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Innervation of the heart

Recommended video: Innervation of the heart [05:29]
Autonomic innervation of the heart seen from the anterior view of open thorax.

The innervation of the heart refers to the network of nerves that are responsible for the functioning of the heart. The heart is innervated by sympathetic and parasympathetic fibres from the autonomic branch of the peripheral nervous system.

The network of nerves supplying the heart is called the cardiac plexus. It receives contributions from the right and left vagus nerves, as well as contributions from the sympathetic trunk. These are responsible for influencing heart rate, cardiac output, and contraction forces of the heart.

Key facts about the innervation of the heart
Parasympathetic efferent fibers Vagus nerve
Function: reducing the heart rate, reducing the force of contraction of the heart, vasoconstriction of the coronary arteries
Sympathetic efferent fibers Cardiac nerves from the lower cervical and upper thoracic ganglia
Function: increasing heart rate, increasing the force of contraction of the myocardium
Afferent parasympathetic fibers Vagal cardiac nerves
Function: feedback on blood pressure
Afferent sympathetic fibers Afferents to upper thoracic and lower cervical ganglia
Function: feedback on blood pressure, pain sensation
Clinical relations Cardiac plexus injury, referred pain

This article will discuss the innervation of the heart.

  1. Cardiac plexus
    1. Parasympathetic innervation
    2. Sympathetic innervation
    3. Cardiac afferents
  2. Clinical notes
    1. Cardiac plexus injury
    2. Referred pain
  3. Sources
+ Show all

Cardiac plexus

The cardiac plexus is a network of nerves including both the sympathetic and parasympathetic systems. It is split into two parts. The superficial part is located below the arch of the aorta, and between the arch and the pulmonary trunk.

Have you already mastered the basic anatomy of the heart? Test yourself now with our handy diagrams, quizzes and worksheets of the heart. 

The deep part lies between the arch of the aorta and the bifurcation of the trachea. Small mixed fibres (containing both sympathetic and parasympathetic fibres) branch off of the cardiac plexus and supply: 

Parasympathetic innervation

The parasympathetic portions of the cardiac plexus receive contributions from the vagus nerve only. The preganglionic fibres, branching from the right and left vagus nerves, reach the heart. They enter the cardiac plexus by synapsing with ganglia within this plexus and walls of the atria.

Parasympathetic innervation is responsible for:

  • reducing the heart rate
  • reducing the force of contraction of the heart
  • vasoconstriction (narrowing) of the coronary arteries

Sympathetic innervation

The sympathetic part of the cardiac plexus is composed of fibres from the sympathetic trunk, arising from the upper segments of the thoracic spinal cord. Fibres from the sympathetic trunk reach the cardiac plexus via cardiac nerves. The preganglionic fibres branch from the upper thoracic spinal cord and synapse in the lower cervical and upper thoracic ganglia. Postganglionic fibres extend from the ganglia to the cardiac plexus. 

Sympathetic nerves are responsible for:

  • increasing heart rate
  • increasing the force of contraction of the myocardium
  • the ‘fight or flight’ response, causing our heart to beat faster.

Solidify your knowledge on the innervation of the heart with the following quiz!

Cardiac afferents

Afferent fibres also form part of the cardiac plexus. They return to the central nervous system via both the sympathetic cardiac branches and the cardiac nerves from the right and left vagus nerves.

The afferents passing through the cardiac branches of vagus nerves provide feedback on blood pressure and blood chemistry.

In the sympathetic branch, the visceral afferents return to the upper thoracic and lower cervical ganglia. The fibres entering the upper cervical region are typically redirected down towards the upper thoracic portions of the sympathetic trunk, where they reenter the upper thoracic regions of the thoracic spinal cord, joining afferents from the thoracic ganglia. Sympathetic afferents relay pain sensation from the heart.

The following resources will help you to master the innervation of the heart and cement your knowledge.

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