The superior mesenteric ganglion is part of the solar plexus and is located on the superior mesenteric artery in the mid-abdomen. Nerve fibers originating from this ganglion primarily innervate the pancreas, parts of the colon, and the small intestine.
What is mesenteric superior ganglion?
The prevertebral ganglia in the abdomen include the mesenteric ganglion superius. It is associated with the solar plexus or solar plexus. This plexus is a collection point for parasympathetic fibers from the vagus nerve and sympathetic fibers from the greater visceral nerve (splanchnic nerve major) and the lesser visceral nerve (splanchnic nerve minor). The solar plexus lies behind the stomach and brings together nerve cells that regulate digestion. In itself, the mesenteric superficial ganglion belongs to the sympathetic nervous system and, as such, is primarily involved in effects that are stimulating and performance-enhancing on the organism. Medical science also refers to this process as ergotropy.
Anatomy and structure
Nerve pathways entering the ganglion (preganglionic cells) form a node and transmit their neuronal data to other neurons (postganglionic neurons). The postganglionic nerves of the superior mesenteric ganglion form the superior mesenteric plexus. It forms part of a superior nerve plexus. This is the solar plexus, which also consists of fibers from the coeliacal ganglion and fibers from the aorticorenal ganglia. The superior mesenteric plexus runs along the superior mesenteric artery. The blood vessel supplies the ascending, transverse, and descending colon as well as the duodenum, pancreas, and small intestine. Together with the superior mesenteric artery, the superior mesenteric plexus extends to lower parts of the body and eventually reaches the pancreas, small intestine and part of the colon. Some fibers passing through the superior mesenteric ganglion reach the adrenal medulla without first transferring their information to other cells. The adrenal medulla constitutes a sympathetic paraganglion and produces epinephrine and norepinephrine.
Function and tasks
The mesenteric ganglion superius contains nerve cell bodies (somata) whose signals are significant for the function of the digestive system. For this reason, the nerve cell node belongs to the autonomic or vegetative nervous system: humans cannot directly control it at will. Instead, regulation emanates from areas of the brain that are relatively old in developmental history. Despite its highly automated functions, however, the circuitry in the peripheral nervous system is not primitive but very complex. The mesenteric superior ganglion is only one circuit site of many in the course of the splanchnic major and splanchnic minor nerves. Within the ganglion, the switching of neurons takes place with the help of neurotransmitters; acetylcholine represents the most significant of them in the autonomic nervous system. The switched fibers from the mesenteric ganglion superius have three main targets: the pancreas, the small intestine and parts of the colon. The pancreas or pancreas is not only involved in digestion by producing enzymes in its exocrine part that cleave carbohydrates, proteins and fats; the gland also performs hormonal functions. The endocrine pancreas contains specialized cells, each of which synthesizes different hormones: Insulin, glucagon, somatostatin, pancreatic polypeptide, and ghrelin. When appropriately stimulated, the pancreas secretes these hormones directly into the blood. On the small intestine, sympathetic activation has an inhibitory effect; intestinal movements and secretion of secretions are reduced. Conversely, parasympathetic activation by other nerve fibers achieves a digestive effect. This example illustrates how the two subsystems of the autonomic nervous system act as counterparts. The mesenteric ganglion superius also innervates the colon as far as the left colonic flexure. Here, the digestive system extracts water and electrolytes from the digested food pulp. In addition, some nerve fibers from the mesenteric ganglion superius supply parts of the uterus in women.
Diseases
Ganglion blockers, which were once widely used as medications, are now rarely used: The drugs have a very nonspecific effect on the autonomic nervous system, causing numerous side effects in addition to their main effect. Ganglion blockers (also: ganglioplegics) reduce the transmission of nerve signals in the ganglia of the human body or, at the appropriate dose, stop it completely. Organs that rely on information from these nerve ganglia receive no or only weak stimuli in this way and also reduce their activity. One ganglion blocker that is still used in medicine is phenobarbital; doctors use it in part to treat epilepsy to prevent the development of seizures. As a result of impaired signaling in the ganglia, the drug generally has a sedative effect and may cause side effects such as ataxia, sexual dysfunction, drowsiness, dizziness, fatigue, headache and coordination difficulties. Psychological symptoms are also possible after taking phenobarbital. Not every form of epilepsy responds to this agent, and individual causes also influence its effectiveness. The “truth serum” amobarbital is also an example of a ganglion blocker. It is used in legal proceedings to make individuals tell the truth during interrogation. However, both the reliability and the ethical basis for its use are highly controversial. Amobarbital is a barbiturate and is rarely used today as a sedative or sleep aid. Physical dependence on ganglion blockers is possible to some extent; in addition, fatal side effects such as cardiac arrest can occur with overdose. Whether the medical use of a ganglion blocker is beneficial or whether the risks outweigh the benefits depends on the individual case.
