Region- and condition-dependence of the membrane and Ca2+ clocks in the sinus node.

The results presented by Shinohara et al(1) suggests that both the membrane clock and the Ca(2+) clock contribute to sinus node automaticity. Which is dominant depends on the region within the sinus node and the condition of the SNS. When you change the way you look at things, the things you look at change. This new hypothesis is very attractive, because it combines the membrane and Ca(2+) clocks. In fact, supporting data have been reported by the same parties.(11,12) Supportive studies by others are warranted.