Calcium regulation in cardiac cells

Calcium is a common signaling mechanism, as once it enters the cytoplasm it exerts allosteric regulatory affects on many enzymes and proteins. Calcium can act in signal transduction after influx resulting from activation of ion channels or as a second messenger caused by indirect signal transduction pathways such as G protein-coupled receptors. Movement of calcium ions from the extracellular compartment to the intracellular compartment alters membrane depolarisation. This is seen in the heart, during the plateau phase of ventricular contraction. In this example, calcium acts to maintain depolarisation of the heart. Source: [[wikipedia:Calcium_signaling|Wikipedia]]

钙作为一种普遍的信号传导机制，其进入细胞质后，对众多酶和蛋白质产生变构调节效应。钙离子在离子通道激活后的内流过程中，可以参与信号转导，或作为由G蛋白偶联受体等间接信号传导途径引发的第二信使发挥作用。钙离子从细胞外空间向细胞内空间的迁移，改变了细胞膜的极化状态。这一现象在心脏的室缩平台期尤为明显。在本例中，钙离子发挥着维持心脏去极化的作用。来源：[维基百科：钙信号传导](https://zh.wikipedia.org/wiki/Calcium_signaling)