sentences:  The funny current is a mixed sodium–potassium current that activates upon hyperpolarization at voltages in the diastolic range (normally from −60/−70 mV to −40 mV).When, at the end of a sinoatrial action potential, the membrane repolarizes below the If threshold (about −40/−50 mV), the funny current is activated and supplies inward current, which is responsible for starting the diastolic depolarization phase (DD); by this mechanism, the funny current controls the rate of spontaneous activity of sinoatrial myocytes, and thus the cardiac rate.Another unusual feature of If is its dual activation by voltage and by cyclic nucleotides.