The nerve supply to the heart is categorized as:

• Parasympathetic
• Sympathetic

Select either side of Fig 1 to view the various functions of each nervous system.

The nerve supply to the heart is categorized as:

• Parasympathetic

The vagus and recurrent laryngeal nerves send branches via the deep and superficial cardiac plexuses.

Post-ganglionic fibres pass to the S-A and A-V nodes, with minimal distribution to the ventricles. Vagal stimulation reduces the rate (and force) of contraction and constricts the coronary arteries.

The vagus nerves carry afferent fibres concerned with cardiac reflexes.

• Sympathetic

Select either side of Fig 1 to view the various functions of each nervous system.

The nerve supply to the heart is categorized as:

• Parasympathetic
• Sympathetic

The sympathetic supply originates from the lateral horns of the spinal cord (T1-4). Post-ganglionic fibres arise from the three cervical ganglia and upper thoracic sympathetic ganglia.

Sympathetic stimulation increases the rate and force of contraction and dilates the coronary arteries.

Note: Pain fibres travel with the sympathetic nerves which join the spinal nerves to reach the spinal cord. The association between spinal nerves and the pain fibres may explain why cardiac pain may be referred to the arm or neck.

The autonomic nervous system is covered in: Introduction to Anaesthesia/Basic Science/Physiology Essentials/Autonomic Nervous System.

Select either side of Fig 1 to view the various functions of each nervous system.