Which characteristic or component is shared by skeletal muscle and smooth muscle?

Question

Quizplus · Accepted Answer

[VI A, B 1-4; VII B 1-4]. An elevation of intracellular $\left[\mathrm{Ca}^{2+}\right]$ is common to the mechanism of excitation-contraction coupling in skeletal and smooth muscle. In skeletal muscle, $\mathrm{Ca}^{2+}$ binds to troponin $\mathrm{C}$, initiating the cross-bridge cycle. In smooth muscle, $\mathrm{Ca}^{2+}$ binds to calmodulin. The $\mathrm{Ca}^{2+}$-calmodulin complex activates myosin light chain kinase, which phosphorylates myosin so that shortening can occur. The striated appearance of the sarcomeres and the presence of troponin are characteristic of skeletal, not smooth, muscle. Spontaneous depolarizations and gap junctions are characteristics of unitary smooth muscle but not skeletal muscle.

Which Characteristic or Component Is Shared by Skeletal Muscle and Smooth