Fig. 4.

Effects of physiological levels of baseline stretch on isolated sinoatrial node (SAN) beating rate. Floating microelectrode recordings of transmembrane potential in cat isolated SAN, showing a stretch-induced shift of the maximum diastolic potential towards less negative values, resulting in A restoration of regular rhythm in a SAN with irregular activity at slack length or B initiation of spontaneous excitation in a previously quiescent SAN. In both examples, tissue length was increased by ~40% from slack, with periods of stretch indicated by the lower horizontal lines. From Lange et al. (1966)