Muscle contraction RyRs are activated by a calcium trigger, which is brought about by the flow of through the L-type calcium channels. Furthermore, cardiac muscle tend to exhibit diad (or dyad) structures, rather than triads. Excitation-contraction coupling in cardiac muscle cells occurs when an action potential is initiated by pacemaker cells in the sinoatrial node or Atrioventricular node and conducted to all cells in the heart via gap junctions. The action potential travels along the surface membrane into T-tubules (the latter are not seen in all cardiac cell types) and the depolarisation causes extracellular to enter the cell via L-type calcium channels
"What Is This Heart?" of 69, based on 32 reviews, which indicates "generally favorable reviews". Ian Cohen of Pitchfork Media gave a very positive review of the album stating, ""What Is This Heart?" makes you initially susceptible and vulnerable, and that’s risky when modern discourse seeks metaphorical blood, allowing people to disclose more than ever without actually revealing anything. So make no mistake, the title of this album is a challenge as well, as How to Dress Well’s modern masterpiece is conducted with the most eternal transparency—Krell asks “what is this heart” and lets you look right into his own." "What Is This Heart?"