I'm not sure I understand the distinction you're making, and whether the nerves are considered part of the heart there are most definitely nerves into the heart

I'm not sure I understand the distinction you're making, and whether the nerves are considered part of the heart there are most definitely nerves into the heart. From [1], "The vagus nerve directly innervates the sinoatrial node; when activated, it serves to lower the heart rate". This is illustrated here [2], in a diagram from Gray's Anatomy of the Human Body. [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4404375/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4404375/ [2] https://en.wikipedia.org/wiki/Vagus_nerve#/media/File:Gray793.png https://en.wikipedia.org/wiki/Vagus_nerve#/media/File:Gray79...