The strongest cardiac nerve is the cardiac cervical median nerve. Its origin is in the middle cervical ganglion, and it is involved in the control of cardiac function. Drugs and medications that affect the sympathetic nervous system (sympathomimetics and sympatholytics) can affect cardiac function via the cervical cardiac nerve and the other cardiac nerves.
What is the cardiac cervical median nerve?
There are three cardiac nerves in the chest of humans; the cardiac cervical nerve medius is the strongest of them. The other two are the superior cardiac nerve and the inferior cardiac nerve. They belong to the sympathetic nervous system, which primarily exerts a stimulating influence on the human body, enabling it to temporarily perform greater feats (ergotropy). The complementary system is represented by the parasympathetic nervous system, which mainly controls sedative processes and stimulates digestion. With the enteric nervous system, the intestine also has a specific information network. Both the sympathetic and the parasympathetic and enteric nervous systems belong to the autonomic nervous system. Humans cannot influence it directly or at will; its control emanates primarily from the brainstem, the formate reticularis, and the hypothalamus.
Anatomy and structure
The heart is usually located slightly displaced to the left in the human body; however, exceptions are possible. Therefore, the median cardiac nerve also runs differently in the two halves of the body. On the left side, it passes from the neck between two major blood vessels: Carotid artery (Arteria carotis communis) and Subclavian artery (Arteria subclavia). Signals from the cardiac nerve continue into the cardiac plexus, which is located at the base of the heart and consists of a superficial and a deep portion. The cardiac plexus also receives nerve impulses from the right cervical median nerve. In this half of the body, the nerve travels along behind the carotid artery and further behind or in front of the subclavian artery before continuing downward parallel to the trachea. In its anatomical course through the thorax, the median cardiac nerve is connected to both the superior cardiac nerve, the superior cardiac nerve, and the retrograde laryngeal nerve (recurrent laryngeal nerve). The cardiacus cervicalis medius nerve includes the cervical medium ganglion, which contains the neuronal cell bodies (somata) of the neurons.
Function and Tasks
Signals from the cardiac nerves converge in the carotid plexus, with the deep part of the cardiac plexus being instrumental in the function of the organ. The sympathetic activation that the heart receives from the three cardiac nerves affects the heartbeat, the contraction and relaxation of cardiac muscle fibers, conduction of excitation, and threshold of stimulation. Information reaches the cells of the cervical median cardiac nerve via dendrites; in this case, the stimulus originates from the preceding (preganglionic) cell. The cell bodies of the neurons are located in the cervical medium ganglion. Their stimulation causes ion channels in the cell membrane to open and shift the electrical charge: The cell depolarizes and generates a weak electrical charge that travels as an action potential across the nerve fiber (axon) of the respective cell. The axons of these cells collectively form the nerve and, if necessary, unite with fibers from other cells and other nerve tracts. When switching from one neuron to another, the signal crosses a junction (synapse) with the help of chemical messengers or neurotransmitters formed by the cell in the terminal nodules. The main neurotransmitters of the sympathetic nervous system are acetylcholine and norepinephrine.
Diseases
Damage to the cervical median cardiac nerve potentially affects cardiac function. It is the strongest cardiac nerve and, along with two other sympathetic nerves, affects the deep cardiac plexus, which controls the activity of the vital organ. Drugs and medications that act on the sympathetic nervous system as a whole also show their effects on the cardiac cervical nerve medius and often cause cardiovascular effects. Medicine distinguishes between two groups of substances: sympathomimetics and sympatholytics.Sympathomimetics are drugs or other substances that increase the activity of the sympathetic nervous system. The substances either act directly by mimicking the action of the neurotransmitter acetylcholine and exerting the same effect at the receptors of the cells, or they have an indirect effect. Indirect sympathomimetics also include certain drugs such as cocaine and amphetamines. They inhibit the breakdown of acetylcholine in the synaptic cleft. This allows the neurotransmitter to occupy the receptors longer and trigger a stronger nerve signal. Typical physiological symptoms of cocaine use are accordingly increased blood pressure and pulse, increased respiratory rate, cardiac arrhythmia, lack of perception of thirst and hunger, and disturbed sleep-wake rhythm. The risk of heart attacks and bursting cerebral blood vessels is significantly increased. Physical dependence leads to withdrawal symptoms when the addict stops using the substance. The physical withdrawal symptoms result in part from the body being undersupplied with neurotransmitters without the drug, as it responds more weakly to compensate for the repeated overstimulation of the nervous system. This effect is reversible, however; potential complications of withdrawal require medical monitoring in many cases. Not all sympathomimetics, however, are drugs or addictive at any dose. It is not an increased but a decreased effect of the sympathetic nervous system that sympatholytics trigger. They can also interfere directly or indirectly with neuronal information processing. One example of sympatholytics is alpha blockers, which are used to treat cardiovascular conditions such as elevated blood pressure.
