How can hearts beat outside the body? It could be her “little brain.”

Take out a human’s heart and – assuming you store it in precise conditions for transplantation – it can keep beating. How? Well, it could be the organ’s “little brain,” as new research has found that a collection of neurons may play a much more important role in maintaining the heartbeat than previously thought.

This little brain is the so-called intracardiac nervous system, a collection of nerves and ganglia located in the heart tissue. It acts like a local control system that can regulate heart function. However, it was believed that the intracardiac nervous system was a simplified structure that received its commands from the brain. Now new research has revealed that there could be more to the story.

“This ‘little brain’ plays a key role in maintaining and controlling the heartbeat, similar to how the brain regulates rhythmic functions such as locomotion and breathing,” explains study leader Konstantinos Ampatzis, principal investigator and lecturer at the Department of Neuroscience at Karolinska Institutet, Sweden, in a press release.

“We were surprised to see how complex the nervous system in the heart is. A better understanding of this system could lead to new insights into heart disease and help develop new treatments for diseases such as cardiac arrhythmias.”

The research examined the hearts of zebrafish to delve deeper into the role of the intracardiac nervous system, a common animal model in heart research because its heart shares many similarities with ours. This allowed them to map the organization and function of neurons in the heart using single-cell RNA sequencing, anatomical studies and electrophysiological techniques.

They saw that there are several different types of neurons in the heart that perform different functions, including a small group that has the properties of a pacemaker. The groundbreaking study challenges long-held ideas about how the heart beat is maintained and could be a crucial development for future treatments and interventions for cardiovascular disease.

“We will now further investigate how the cardiac brain interacts with the actual brain to regulate cardiac functions under various conditions such as exercise, stress or illness. Our goal is to identify new therapeutic targets by studying how disruptions in the cardiac neural network contribute to various heart diseases.”

The study was published in Nature Communications.