phenomenon”, a kind of flip-flop, cannot be produced by physiological character of TO as believed by most physiologists but the positive feedback loop of some species of MS (the second kind of receptors and group II afferent fibres) is the cause of this phenomenon. Some of the muscle spindles have marked differential character which improves the stability of the system.
Furthermore, other various physiological factors which had not yet been explicated were thus elucidated. We have made also the nonlinear system analysis and got a good agreement with the linear system analysis about the important points.
