Phase 3 - rapid repolarisation

Stable Identifier
R-HSA-5576890
Type
Pathway
Species
Homo sapiens
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In phase 3 (the "rapid repolarisation" phase), the L-type Ca2+ channels close, while the slow delayed rectifier (IKs) K+ channels remain open as more K+ leak channels open. This ensures a net outward positive current, corresponding to negative change in membrane potential, thus allowing more types of K+ channels to open. These are primarily the rapid delayed rectifier K+ channels (IKr) and the inwardly rectifying K+ current, IK1 (Kir). This net outward, positive current (equal to loss of positive charge from the cell) causes the cell to repolarize. The primary delayed rectifier K+ currents (IKs and IKr) are generated by K+ efflux mediated by potassium voltage-gated channel subfamily KQT member 1 (KCNQ1 aka Kv7.1) and potassium voltage-gated channel subfamily H member 2 (KCNH2 aka HERG) channels respectively (Park & Fishman 2011, Grant 2009). Specific to the atria, an ultra-rapidly activating delayed rectifier outward K+ current (IKur) generated primarily by potassium voltage-gated channel subfamily A member 5 (KCNA5) helps to repolarize atrial cells (Wang et al. 1993, Feng et al. 1997).

Literature References
PubMed ID Title Journal Year
19808464 Cardiac ion channels

Grant, AO

Circ Arrhythm Electrophysiol 2009
21357845 The cardiac conduction system

Park, DS, Fishman, GI

Circulation 2011
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