The inferior cardiac cervical nerve is a sympathetic nerve of the autonomic nervous system. It is one of the three sympathetic cardiac nerves used to promote cardiac activity. In autonomic dysfunction, sympathetic cardiac activity can cause symptoms such as palpitations.
What is the inferior cardiac nerve?
The human heart is equipped with three cardiac nerves from the autonomic nervous system that influence the autonomic activity of the heart. In addition to sympathetic pathways, parasympathetic nerve pathways draw to the heart and determine heart rate, force development, excitation process, and excitability threshold. The cardiac nerves correspond to the sympathetic nerve fiber tracts of the heart and extend from the three cervical ganglia to the cardiac plexus at the base of the heart. The inferior cardiac nerve is the cardiac nerve that arises from the inferior cervical ganglion or first thoracic ganglion. Like the other two cardiac nerves, the superior cardiac nerve and the median cardiac nerve, the inferior cardiac nerve carries purely sympathetic fiber tracts that have an excitatory effect on cardiac activity. In contrast, the heart receives attenuation from the parasympathetic fiber tracts.
Anatomy and structure
The inferior cardiac nerve arises from the inferior cervical ganglion. This ganglion corresponds to a collection of nerve cells in the inferior cervical region and is one of the three border cord cervical ganglia. In many individuals, the cervical inferior ganglion is fused with the first thoracic ganglion and then forms what is known as the stellate ganglion. Where the ganglion connects to postganglionic neurons, the individual nerve branches withdraw from the nerve cell body collection to their supply areas. One of these nerve branches is the ramus cardiacus, which forms the inferior cardiac nerve and travels to the cardiac plexus of the heart. To do this, the nerve branch descends caudally from the cluster of nerve cell bodies at the anterior front of the trachea, passing behind the subclavian artery. The sympathetic nerve communicates with the recurrent laryngeal nerve and the median cervical cardiac nerve in its course.
Function and Tasks
The heart of a newborn beats automatically about 120 times per minute. On average, the heart rate of a healthy person at rest is 50 to 100 beats per minute. Unlike other muscles of the body, the heart’s activity escapes voluntary control and is controlled by the autonomic nervous system. The autonomic nervous system consists of the parasympathetic and sympathetic nervous systems. The former has an inhibitory effect, while the sympathetic nervous system has an excitatory effect. With its excitatory mode of action, the sympathetic nervous system plays a role primarily in the body’s stress reactions and prepares the human organism for maximum performance in stressful situations. As one of the three sympathetic cardiac nerves, the inferior cardiac nerve promotes cardiac activity. The autonomic nerve is involved both in the promotion of heart rate (cardiac output) and in the stimulation of force development (cardiac mechanics), excitation process of the excitability threshold. In addition to the sympathetic nervous system, the parasympathetic nervous system also innervates all three automatic centers of the heart. Together, all sympathetic and parasympathetic cardiac nerves of the autonomic nervous system are responsible for cardiac automatism. The ventricular muscles are supplied purely sympathetically. The heartbeat permanently pumps blood into the arterial side of the circulation. The excitation conduction system of the heart triggers cardiac activity, thus distinguishing an electrical from a coordinated mechanical cardiac action. Arterial blood supplies all tissues and organs of the body with nutrients, oxygen and messenger substances. Thus, through its involvement in the excitation of the heart, the inferior cardiac nerve is also involved in the blood supply to tissues and is a correspondingly vital structure of the autonomic nervous system. Under normal physiological conditions, the heart is permanently excited by the sympathetic and parasympathetic nervous systems. The parasympathetic influence predominates in a majority of vertebrates.
Diseases
A disease affecting the conduction of excitation of the heart and, consequently, the activity of the inferior cardiac nerve is autonomic dystonia.This disease of the autonomic nervous system disrupts the course of all automatic bodily functions, such as blood pressure regulation and lung activity, in addition to heart activity. The sympathetic nervous system puts people under tension, accelerates heartbeat and breathing, and triggers a fight-or-flight response throughout the organism. The parasympathetic nervous system is responsible for relaxation processes and regeneration. Both systems play together permanently in a healthy body. A disturbance of this interaction results in vegetative dystonia. The tension ratio can shift in favor of the sympathetic nervous system as well as in favor of the parasympathetic nervous system. In the case of increased sympathetic activity, the three sympathetic cardiac nerves including the inferior cardiac cervical nerve activate the heart to palpitate, so that blood pressure increases. When there is a shift in favor of the parasympathetic nervous system, the parasympathetic nerves of the heart dampen the sympathetic nerve fibers, causing a slowing of cardiac activity associated with low blood pressure levels. In many cases, vegetative dystonia has no clearly identifiable cause and may be related to physical, psychological as well as social circumstances. The pathological acceleration of cardiac activity is also known as tachycardia. Under physical stress, sympathetically mediated cardiac acceleration is a normal response that adjusts cardiac output to meet momentary demands. In contrast, a sympathetically mediated increase in resting heart rate indicates disease. These diseases do not have to lie primarily in the heart, but can also be systemic and thus affect the entire body. Conceivable causes are incipient or manifest infectious diseases, but also psychological tension. The phenomenon of tachycardia due to mental tension is also known as nervous heart disease. Because of the symptoms, sufferers often fear that they are suffering from organic heart disease with a risk of heart attack. This fear can exacerbate sympathetically mediated tachycardia.
