Innervation of the heart
This study unit will help you to:
- Learn about the nervous supply of the heart muscle.
- Distinguish between the sympathetic and parasympathetic supply to the heart.
- Understand the components and function of the conduction system of the heart.
The heart receives intrinsic and extrinsic innervation, which allows it to continue to beat independently, even if its nerve supply is disrupted. The intrinsic conducting system initiates and controls the contractions of the heart. The contractions are regulated by an extrinsic regulatory system which consists of autonomic nerve fibers that originate from a network of nerves also known as the cardiac plexus.
The cardiac plexus is formed of both sympathetic and parasympathetic nerve fibers as well as visceral afferent fibers conveying reflexive and nociceptive fibers from the heart. It is located on the anterior surface of the trachea and along the posterior surface of the ascending aorta and pulmonary trunk. The sympathetic innervation to the heart comes from the sympathetic trunk, while the parasympathetic innervation originates from the vagus nerve (CN X). The cardiac plexus is responsible for influencing heart rate, cardiac output, and contraction force of the heart.
This video tutorial will provide you with an overview of the innervation of the heart muscle.
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Take a closer look at the innervation of the heart in the gallery below.
Now you can study each structure of the conduction system of the heart in more detail with our second image gallery:
|Sympathetic (efferent fibers
Superior, middle, inferior cervical and thoracic cardiac nerves (from superior, middle and inferior cervical and upper thoracic paravertebral ganglia)
Function: increase heart rate, increasing force of contraction of myocardium, increasing blood flow in coronary vessels
|Parasympathetic (efferent) fibers
Cervical and thoracic cardiac branches of vagus nerves
Function: reduce heart rate, reduce force of contraction of myocardium, vasoconstriction of aa. coronariae
Afferents return via both sympathetic and parasympathetic pathways
Cervical and thoracic cardiac branches of vagus nerves: feedback on blood pressure and blood chemistry
Cervical and thoracic cardiac nerves: feedback on pain sensation
|Conduction system of the heart
Sinuatrial (SA) node
Atrioventricular (AV) node
Right and left branches of the bundle of His
Subendocardial Purkinje fibers