Editing Cardiac action potential (section)

===Calcium channels===
There are two [[Voltage-dependent calcium channel|voltage-gated calcium channels]] within cardiac muscle: [[L-type calcium channel]]s ('L' for Long-lasting) and [[T-type calcium channel]]s ('T' for Transient, i.e. short). L-type channels are more common and are most densely populated within the [[T-tubule]] membrane of ventricular cells, whereas the T-type channels are found mainly within [[Atrium (heart)|atrial]] and [[Cardiac pacemaker|pacemaker cells]], but still to a lesser degree than L-type channels.{{cn|date=April 2024}}

These channels respond to voltage changes across the membrane differently: L-type channels are activated by more positive membrane potentials, take longer to open and remain open longer than T-type channels. This means that the T-type channels contribute more to depolarization (phase 0) whereas L-type channels contribute to the plateau (phase 2).<ref>{{Cite journal |last=Nargeot |first=J. |date=2000-03-31 |title=A tale of two (Calcium) channels |journal=Circulation Research |volume=86 |issue=6 |pages=613–615 |doi=10.1161/01.res.86.6.613 |issn=0009-7330 |pmid=10746994 |doi-access=free}}</ref>