Myotatic Reflex: Its Input-Output Relation

The dynamic properties of the myotatic reflex and of its components were determined by a systems-analysis approach. The gain and phase relations between an applied stretch, which initiates the reflex, and the output of the primary muscle spindles, which impinge upon α-motoneurons, are not further changed by the properties of the motoneurons. The dynamic relation between motoneuron activity and the resultant muscle tension balances these changes in gain and phase; the result is a flat gain and nearly zero phase difference between stretch and tension produced by the myotatic reflex. Moreover, the distribution of activity in multiple channels extends the range in which the overall reflex is linear.