Nucleus tractus solitarii

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Diagram of the brain stem from the dorsal side with the diamond pit as the floor of the fourth cerebral ventricle in the center of the picture, below on the right in the picture the nucleus tractus solitarii (shown in blue).

The nucleus tractus solitarii , also Nuclei tractus solitarii , or nucleus solitarius is an extensive region of gray matter of the medullary brain that lies dorsally in its hood .

The complex contains a number of (sub) nuclei as nuclei , onto which the primary visceroafferent fibers of the three cranial nerves the facial nerve (VII), glossopharyngeal nerve (IX) and vagus nerve (X) project, in the upper section also special of the sense of taste . These “nuclei of the solitary tract” - grouped around the solitary tract , a web of white matter - form a vertical column of gray matter in the lower brain stem .

Location and structure

Over the entire length of the elongated medulla ( medulla oblongata ) or medullary brain ( myelencephalon ) extends within the medullary dome ( tegmentum myelencephali ) - from the transition into the spinal cord at the level of the pyramid junction caudally (below) to the vicinity of the area postrema and rostral (above) reaching to the viscerosensory zone of the caudal pons - on each side the nucleus tractus solitarii called the viscerosensory core area, which the tractus solitarius runs through.

In humans, about a dozen (sub) nuclei are neuroanatomically differentiated in this region :

  • Nuclei tractus solitarii
    • Nucleus parasolitarius
    • Nucleus commissuralis
    • Nucleus gelatinosus solitarius
    • Nucleus intermedius solitarius
    • Solitary interstitial nucleus
    • Nucleus medialis solitarius
    • Nucleus paracommissuralis solitarius
    • Nucleus solitarius posterior
    • Solitarius posterolateral nucleus
    • Nucleus solitarius anterior
    • Nucleus solitarius anterolateralis

The neurons of the core areas of the complex work with quite different neurotransmitters , and already under this aspect make it a diverse brain region. In addition to cholinergic neurons, there are numerous peptidergic neurons with transmitters such as vasoactive intestinal peptide , corticoliberin or dynorphin .

The core complex can be roughly divided into three sections: a caudal, a medial and a rostral, which is also known as the pars gustatoria or nucleus gustatorius . The nucleus ovalis is considered to be its rostral extension .

In the pars gustatoria of the nucleus tractus solitarii , specially viscerosensitive fibers of pseudounipolar ganglion cells from the ganglion geniculi of the facial nerve , from the ganglion inferius (petrosum) of the nervus glossopharyngeus and from the ganglion inferius (nodosum) of the nervus vagus end . The geniculate ganglion leads to afferents from taste papillae from the anterior two-thirds of the tongue, the petrosal ganglion from the posterior third of the tongue and the nodose ganglion to afferents from taste buds from the epiglottis and the base of the tongue to the gustatory nucleus. Viscera afferents of the facial nerve also reach the rostrally adjacent nucleus ovalis.

In the medial and caudal core areas, which are also known as the pars cardiorespiratoria , the generally visceroafferent fibers of the glossopharyngeal and vagus nerves end. They innervate u. a. the mucous membranes of the throat and larynx and carry fibers from the chemoreceptors in the carotid body and baroreceptors (Drucksinneskörperchen) in the carotid sinus .

The tractus solitarius mainly leads descending primary afferent fibers to the equilateral core areas, and also slightly ascending to those that cross in the caudal section. The as solitary nucleus designated core complex is located immediately to the solitary tract around.

function

As the name Nucleus gustatorius ("taste core") suggests, taste fibers come to this core area . However, a conscious gustatory sensory impression can only arise if the signals are passed on from here ( efferent ) after processing in these nuclei of the medullary brain , and after switching in the thalamus of the diencephalon - to small-cell neurons of the nucleus ventralis posteromedialis (VPM) - finally also areas of the cerebral cortex ( Cortex cerebri ) in the endbrain , so in the operculum parietale and in the insula .

At the level of the lower brain stem, however, the signals from the specially viscerosensitive taste buds play a different role and are important in (vital) interconnections for functions of food intake and digestion . This way, impulses can emanate from here that increase the flow of saliva , stimulate chewing movements and also trigger the act of swallowing (as well as stimulating the release of digestive juices). On the other hand, swallowing can be made difficult and intake refused. Furthermore, choking, coughing or sneezing can be conveyed - as a defense reaction or as a protective reflex to keep the airways free.

In addition to the special viscerosensory primary afferents of the sense of taste, the nuclei tractus solitarii reach other primary afferents, in addition to some somatosensory predominantly general viscerosensory ones. Afferents from other brain regions include, for example, those from the dorsally adjacent area postrema in the wall of the fourth ventricle ; conversely, efferents from the solitary nucleus reach this region. These can cause vomiting , although the processed emetogenic stimulus does not necessarily have to be a taste stimulus. B. also the gastrointestinal tract are irritated.

literature

Web links

Individual evidence

  1. ↑ Gustatory system and sense of taste. (PDF; 1.2 MB) in Anatomie.net , accessed on August 13, 2008
  2. ↑ see Terminologia Anatomica (TA), p. 111 (A.14.1.04.230 to A.14.1.0.04.241).
  3. ^ D. Drenckhahn: Benninghoff Taschenbuch Anatomie , Urban and Fischer bei Elsevier, 2007, p. 425ff.
  4. ↑ K. Possinger et al. a .: Antiemetic treatment in cytostatic chemotherapy. In: Dtsch Arztebl 98/2001, A-924 / B-776 / C-723