The T-type calcium channel (hCav3.2) is a type of voltage-dependent calcium channel, the α1 subunit determines most of the channel's properties. The T-type calcium channel is one of the components that produce the pacemaker potential in the SA node of the heart. T-type calcium channel blockers are used primarily as antiepileptics. Two voltage-dependent calcium channels play critical roles in the physiology of cardiac muscle: L-type calcium channel ('L' for Long-lasting) and T-type calcium channels ('T' for Transient) voltage-gated calcium channels. L-type channels are important in sustaining an action potential, while T-type channels are important in initiating them.