Hypothesis of how changes to the affected region cause a sustained perturbation yielding a trigged point. Conceptual phase plane diagrams for intracellular [Ca2+] and [ROS]. (a) The [ROS] nullcline (red) intersects the [Ca2+] nullcline (blue) at the steady state value for resting [Ca2+] and [ROS] (black dot). (b) With the changes that occur with microtubule proliferation and reduction in the ability of the myocyte to remove ROS, the [ROS] nullcline shifts to the right higher [ROS] for a given level of [Ca2+] resulting in a higher steady-state [ROS] and [Ca2+].
