inward outward 13 Phase 4 Gene/protein Na’ current SCN5A/Nav 1.5 Ca L-typ CACNA∥Cav1.2 Action current L T-type CACNA1G.∥cav3.1.32 potential transient KCND3/Ky 4.3 and ion outward current KCNA4/Kv 1.4 transport KCNA1/KVLQT 1 delayed rectifiers KCNH2/hERG (k) KCNA5/Kv 1.5 CFTR/CFTR Fast response cell inward rectifier, IK1 三 KCNJ1/Kir 2.1 pacemaker current↓ J HCN2,4/HCN2,4 Na*-Ca2* exchange SLC8A1/NCX 1 Na*, K+-ATPase NKAIN1-4/Na, K-pumpAction potential and ion transport Fast response cell