Function of the vagus nerve
As already mentioned, the vagus supplies many organs from head to belly. Its function is very specific, depending on which organ is considered. It is the most important representative of the “parasympathetic nervous system“.
This works in the opposite direction to the “sympathetic nervous system“. Roughly speaking, the parasympathetic system is responsible for rest, relaxation and digestion, while the sympathetic system is responsible in terms of developmental history for fighting and escape situations. In the head/neck region, the vagus nerve is responsible for the sensitive and sometimes taste sensation of the pharyngeal mucosa, larynx, glottis, areas of the meninges and parts of the auditory canal.
It also activates the muscles of the throat and especially those of the larynx and glottis, thus enabling both speech and the swallowing process. In the thoracic cavity, the vagus nerve primarily has a calming effect on the lungs and heart. One of its main effects concerns the digestive system. It has digestive effects on the esophagus, stomach, liver, gall bladder, pancreas, small intestine and parts of the large intestine.
Receptor organs of the vagus nerve
The recipient organs of the vagus nerve are located in the chest and abdomen. It supplies e.g. liver, kidneys, spleen and stomach. The point at which the parasympathetic supply from the vagus nerve ends is called the Cannon-Böhm point.
It is located in the middle section of the colon (more precisely: last third of the transverse colon). While the cranial part of the parasympathetic nervous system innervates the tear and salivary glands, some of the eye muscles and all organs of the chest and abdomen up to the Cannon-Böhm point, the sacral part of the parasympathetic nervous system starts at this point and continues the supply further down. It thus innervates the rest of the colon, the bladder and the genitals.
Again, for those interested in details, this is a precise description of the facts: The sacral part of the parasympathetic nervous system originates in the nucleus intermediolateralis and nucleus intermediomedialis of the sacral part of the spinal cord (sacral marrow) and then runs first with the pudendal nerve. It then passes through the plexus hypogastricus inferior (lat. plexus = nerve plexus).Switching to the 2nd neuron is either done here or directly in the wall of the recipient organ.
From this plexus, the parasympathetic fibers run as pelvic nerves (lat. pelvis = pelvic nerves) to the organs where they act. Within the abdominal region, the vagus nerve supplies the following organs: stomach, liver, gall bladder, pancreas, kidneys, small intestine and parts of the large intestine.
Apart from the kidneys, these are digestive organs. A parasympathetic effect mainly promotes intestinal movements and the secretion of the organs. Digestive secretions are formed and released which, in interaction with the intestinal movement, enable the comminution, movement and digestion of food.
The nervus vagus or parasympathetic nerve has a damping effect on the heart. However, it only acts on the atrium of the heart, which is responsible for the frequency and can therefore only slow down the heartbeat (pulse) and not directly lower the beating power (blood pressure). However, this effect still occurs because the parasympathetic and sympathetic nervous systems influence and inhibit each other as antagonists. The parasympathetic nervous system thus inhibits the strengthening function of the sympathetic nervous system of the heart.
