47.6 The Release of Ca2+ from the Sarcoplasmic Reticulum Triggers Muscle Contraction When Ca2+ binds to troponin, it exposes actin-myosin binding sites. As long as binding sites and ATP are available, the cycle of actin and myosin interactions continues, and the filaments slide past each other.
Calcitonin Calcium (Ca2+) plays a significant role in both nervous conduction and muscle contraction. It is also necessary for coagulation (clotting) of blood. The blood calcium level is regulated in part by calcitonin, a hormone secreted by the thyroid gland when the blood calcium level rises (Fig. 10.7).