described herein is a cardiac pacer pulse generator and lead combination in which sinus node cell tissue is harvested or cultured and appropriately affixed to the distal end of the pacing lead to generate electrical depolarization signals whose rate changes with blood - oxygen levels and hormonal activity . the lead includes a sensing electrode for picking up these depolarization signals and applying them to the rate adaptive pacemaker . the pacemaker then functions to produce heart tissue stimulating pulses at a rate dictated by the body &# 39 ; s physiologic demand .