These processes center on the supply of adenosine triphosphate (ATP) for the actomyosin ATPase of the crossbridges.
Energy sources are numbered in order of their proximity to the actual reactions of the crossbridge cycle. Energy is used by the cell in the A, B, and C order shown. The scheme shown here is typical for all types of muscle, although there are specific quantitative and qualitative variations. ADP, adenosine diphosphate; PCr, phosphocreatine; SR, sarcoplasmic reticulum.
Medical Physiology: Principles of Clinical Medicine