Muscle Control System Model with Feedback from a Muscle Spindle

摘要: Aim The aim is to present a new computer model of a stretch reflex. Reflex path under study involves models: of the spindle and its single Ia afferent fiber,(monosynaptically connected with) a single Mn, which innervates the motor unit in the muscle. The simple model of the muscle dynamics is implemented. It enables to simulate muscle behavior evoked by the Mn activity or external load changes. Methods The overall model (reflex path and the muscle) is implemented in GENESIS environment. The model of neural fibers is based on compartments. The muscle model bases on mechanical Hill model. The spindle model is based on experimental data fitting. In the experiment the muscle was stretched with constant velocity and evoked Ia fiber activity was recorded. The time constants of the Ia-Mn synapse EPSP are identified from intracellular potential of the Mn body, recorded in vivo during stimulation of afferent fibers. Results Dynamics of the Ia, Mn and synapse obtained with these models are consistent with the physiological observations. The spindle modeled as non-linear PID dynamics gives response to changes of the muscle length, which is very similar to this recorded in the in vivo experiment. Muscle model enables to evaluate the muscle length changes. The whole system responds to the external force changes by producing oscillations of the contraction force and the muscle length. The average contraction force is equal the external force and the muscle length is close to the initial value. Conclusions The model reveals that the muscle spindle acts similar to PID dynamics. This can be explained by its main function to maintain zero velocity …