The autonomic nervous system is understood to be the totality of nerve and ganglion cells that autonomously regulate the vital functions of the human organism. Primary diseases of the autonomic nervous system generally occur rarely.
What is the autonomic nervous system?
The autonomic part of the nervous system that controls vital organ functions of the human organism, such as respiration, metabolism, digestion, and blood pressure, without being subject to the will or consciousness of the human being, is called the autonomic nervous system. Depending on the course and function of the nerve fibers, a distinction is made between the sympathetic (sympathetic), parasympathetic (parasympathetic) and enteric nervous systems. While the sympathetic and parasympathetic nervous systems regulate various organ systems in an antagonistic interplay, the enteric nervous system, also called the intestinal nervous system, controls intestinal function and digestion via nerve plexuses located between the muscle layers of the intestinal wall.
Anatomy and structure
The autonomic nervous system is divided into sympathetic, parasympathetic, and enteric nervous systems. The sympathetic nerve fibers originate in the lateral horns of the spinal cord (medulla spinalis) and run in the head, neck, and chest regions via the spinal nerve (spinal nerve) to the right or left truncus sympathicus (border cord), which consists of a ganglionic chain (collection of nerve cells outside the CNS) and is located near the vertebral bodies. From the truncus sympathicus, sympathetic nerve cells extend singly or in combination with spinal nerves to the organs to be specifically innervated. In the abdominal and pelvic regions, the sympathetic fibers are switched to prevertebral ganglia and subsequently form nerve plexuses (plexus) together with parasympathetic fibers, which lead with the blood vessels to the corresponding organs. In addition to the internal organs, the sympathetic nervous system supplies the vessels, smooth muscles, and tear, salivary and sweat glands. The parasympathetic fibers, on the other hand, originate in the brainstem and sacral medulla (spinal cord segments S1 to S5), from where they lead, along with cranial and spinal nerves, to the parasympathetic ganglia, which are located near or within the organs of success. Parasympathetic nerve plexuses are detectable in the stomach, bladder, intestines as well as uterus, among others. The enteric nervous system mainly controls intestinal function via two plexuses (myenteric plexus, submucosal plexus) located between the intestinal muscles, which innervate the entire intestinal musculature.
Functions and tasks
Almost all organs of the human body are innervated by the autonomic nervous system, especially sympathetic and parasympathetic nerve fibers. Here, the sympathetic and parasympathetic nervous systems function as antagonistic counterparts, whose interaction ensures optimal function of the organs in coordination with the specific needs of the organism. While the sympathetic nervous system generally ensures an increase in performance according to the principle of “fight or flight”, the parasympathetic nervous system ensures regular bodily functions at rest as well as physical regeneration and the body’s own reserve build-up. Accordingly, the sympathetic nervous system controls, for example, the increase in frequency and contraction of the heart, while the parasympathetic nervous system causes a reduction in both parameters. Similarly, the interaction of the sympathetic (dilatation) and parasympathetic (constriction) nervous systems regulates the coronary arteries, bronchi, and pupillary function. In addition, sympathetic and parasympathetic nerves are involved in the control of male sex hormones, with sympathetic nerve fibers causing ejaculation and parasympathetic ones causing erection. In addition, sympathetic nerve fibers ensure mild constriction of cerebral vessels as well as skin, mucosal, and visceral vessels. The enteric nervous system controls intestinal muscle peristalsis, gastrointestinal secretion and blood flow, and intestinal immunologic functions in a sympathetic-parasympathetic-dependent manner.
Diseases
In general, primary diseases of the autonomic nervous system may be rarely observed. Trauma may result in impaired water balance and body temperature regulation as direct damage to the hypothalamus, whereas systemic diseases such as diabetes mellitus or cancer affect overall sympathetic nervous function.A well-known clinical picture is the so-called Horner syndrome, which is caused by a failure of the cervical sympathetic nervous system and is characterized by a triad of specific symptoms. Due to the failure of the musculus dilatator pupillae, which is controlled by the sympathetic nervous system, the pupil is constricted (miosis), as a result of an impairment of the sympathetically innervated musculus tarsalis the eyelid hangs down (ptosis) and due to the failure of the musculus orbitalis the eyeball lies lower (enophthalmos). If the enteric nervous system or enteric plexus is affected, bowel function is impaired. Diseases such as Crohn’s disease (chronic inflammation of the intestine), Hirschsprung’s disease (congenital megacolon), and ulcerative colitis (chronic inflammation of the colon) may result. Impairments of the parasympathetic nervous system are particularly associated with sleep disorders. In addition, vegetative disorders can affect blood regulation (blood fluctuations), respiratory regulation (hyperventilation, shortness of breath), vascular regulation (Raynaud’s syndrome), gastrointestinal regulation (irritable bowel, stomach), bladder control (irritable bladder), thermoregulation (sweating or (sweating or freezing), blood sugar control (drop in blood sugar, attacks of weakness), inner ear function (tinnitus, dizziness), pupil motor function (blurred vision), pain regulation (vulvodynia, fibromyalgia syndrome) and immune defense (increased susceptibility to infections). In addition, impairments of the autonomic nervous system generally entail increased sensitivity.
