伸張反射張力の推定による脳の伸張反射調節機構の解明(1部生体を知る)

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The present study aims to estimate the force of stretch reflex origin (short-latency and long-latency reflex) separately from measured stretchevoked force with the aid of a mathematical muscle model, and to examine the extent to which the brain can modulate the reflex in different tonic forces and in different kinds of instructions given the subject against mechanical perturbation. A small ramp stretch was applied to the human flexor pollicis longus muscle at an unpredicted time while the subject maintained a constant flexing tonic force. The amount of stretch was 2.4 degrees and the duration of stretching was 15 msec, which were both identical in all the experiments. The instructions given the subject prior to the experiment were either "let go" or "do not react" or "resist." The results are summarized below. (1) The force developed by the short-latency reflex (SR) commenced approximately at 35 msec after the onset of stretch and the force by the long-latency reflex (LR) at approximately at 60 msec. The voluntary reaction time, which depended on the subject, ranged from 117 to 172 msec. (2) The response of the stretch model agreed closely with the measured force during the period of 35 msec just after the onset of stretch, which originated only from the muscle viscoelasticity and passive components such as skin, joint and moment of inertia of the thumb. (3) The force of SR and LR was estimated by subtracting the viscoelastic force of muscle (model response) from the stretchevoked force. (4) The force of SR was averaged during the period from 35 to 60 msec, and the force of LR from 60 msec to the voluntary reaction time. The averaged force is defined as the reflex responsiveness. (5) Both reflex responsiveness of SR and LR increased with an increase in tonic force. (6) Reflex responsiveness of SR and LR were 18% and 75% of the stretch-evoked force, respectively, under the instruction "do not react." (7) Reflex responsiveness of SR did not change significantly at the same tonic force with varying instructions. This suggests that neither the muscle spindle gain nor excitability of the alpha-motoneuron pool can be modulated by the brain in costant tonic contraction. (8) Reflex responsiveness of LR was greatest in "resist," which was approximately 90% of the stretch-evoked force, and smallest in "let go," which was approximately 15% of the stretch-evoked force. (9) These results imply that the stiffness of motor servo can vary with tonic force and instruction, and that the stretch reflex, in particular, LR, would assist in regulating the muscle length with muscle viscoelasticity. Further, reflex gain of the transcortical path or spinal poly-synaptic path can be modulated according to the instructions given the subject by the brain.
バイオメカニズム学会の論文
1986-09-25

伸張反射張力の推定による脳の伸張反射調節機構の解明(1部生体を知る)

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伸張反射張力の推定による脳の伸張反射調節機構の解明(1部 生体を知る)

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伸張反射張力の推定による脳の伸張反射調節機構の解明(1部生体を知る)