Figure 1.

Schematic depiction of the central role of the BK channel in regulation of myogenic tone in bladder smooth muscle. As shown, detrusor smooth muscle exhibits spontaneous myogenic contractile activity (spikes) associated with depolarizations. The depolarizations are associated with Ca²⁺ influx via voltage-dependent calcium channels (VDCCs). Ca²⁺-induced Ca²⁺ release from the sarcoplasmic reticulum activates BK channels via “sparks,” but BK channels are also activated via more global increases in intracellular calcium, and eventually the cell is repolarized. The repolarization closes (temporarily) the VDCC, and spike activity is reduced.