Solitary nucleus 684085 212930249 2008-05-16T22:32:47Z Arcadian 104523 nav {{Merge|Solitary tract|date=May 2007}} {{Infobox Brain| Name = {{PAGENAME}} | Latin = tractus solitarius medullae oblongatae | GraySubject = | GrayPage = | Image = Gray696.png | Caption = The [[cranial nerve nuclei]] schematically represented; dorsal view. Motor nuclei in red; sensory in blue. | Image2 = Gray648.png | Caption2 = Transverse section of [[medulla oblongata]] of human [[embryo]]. | IsPartOf = | Components = | Artery = | Vein = | BrainInfoType = hier | BrainInfoNumber = 739 | MeshName = Solitary+Nucleus | MeshNumber = A08.186.211.132.810.406.750 | DorlandsPre = t_15 | DorlandsSuf = 12817166 | }} The '''solitary nucleus''' and '''tract''' are structures in the [[brainstem]] that carry and receive visceral sensation and [[taste]] from the [[facial nerve|facial]] (VII), [[glossopharyngeal nerve|glossopharyngeal]] (IX), [[vagus nerve|vagus]] (X) [[cranial nerves]], as well as the cranial part of the [[accessory nerve]] (XI). ==Anatomy== The nucleus is located along the length of the medulla (with a small portion in the lower [[pons]]). The solitary tract runs in the middle of the nucleus, creating a speck of [[white matter]] (axons of the tract), surrounded by [[grey matter]] (the nucleus). This stands out on a stained section, which is where the name solitary comes from. The solitary nucleus is divided into a rostral (towards the top) [[gustatory nucleus]] and caudal (towards the bottom) region of neurons. Sub regions of the solitary nucleus can be related to the distribution of inputs - particularly contacts from cranial primary afferent neurons (see below) related to cardiovascular, respiratory and gastrointestinal functions. There is some degree of localization within the caudal region so that many cardiovascular neurons sit near the midline of the nucleus, and many respiratory related neurons are located laterally within the nucleus. ==Inputs to the solitary nucleus== In addition to afferent taste information from nerves VII, IX and X, the solitary nucleus also handles primary afferent signals from a variety of visceral regions and organs. These afferents include chemoreceptors in the [[carotid body|carotid]] (via IX) and [[Aortic body|aortic bodies]] (via X) as well as stretch receptors from the aorta and carotid arteries called arterial baroreceptors. In addition, chemically and mechanically sensitive neurons with endings located in the heart, lungs, airways, gastrointestinal system, liver and other viscera send axons via cranial nerves (IX and X) chiefly that directly enter the brainstem to form synapses within the caudal third of the solitary nucleus. Neurons that synapse in this nucleus 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. Information about the gut wall, as well as stretch of the [[lungs]] and dryness of [[mucous membrane]]s, also [[synapse]]s at the solitary nucleus. These first central neurons within the solitary nucleus can participate in autonomic reflexes that may be as simple as two central neurons with the second neuron being an efferent or motor neuron that projects back directly to the organ such as the heart forming some of the simplest reflex pathways in the brain. ==Outputs from the solitary nucleus== Information goes from the solitary nucleus to a large number of other regions of the brain including the [[hypothalamus]] and [[cingulate gyrus]], as well as to other nuclei in the brainstem (such as visceral motor or respiratory networks). ==Additional images== <gallery> Image:Gray694.png|Section of the medulla oblongata at about the middle of the olive. Image:Gray698.png|Primary terminal nuclei of the afferent (sensory) cranial nerves schematically represented; lateral view. </gallery> ==External links== * [http://cal.vet.upenn.edu/neuro/server/slides/ns_024-NS.jpg Slide at University of Pennsylvania] * {{BrainMaps|solitary%20tract|solitary tract}} {{Rhombencephalon}} {{Cranial nerves}} {{Gustatory system}} [[Category:Nervous system]]