Role of the Fusimotor System in Locomotion
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The contribution of muscle spindles to the control of locomotion depends on the patterns of discharge that occur in static and dynamic gamma motoneurones (ysand yo). Discharges of y-axons to the MG muscle were studied during treadmill locomotion in pre-mammillary, decerebrated cats. All ys-efferents increased their rate of discharge at onset of locomotion and were modulated with movement. Type-1 increased their rate with muscle shortening whereas type-2 ysefferents increased their discharge rate during muscle lengthening. The type-1 yspattern appears to be a temporal template of the intended movement. The type-2 yspattern may be appropriate for afferent biasing through bag2intrafusal fibres. TheYoaxons showed an interrupted discharge pattern with sudden onset of firing at the start of muscle shortening and falling quiet shortly after the beginning of lengthening. The yodischarge would prepare primary endings to respond with high sensitivity at the start of muscle lengthening.
KeywordsMuscle Spindle Intrafusal Fibre Ankle Flexion Treadmill Locomotion Locomotor Cycle
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