Editing Repolarization (section)

== Repolarization of atria cells ==
Another type of K<sup>+</sup> channel that helps to mediate repolarization in the human [[Atrium (heart)|atria]] is the [[SK channel]], which are K<sup>+</sup> channels which are activated by increases in Ca<sup>2+</sup> concentration. "SK channel" stands for a small conductance calcium activated potassium channel, and the channels are found in the heart. SK channels specifically act in the right atrium of the heart, and have not been found to be functionally important in the ventricles of the human heart. The channels are active during repolarization as well as during the atrial diastole phase when the current undergoes hyperpolarization.<ref name="Skibsbye_2014">{{cite journal | vauthors = Skibsbye L, Poulet C, Diness JG, Bentzen BH, Yuan L, Kappert U, Matschke K, Wettwer E, Ravens U, Grunnet M, Christ T, Jespersen T | display-authors = 6 | title = Small-conductance calcium-activated potassium (SK) channels contribute to action potential repolarization in human atria | journal = Cardiovascular Research | volume = 103 | issue = 1 | pages = 156–67 | date = July 2014 | pmid = 24817686 | doi = 10.1093/cvr/cvu121 | doi-access = free }}</ref> Specifically, these channels are activated when Ca<sup>2+</sup> binds to [[calmodulin]] (CaM) because the N-lobe of CaM interacts with the channel's S4/S5 linker to induce conformational change.<ref name="pmid29724949">{{cite journal | vauthors = Lee CH, MacKinnon R | title = Activation mechanism of a human SK-calmodulin channel complex elucidated by cryo-EM structures | journal = Science | volume = 360 | issue = 6388 | pages = 508–513 | date = May 2018 | pmid = 29724949 | pmc = 6241251 | doi = 10.1126/science.aas9466 | bibcode = 2018Sci...360..508L }}</ref> When these K<sup>+</sup> channels are activated, the K<sup>+</sup> ions rush out of the cell during the peak of its action potential causing the cell to repolarize as the influx of Ca<sup>2+</sup> ions are exceeded by K<sup>+</sup> ions leaving the cell continuously.<ref>{{cite web | first = Scott | last = Goodman | name-list-style = vanc |url= https://www.kumc.edu/AMA-MSS/Study/phys2.htm |work=Physiology Medical Study Guides | title = Cardiovascular |publisher = University of Kansas Department of Physiology |access-date=2019-09-25 }}</ref>