Cardiac ganglia

Cardiac ganglia refer to accumulation of cell bodies of post-ganglionic parasympathetic neurons which are situated either inside the cardiac plexus or within the heart itself.

Inside the heart, the largest collection of cardiac ganglia are found near the sinoatrial and atrioventricular nodes, while smaller collections are situated on the left atrial surfaces, at the junction of atrial appendage with the atria, at the base of great vessels and base of ventricles. Almost no ganglia are found in the right atria, trunks of great vessels, atrial appendages and ventricular musculature. Also note that most cardiac ganglia are found within the epicardium surrounded by adipose tissue. Few are found within the myocardium, while none within the endocardium or sub-endocardium.

Cardiac ganglia receive parasympathetic innervation via the cardiac branches of the vagus nerve. They contain preganglionic parasympathetic neurons which originate from the dorsal motor nucleus of vagus in the brainstem. They synapse with cell bodies of post-ganglionic neurons within the cardiac ganglia, located inside the cardiac plexus or within the heart. Thereupon, the post-ganglionic neurons project to the sinoatrial and atrioventricular nodes and to the atrial and ventricular musculature. Functionally, the parasympathetic innervation decreases heart rate, reduces force of cardiac contraction and constricts the coronary arteries.

Being mindful of the location of cardiac ganglia is important while undertaking surgical procedures on the heart. Sparing the cardiac regions where ganglia are concentrated could help minimize the risk of cardiac arrhythmias and related complications.