Figure 1.

The Figure shows an illustration of part of an atrial myocyte. The arrows denote the movement of Ca²⁺ ions as a centripetal wave. The Ca²⁺ wave propagates via CICR between neighbouring clusters of RyRs. In the presence of InsP₃, Ca²⁺ wave propagation is boosted by the opening of InsP₃Rs. Both Ca²⁺ and InsP₃ can pass through nuclear pore complexes (NPC), and trigger nucleoplasmic Ca²⁺ signals that influence gene transcription. Mitochondria sequester Ca²⁺ ions, and thereby retard Ca²⁺ wave propagation.