Transition in sensitivity of spindle receptors that occurs when muscle is stretched more than a fraction of a millimeter

Experiments on cats were designed to characterize the transition from a region of high sensitivity to one of lower sensitivity. We have chosen as inputs a family of ramp stretches that differ from each other by scaling factors. The smallest ramps lie within the region of linear behavior, whereas the larger ones pass beyond the linear region. Because the ramps were delivered slowly and smoothly and because the responses of deefferented spindles to these changes in length were highly reproducible, we were able to study in some detail the transition to lower sensitivity, as well as the discontinuities in the slopes of individual responses that appear to correspond with the transition.