Dynamic response is due to

Nuclear bag fibers are thicker, longer and fewer in numbers. They have a bag or bulge in the centre where the afferent fibers received are Aα type with primary ending (Annulospiral). The efferent fibers are Aγ1, which are dynamic fibers with ‘plate ending’. Nuclear chain fibers are thinner, shorter and more in numbers. They do not have a bulge, but receives afferent fibers of type Aα with primary ending (Annulospiral). The peripheral part also receives afferent fibers of type Aβ with secondary ending (Flower spray). The efferent fibers are Aγ2 static fibers with ‘trail ending’.