A Model for Muscle Contraction in Which Cross-Bridge Attachment and Force Generation Are Distinct

Abstract

This model is based on that recently jpresented by A. F. Huxley and R. M. Simmons (1971). Its most basic assumption is that the attachment and force-generating steps are completely separate; i.e., there is no force present when a cross-bridge attaches to the thin filament; the force is generated, following attachment, by a flip of the cross-bridge head into a different conformational state. In order to model other known muscle phenomena besides those studied by Huxley and Simmons, the model was extended to include attachment and detachment of cross-bridges and continuous motion of the filaments. The model can be related to current ideas of the biochemistry of the contraction cycle. A possible chemical scheme is shown in Fig. 1A.