Cardiac Sympathetic Supply — FRCA Primary MCQ
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Correct answer: A — T1–T5
The correct answer is A. Preganglionic cardiac sympathetic neurons are located principally in the intermediolateral cell columns of the upper four or five thoracic spinal cord segments, conventionally described as T1–T5. Their axons leave through the anterior roots and white rami communicantes, then ascend or pass within the sympathetic trunk to synapse in cervical and upper thoracic ganglia. Postganglionic cardiac nerves then reach the cardiac plexus; noradrenaline acting predominantly at β1-adrenoceptors increases heart rate, conduction and contractility. C3–C5 supplies the diaphragm through the phrenic nerve, while S2–S4 is the sacral parasympathetic outflow. Lumbar and lower thoracic segments predominantly contribute sympathetic supply to abdominal and pelvic targets rather than the heart.
Reference: Zandstra TE et al. Asymmetry and Heterogeneity: Part and Parcel in Cardiac Autonomic Innervation and Function. Frontiers in Physiology. 2021;12:665298. Figure 1 and accompanying text. https://pubmed.ncbi.nlm.nih.gov/34603069/