High resolution

Module 7: Figure pacemaker Ca2+ sparks

Appearance of Ca2+ sparks in an atrial pacemaker cell.

The measurement of Ca2+ in the top trace illustrates the appearance of small sparks that precede the onset of the large Ca2+ spike that occurs during the action potential. The spatiotemporal plot shown on the bottom provides a visual record of the Ca2+ signals that occur in a region close to the plasma membrane (indicated by the orange line in the inset where the scan was made) during the final period of the pacemaker phase. Note the small Ca2+ sparks that occur before the onset of the large uniform elevation of Ca2+ that occurs when the L-type channels open during the action potential. Reproduced from Hüser, J., Blatter, L.A. and Lipsius, S.L. (2000) Intracellular Ca2+ release contributes to automaticity in cat atrial pacemaker cells. J. Physiol. 524:415–422, with permission from Blackwell Publishing; see Hüser et al. 2000.