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The heart is innervated by a network of nerves called the cardiac plexus, which is composed of sympathetic and parasympathetic fibres from the autonomic branch of the peripheral nervous system. This network of nerves is responsible for the functioning of the heart, including heart rate, cardiac output, and contraction forces. The sympathetic nervous system controls heart function during stress, while the parasympathetic system helps to decrease heart rate. The cardiac plexus receives contributions from the right and left vagus nerves, as well as the sympathetic trunk, and is split into two parts: the superficial part, located below the arch of the aorta, and the deep part, between the arch of the aorta and the bifurcation of the trachea.
| Characteristics | Values |
|---|---|
| Definition | The innervation of the heart refers to the network of nerves responsible for the functioning of the heart. |
| Innervated by | Sympathetic and parasympathetic fibres from the autonomic branch of the peripheral nervous system. |
| Network of nerves | The cardiac plexus. |
| Location | The cardiac plexus is split into two parts: the superficial part is located below the arch of the aorta and between the arch and the pulmonary trunk; the deep part lies between the arch of the aorta and the bifurcation of the trachea. |
| Function | Influences heart rate, cardiac output, and contraction forces of the heart. |
| Composition | 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. |
| Injury | Injury to the cardiac plexus or its contributories can impair the function of the heart. |
| Neurotransmitters | Norepinephrine, acetylcholine, nitric oxide, vasoactive intestinal peptide. |
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What You'll Learn
- The cardiac plexus is a network of nerves including sympathetic and parasympathetic systems
- The sympathetic nervous system controls heart function during stress
- The vagus nerve reduces the heart rate by releasing acetylcholine
- Injury to the cardiac plexus can impair the function of the heart
- Neural remodeling in the autonomic nervous system contributes to sudden cardiac death
The cardiac plexus is a network of nerves including sympathetic and parasympathetic systems
The cardiac plexus is a network of nerves that includes sympathetic and parasympathetic systems. It is a crucial component of the human body, responsible for the functioning of the heart. The cardiac plexus is formed by the joining of cardiac branches derived from both the sympathetic and parasympathetic nervous systems.
The sympathetic nervous system controls heart function during stress. It originates from the cervical ganglia and T1-T4 or T5, with fibres arising from the upper segments of the thoracic spinal cord. These fibres reach the cardiac plexus via cardiac nerves, and their preganglionic fibres branch from the upper thoracic spinal cord, synapsing in the lower cervical and upper thoracic ganglia. The sympathetic component of the cardiac plexus is responsible for increasing heart rate.
On the other hand, the parasympathetic nervous system, also known as the vagal nervous system, plays a crucial role in regulating various involuntary bodily functions. It provides the parasympathetic innervation of the heart, allowing for a decrease in heart rate. The parasympathetic portions of the cardiac plexus receive contributions from the vagus nerve, which is often referred to as the tenth cranial nerve (CN X). The preganglionic fibres of the vagus nerve branch off and reach the heart, entering the cardiac plexus by synapsing with ganglia within the plexus and the walls of the atria. The right vagus nerve primarily innervates the SA node, while the left vagus nerve has a more substantial effect on the AV node.
The cardiac plexus is divided into two parts: the superficial part and the deep part. The superficial part is located beneath the aortic arch and between the arch and the pulmonary trunk, while the deep part is situated between the arch of the aorta and the bifurcation of the trachea. Small mixed fibres, containing both sympathetic and parasympathetic fibres, branch off the cardiac plexus to supply various structures, including the conduction system of the heart, the coronary vasculature, and the myocardium of the atria and ventricles.
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The sympathetic nervous system controls heart function during stress
The human 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 is composed of fibres from the sympathetic trunk, arising from the upper segments of the thoracic spinal cord.
The sympathetic nervous system is best known for its role in responding to dangerous or stressful situations. In these situations, the sympathetic nervous system activates to speed up the heart rate, delivering more blood to areas of the body that need more oxygen or other responses to help get out of danger. This is often referred to as the "'fight-or-flight' response.
The parasympathetic nervous system, on the other hand, helps to control the body's response during times of rest. It lowers the heart rate and the pumping force of the heart, increases the rate of digestion, and relaxes the muscles that help control urination and defecation. The parasympathetic nervous system also manages sexual functions, including arousal and lubrication.
The sympathetic and parasympathetic nervous systems work together to regulate heart rate, breathing, and stress levels in the body. They have opposite but complementary roles, with the sympathetic nervous system carrying signals that put the body's systems on alert, and the parasympathetic carrying signals that return those systems to their standard activity levels.
