Module 7: Figure atrial Ca2+ domains
Modulation of atrial cell contractility by manipulating Ca2+ microdomains.
A. Organization of the junctional sarcoplasmic reticulum (SR) and non-junctional SR separated by the mitochondrial firewall. B. Under control conditions, depolarization (yellow arrows) triggers Ca2+ sparks in the junctional SR that fail to spread to the non-junctional SR, and this results in a small Ca2+ transient. C. In the presence of either isoproterenol or endothelin-1, the initial spark is larger and is able to breach the firewall to ignite the non-junctional type 2 ryanodine receptors (RYR2s) to set up a Ca2+ wave to give a much larger global signal that is responsible for the inotropic response. (Information for this figure was derived from Mackenzie et al. 2004.)