Editing Cardiac action potential (section)

{{short description|Biological process in the heart}}
[[File:Action potential ventr myocyte.gif|thumb|Basic cardiac action potential]]
Unlike the [[action potential]] in [[skeletal muscle|skeletal muscle cells]], the cardiac action potential is not initiated by nervous activity. Instead, it arises from a group of specialized cells known as [[pacemaker cell]]s, that have automatic action potential generation capability. In healthy hearts, these cells form the [[cardiac pacemaker]] and are found in the [[sinoatrial node]] in the right [[atrium (heart)|atrium]]. They produce roughly 60–100 action potentials every minute. The action potential passes along the cell membrane causing the cell to contract, therefore the activity of the sinoatrial node results in a resting heart rate of roughly 60–100 beats per minute. All cardiac muscle cells are electrically linked to one another, by [[intercalated disc]]s which allow the action potential to pass from one cell to the next.<ref name="Zhao">{{Cite journal |last=Zhao |first=G |last2=Qiu |first2=Y |last3=Zhang |first3=HM |last4=Yang |first4=D |date=January 2019 |title=Intercalated discs: cellular adhesion and signaling in heart health and diseases. |journal=Heart Failure Reviews |volume=24 |issue=1 |pages=115–132 |doi=10.1007/s10741-018-9743-7 |pmid=30288656 |s2cid=52919432}}</ref><ref name="pmid24578694">{{Cite journal |vauthors=Kurtenbach S, Kurtenbach S, Zoidl G |date=2014 |title=Gap junction modulation and its implications for heart function |journal=Frontiers in Physiology |volume=5 |pages=82 |doi=10.3389/fphys.2014.00082 |pmc=3936571 |pmid=24578694 |doi-access=free}}</ref> This means that all atrial cells can contract together, and then all ventricular cells.
[[File:Shapes of the cardiac action potential in the heart.svg|thumb|300x300px|Different shapes of the cardiac action potential in various parts of the heart]]
Rate dependence of the action potential is a fundamental property of cardiac cells and alterations can lead to severe cardiac diseases including [[Arrhythmia|cardiac arrhythmia]] and sometimes sudden death.<ref name="pmid25113792">{{Cite journal |vauthors=Soltysinska E, Speerschneider T, Winther SV, Thomsen MB |date=August 2014 |title=Sinoatrial node dysfunction induces cardiac arrhythmias in diabetic mice |journal=Cardiovascular Diabetology |volume=13 |pages=122 |doi=10.1186/s12933-014-0122-y |pmc=4149194 |pmid=25113792 |doi-access=free}}</ref>
Action potential activity within the heart can be recorded to produce an [[electrocardiogram]] (ECG). This is a series of upward and downward spikes (labelled P, Q, R, S and T) that represent the depolarization (voltage becoming more positive) and repolarization (voltage becoming more negative) of the action potential in the [[atrium (heart)|atria]] and [[ventricle (heart)|ventricle]]s.<ref>{{Cite journal |last=Becker Daniel E |year=2006 |title=Fundamentals of Electrocardiography Interpretation |journal=Anesthesia Progress |volume=53 |issue=2 |pages=53–64 |doi=10.2344/0003-3006(2006)53[53:foei]2.0.co;2 |pmc=1614214 |pmid=16863387}}</ref>