Your heart cells are all capable
of contracting and causing the
heart to beat. Usually, this job is segregated to specific
cells that most people refer to as the "natrual pacemaker." However, as I said before, ALL heart cells are capable of triggering a contraction. When the electrical system in your heart goes a bit haywire (like a blown fuse or a power surge) then the cells in the heart can react by causing a premature heart beat.