The extrinsic cardiac nervous system
The extrinsic part of cardiac nervous system includes theĀ ganglia and nerves en route to the heart. A ganglion is a cluster of neuronal cell bodies outside the brain (1). In the ANS, while efferent axons from the central nervous system to the ganglion are known as preganglionic nerve fibers, efferent axons from the ganglion to the effector organ are called postganglionic nerve fibers (1). Although ganglia of the sympathetic division are located within the sympathetic chain or paravertebral ganglia, ganglia of the parasympathetic division which are called as either the intramural or the intrinsic ones are distributed mainly within the epicardial area (3, 17, 18) (Figure 1). Thus, parasympathetic postganglionic fibers tend to be shorter than sympathetic ones. All extracardiac nerves access the epicardial neural plexus as extensions of the extrinsic cardiac plexuses.