High resolution

Module 2: Figure Ca2+ transient mechanisms

The sequence of ON and OFF reactions during the generation of a typical Ca2+ transient.

The rising phase of the Ca2+ spike results from the activation of Ca2+ entry and release mechanisms (yellow bars), which are then terminated by inactivation processes. Once the ON reactions have been inactivated, a series of OFF reactions operate in a sequential manner to restore Ca2+ to its resting level (blue bars). During the rising phase of the Ca2+ transient, large amounts of Ca2+ are rapidly bound to the Ca2+ buffers (calbindin D-28k and parvalbumin) and are taken up by the mitochondria. The mitochondria and cytosolic buffers help to shape the Ca2+ signal by reducing the impact of the ON reactions. In effect, they enable the cell to generate very fast transients without running the risk of being overwhelmed by Ca2+.