The ventricles\u2019 sympathetic innervation originates from which spinal levels?

The ventricles\u2019 sympathetic innervation originates from which spinal levels?

• A. T1-T2
• B. T3-T4
• C. T5-T6
• D. C8-T1

Answer: (A)

Sympathetic input to the heart comes from the upper part of the thoracic spinal cord. Preganglionic neurons in the intermediolateral cell columns of these upper thoracic levels send fibers into the sympathetic chain and then out to the heart via the cardiac plexus. The ventricular myocardium is primarily innervated by postganglionic fibers that originate from the first two thoracic segments, traveling with the cardiopulmonary and thoracic cardiac nerves to reach the ventricles. Higher thoracic levels contribute less directly, and levels outside the upper thorax (such as C8-T1) are more involved with other regions like the neck and upper limb. Therefore, T1-T2 provides the main sympathetic innervation to the ventricles.

Sympathetic input to the heart comes from the upper part of the thoracic spinal cord. Preganglionic neurons in the intermediolateral cell columns of these upper thoracic levels send fibers into the sympathetic chain and then out to the heart via the cardiac plexus. The ventricular myocardium is primarily innervated by postganglionic fibers that originate from the first two thoracic segments, traveling with the cardiopulmonary and thoracic cardiac nerves to reach the ventricles. Higher thoracic levels contribute less directly, and levels outside the upper thorax (such as C8-T1) are more involved with other regions like the neck and upper limb. Therefore, T1-T2 provides the main sympathetic innervation to the ventricles.