Module 6: Figure Ca2+ oscillation model
A model to explain agonist-dependent Ca2+ oscillations.
The emphasis of this model is that oscillations depend upon the accumulation of Ca2+ within the lumen of the endoplasmic reticulum (ER), which then sensitizes the inositol 1,4,5-trisphosphate (InsP3) receptors to initiate each spike. The site sensitive to luminal Ca2+ is located close to the Ca2+ gate (Module 3: Figure InsP3R activation). Oscillation frequency is thus determined by the rate at which the lumen is loaded with Ca2+, which in turn is determined by the agonist-dependent rate of Ca2+ entry across the plasma membrane. The sequences of events that occur during a typical oscillatory cycle are described in more detail in the text. An animated version of this figure is available.