Module 7: Figure ventricular cell Ca2+ blink
Ventricular cell sparklets, sparks and blinks.
This figure illustrates the organization of a junctional zone with the L-type Ca2+ channels in the T-tubule facing the type 2 ryanodine receptors (RYR2s) in the sarcoplasmic reticulum (SR). The top diagram shows how opening of one of the L-type channels forms a sparklet, which acts within a limited domain to activate a few RYR2s to trigger a spark (bottom diagram). The release of Ca2+ to form the spark depletes Ca2+ within the SR lumen, resulting in a blink. It is this depletion of luminal Ca2+ that may inactivate the RYR2s.