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The vagus nerve reduces the heart rate by releasing acetylcholine
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. The cardiac plexus is a network of nerves that includes both the sympathetic and parasympathetic systems. It receives contributions from the right and left vagus nerves, as well as the sympathetic trunk.
The vagus nerve is a key part of the parasympathetic nervous system. The vagus nerve reduces the heart rate by releasing acetylcholine at synapses within cardiac ganglia situated around the heart. This neurotransmitter binds to muscarinic receptors, leading to a decreased heart rate and a reduced force of contraction. This is known as "accentuated antagonism". The right vagus nerve primarily innervates the sinoatrial node (SA node), while the left vagus nerve innervates the atrioventricular node (AVN). However, there can be significant overlap in the anatomic distribution of the two nerves.
The vagus nerve also plays a role in regulating arrhythmogenesis and protecting against ventricular fibrillation. Vagus nerve stimulation (VNS) has been shown to have antiepileptic properties and is currently being investigated as a treatment for inflammatory bowel disease (IBD) and rheumatoid arthritis (RA). VNS uses electrical impulses to stimulate the left vagus nerve, sending mild, painless electrical signals through the nerve to the brain.
Damage to the vagus nerves can affect the ability to decrease the heart rate, leading to tachycardia. Vagus nerve conditions can cause a range of symptoms, including gastroparesis, acid reflux, abdominal pain, bloating, dizziness or fainting, and loss of appetite.
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Injury to the cardiac plexus can impair the function of the heart
The cardiac plexus is a network of nerves located around the base of the heart, formed by cardiac sympathetic nerves and the cardiac branches of the vagus nerve. It is responsible for influencing heart rate, cardiac output, and contraction forces of the heart. 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 the sympathetic trunk.
The cardiac plexus is split into two parts: the superficial part and the deep part. The superficial part is located below the arch of the aorta, between the arch and the pulmonary trunk. 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 the conduction system of the heart, the coronary vasculature, the myocardium (muscle) of the atria and ventricles, the vagus nerve, and the nervus vagus.
Injury to the cardiac plexus or any of its contributories can impair the function of the heart. Damage to the vagus nerves, which provide parasympathetic innervation to the heart, will affect the ability to decrease the heart rate, leading to tachycardia. Similarly, damage to the sympathetic fibres contributing to the cardiac plexus can reduce the ability to increase heart rate, causing bradycardia. The pain-conducting sympathetic afferents transmit pain sensations, which can be detected at a cellular level in the event of tissue damage to the heart, such as cardiac ischemia and myocardial infarction.
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Neural remodeling in the autonomic nervous system contributes to sudden cardiac death
The heart is innervated by sympathetic and parasympathetic fibres from the autonomic branch of the peripheral nervous system. This network of nerves, known as the cardiac plexus, plays a crucial role in regulating heart function, including heart rate, cardiac output, and contraction forces.
Neural remodeling in the autonomic nervous system has been identified as a contributing factor to sudden cardiac death. This remodeling occurs at multiple levels, including the myocardium, intrinsic cardiac ganglia, extracardiac intrathoracic sympathetic ganglia, extrathoracic ganglia, spinal cord, brainstem, and higher centres such as the cortex. Heart disease, for instance, causes neural remodeling at these various levels, predisposing individuals to malignant ventricular arrhythmias.
The process of neural remodeling involves a decrease in parasympathetic input and heterogeneous sympathetic denervation. This imbalance between the sympathetic and parasympathetic branches of the autonomic nervous system can lead to arrhythmias. Specifically, a reduction in parasympathetic input can impair the ability to decrease heart rate, resulting in tachycardia. On the other hand, damage to sympathetic fibres can hinder the ability to increase heart rate, causing bradycardia.
Additionally, neural remodeling can lead to regional nerve sprouting, particularly in the left ventricle, which, when combined with denervation and electrical remodeling due to heart failure, creates favourable conditions for ventricular tachycardia, fibrillation, and sudden cardiac death. Furthermore, over-expression of certain signaling molecules, such as NGF, can decrease the density of specific potassium currents, contributing to arrhythmia susceptibility.
Understanding the complex dynamics of this neural remodeling is essential for developing therapeutic strategies to address sudden cardiac death. These treatments aim to restore the balance between the sympathetic and parasympathetic branches of the autonomic nervous system, thereby mitigating the risk of fatal arrhythmias.
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Frequently asked questions
Cardiac muscle innervation 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 the sympathetic trunk. These nerves influence heart rate, cardiac output, and contraction forces of the heart.
Injury to the cardiac plexus or its contributories can impair the function of the heart. Damage to the vagus nerves will affect the ability to decrease the heart rate, leading to tachycardia. Similarly, damage to the sympathetic fibres can reduce the ability to increase heart rate, causing bradycardia.
