Physiology S.A. node acts as a pacemaker of the hea because of the fact that it: A Is capable of generating impulses spontaneously B Has rich sympathetic innervations. C Has poor cholinergic innervations D Generates impulses at the highest rate. 💡 Explanation S.A. node acts as a pacemaker of the hea because of the fact that it: ✓ Correct Answer: D. Generates impulses at the highest rate.