What did Ivan Pavlov discover about nerves that control the heartbeat?

Through his research on cardiac physiology between 1888 and 1890, Ivan Pavlov made significant contributions to our understanding of how the nervous system regulates the heart.

By performing careful dissections of the fine cardiac nerves, Pavlov demonstrated that the strength of the heartbeat is controlled by nerves originating from the cardiac plexus. Furthermore, by stimulating the severed ends of the cervical nerves, he was able to observe and document the specific effects that the right and left vagus nerves have on heart function. These early studies in circulatory system physiology laid a foundation for his later, more widely recognized work on digestion and conditioned reflexes.12