<Li> 2) Fusimotor set: Gamma motoneurons are activated according to the novelty or difficulty of a task . Whereas static gamma motoneurons are continuously active during routine movements such as locomotion, dynamic gamma motoneoruns tend to be activated more during difficult tasks, increasing Ia stretch - sensitivity . </Li> <Li> 3) Fusimotor template of intended movement . Static gamma activity is a "temporal template" of the expected shortening and lengthening of the receptor - bearing muscle . Dynamic gamma activity turns on and off abruptly, sensitizing spindle afferents to the onset of muscle lengthening and departures from the intended movement trajectory . </Li> <P> It is also believed that muscle spindles play a critical role in sensorimotor development . </P> <P> After stroke or spinal cord injury in humans, spastic hypertonia (spastic paralysis) often develops, whereby the stretch reflex in flexor muscles of the arms and extensor muscles of the legs is overly sensitive . This results in abnormal postures, stiffness and contractures . Hypertonia may be the result of over-sensitivity of alpha motoneurons and interneurons to the Ia and II afferent signals . </P>

Role of muscle spindle in voluntary motor activity