Thoracic Cardiac Nerves

Origin

The thoracic cardiac nerves originate at the second through fourth (or fifth) thoracic ganglia of the sympathetic trunk. They are the axons of the postganglionic sympathetic neurons found in these ganglia. In cases where there is no cervicothoracic ganglion, a thoracic cardiac branch arises from the first thoracic ganglia of the sympathetic trunk.

Course

The thoracic cardiac nerves emerge from the medial border of the ganglia and run roughly segmentally near the corresponding posterior intercostal arteries to enter the deep cardiac plexus. Fibers from the upper thoracic cardiac nerves can merge with the inferior cervical cardiac nerve or the inferior cervical vagal cardiac branches prior to entering the deep cardiac plexus (Netter, 2011, De Gama et al., 2012, Kuntz and Morehouse, 1930).

Branches

The thoracic cardiac nerves contribute to the deep cardiac plexus.

Supplied Structures & Function

The thoracic cardiac nerves carry both sympathetic efferent fibers and visceral afferent fibers.

Sympathetic efferent fibers supply the heart, and when stimulated, increase heart rate, cardiac impulse conduction, and the force of myocardial contraction, as well as dilate coronary arteries. Visceral afferent fibers from the heart, when stimulated, convey pain sensations via the thoracic cardiac nerves towards the thoracic spinal cord.

List of Clinical Correlates

—Tachycardia

—Referred pain

References

De Gama, B. Z., Lazarus, L., Partab, P. and Satyapal, K. S. (2012) 'The Sympathetic and Parasympathetic Contributions to the Cardiac Plexus: a Fetal Study', International Journal of Morphology, 30, pp. 1569-1576.

Kuntz, A. and Morehouse, A. (1930) 'Thoracic sympathetic cardiac nerves in man: Their relation to cervical sympathetic ganglionectomy', Archives of Surgery, 20(4), pp. 607-613.

Netter, F. H. (2011) Atlas of Human Anatomy. Netter Basic Science Series: Saunders/Elsevier.