Nucleus tractus solitarius




The solitary nucleus is a series of purely sensory nuclei in the brain stem that form a vertical column of grey matter embedded in the medulla oblongata. 



The nucleus of the solitary tract, also known as the nucleus tractus solitarius is a pair of cell bodies found in the brainstem. 



This structure, along with its tract the solitary tract or tractus solitarius,has far reaching impacts on many homeostatic systems within the body.



Through the center of the SN runs the solitary tract, a white bundle of nerve fibers, including fibers from the facial, glossopharyngeal and vagus nerves, that innervate the SN. 



The nucleus tractus solitariius projects to, among other brain regions: the reticular formation, parasympathetic preganglionic neurons, hypothalamus and thalamus.



Its circuitry contributes to autonomic regulation. 



Cells along its length are arranged roughly in accordance with function.



Cells involved in taste are located In the rostrum part, while those receiving information from cardio-respiratory and gastrointestinal processes are found in the caudal part.



Taste information comes from the facial nerve via the chorda tympani in the anterior 2/3 of the tongue, the posterior glossopharyngeal nerve and the vagus nerve on the epiglottis.



It receives chemoreceptors and mechanoreceptors of the general visceral afferent pathway in the carotid body via glossopharyngeal nerve, aortic bodies, and the sinoatrial node, via the vagus nerve.



Chemical and mechanical sensitive neurons of the general visceral afferent pathway with endings located in the heart, lungs, airways, gastrointestinal system, pharynx, and liver via the glossopharyngeal and vagus nerves are present.



Additional minor visceral input comes from the nasal cavity, soft palate and sinus cavities entering via the facial nerve.



The nucleus tract solitarius is innervated with nerves that mediate the gag reflex, the carotid sinus reflex, the aortic reflex, the cough reflex, the baroreceptor and chemoreceptor reflexes, several respiratory reflexes and reflexes within the gastrointestinal system regulating motility and secretion.



Neurons transmit signals to the nucleus tract solitarius from  the gut wall, the stretch of the lungs, and the dryness of mucous membranes.



Central neurons within the solitary nucleus can participate in autonomic reflexes.



The solitary nucleus provides information to a large number of other regions of the brain:  paraventricular nucleus of the hypothalamus and the central nucleus of the amygdala, nuclei in the brainstem, and visceral motor or respiratory networks.




The pathways for gastric and gustatory processes are believed to terminate in different subdivisions of the parabrachial  nuclei area, but still interact in the solitary nucleus.



Lies in the brainstem and is the target for central acting antiemetics.

Neurokinin 1 receptors (NK1) in the NTS are inhibited by NK1 antagonists to control chemotherapy induced emesis.

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