wiki笔记--Solitary nucleus--2021/7/21
Solitary nucleus
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Solitary nucleus
The cranial nerve nuclei schematically represented; dorsal view. Motor nuclei in red; sensory in blue.
Transverse section of medulla oblongata of human embryo.
Details
Identifiers
Latin
Nucleus tractus solitarii medullae oblongatae.
MeSH
D017552
NeuroNames
742
NeuroLex ID
birnlex_1429
TA98
A14.1.04.230
TA2
6008
FMA
72242
Anatomical terms of neuroanatomy
[edit on Wikidata]
In the human brainstem, the solitary nucleus (SN) (nucleus of the solitary tract, nucleus solitarius, nucleus tractus solitarii) is a series of purely sensory nuclei(clusters of nerve cell bodies) forming a vertical column of grey matter embedded in the medulla oblongata. 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 SN projects to, among other regions, the reticular formation, parasympathetic preganglionic neurons, hypothalamus and thalamus, forming circuits that contribute to autonomic regulation. Cells along the length of the SN are arranged roughly in accordance with function; for instance, cells involved in taste are located in the rostral part, while those receiving information from cardio-respiratory and gastrointestinal processes are found in the caudal part.[1][2]
Contents
· 1Inputs
· 2Outputs
· 3Additional images
· 4See also
· 5References
· 6External links
Inputs[edit]
· Taste information from the facial nerve via the chorda tympani (anterior 2/3 of the tongue), glossopharyngeal nerve (posterior 1/3) and vagus nerve (small area on the epiglottis)
· Chemoreceptors and mechanoreceptors of the general visceral afferent pathway (GVA) in the carotid body via glossopharyngeal nerve, aortic bodies, and the sinoatrial node, via the vagus nerve
· Chemically and mechanically sensitive neurons of the general visceral afferent pathway (GVA) with endings located in the heart, lungs, airways, gastrointestinal system, pharynx, and liver via the glossopharyngeal and vagus nerves. Additional minor GVA input from the nasal cavity, soft palate and sinus cavities enters via the facial nerve.[3]
Neurons that innervate the SN 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.
(可能指的是打喷嚏这样的本能反应由solitary nucleus来触发。)
Neurons which transmit signals about the gut wall, the stretch of the lungs, and the dryness of mucous membranesalso innervate the SN.
（dry mucous membrane hurt easily, then this pain information is sent in to excite parasympathetic system in order to secrete more mucus.）
The first central neurons within the SN can participate in simple autonomic reflexes.
Outputs[edit]
Information goes from the solitary nucleus to a large number of other regions of the brain including the paraventricular nucleus of the hypothalamus and the central nucleus of the amygdala
(对于central nucleus，这应该是在打喷嚏这样的本能反应时激发吧),
as well as to other nuclei in the brainstem (such as the parabrachial area, the locus coeruleus, the dorsal raphe nucleus, and other visceral motor or respiratory networks).[4] The signals projected from the SN to the parabrachial area originate in the oral cavity and gastrointestinal tract. The pathways for gastric and gustatory (taste) processes are believed to terminate in different subdivisions of the parabrachial area, but still interact in the SN.[5][6] Some neuronal subpopulations in the SN, such as the noradrenergic cell group A2 and the aldosterone-sensitive HSD2 neurons project as far ventral as the bed nucleus of the stria terminalis.[7][8]
（自主神经系统的各个器官由smooth muscle和gland组成，并且其活动由位于脊髓以外的自主神经节控制，虽然自主神经系统高度自治，仍然会将系统中收集的sensory information上传到中枢系统--即solitary nucleus，并且接受中枢系统中相应核团的控制--即preganglionic nuclei。所谓的sensory information主要来自于平滑肌的被动扩张，可以回忆一下憋尿的膀胱带来的感受，食物落入食道中使管壁的平滑肌扩张，这些感受都能很明显地影响人的感受，但是食物在小肠内的活动应该是小肠主动运动的结果，而不同于胃被动地接收食物，所以说我们能够明显感觉到胃以及十二指肠的存在（胃酸能与十二指肠中的碱性液体中和产生二氧化碳），但是很难感觉到小肠的存在，可但是，吃了太多油腻食物而导致食物快速从小肠滑过，你就会感觉到自己有些异样，有些晕，然后就是粑粑比平时来的更早一些、更顺畅一些，原因在于：solitary nucleus的一个输出到达locus coeruleus和dorsal raphe nucleus，于是大量来自小肠的sensory information兴奋solitary nucleus进而兴奋locus coeruleus的抑制型细胞而抑制locus coeruleus从而使大脑皮层、丘脑兴奋度降低，兴奋dorsal raphe nucleus从而进一步使得大脑皮层的兴奋度降低，人就感觉外界事物有些奇怪，自己有些晕的乎。
其实，对于去甲肾上腺素在大脑中的分泌浓度，教科书中指出在饱食之后浓度极低，但是没有给出浓度低的原因。其实当我了解到solitary nucleus输出到locus coeruleus时，我立马就意识到solitary nucleus的这个轴突输出应该是兴奋型递质，但是却起到抑制locus coeruleus的作用，从而强烈抑制住了NE放大环路，这仅仅是在胃内食物流向小肠时才强烈激发solitary nucleus，并不影响DA system来控制行为，只要脑岛做好抑制central nucleus的工作。饱食状态下，如果还出现central nucleus明显活动，这样就意味着central nucleus抑制抑制型神经元，从而让locus coeruleus活动，允许交感系统活动，让NE放大环路随时被激发，从而兴奋