In both skeletal and cardiac muscle excitation-contraction (E-C) coupling, depolarization conduction and Ca2+ release processes occur. However, though the proteins involved are similar, they are distinct in structure and regulation. The dihydropyridine receptors (DHPRs) are encoded by different genes, and the ryanodine receptors (RyRs) are distinct isoforms. Besides, DHPR contacts with RyR1 (main RyR isoform in skeletal muscle) to regulate Ca2+ release in skeletal muscle, while the L-type calcium channel (DHPR on cardiac myocytes) and RyR2 (main RyR isoform in cardiac muscle) are not physically coupled in cardiac muscle, but face with each other by a junctional coupling.