WordNet

an automatic instinctive unlearned reaction to a stimulus (同)reflex response, reflex action, instinctive reflex, innate reflex, inborn reflex, unconditioned_reflex, physiological reaction
of or relating to the throat; "pharyngeal fricatives"
(of leaves) bent downward and outward more than 90 degrees

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反射(刺激に対する無意識の反応) / 《複数形で》反射的な動き / (光などの)反射,反射光;映像 / 反射性の / (カメラが)レフ鋼の,反射型の

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/06/18 12:39:40」(JST)

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The pharyngeal reflex or gag reflex is a reflex contraction of the back of the throat,^[1] evoked by touching the soft palate and occasionally the back of the tongue. It prevents something from entering the throat except as part of normal swallowing and helps prevent choking.

Reflex arc

In a reflex arc, a series of physiological steps occur very rapidly to produce a reflex. Generally a sensory receptor receives an environmental stimuli, in this case from objects reaching nerves in the back of your throat, and sends a message via an afferent nerve to the central nervous system (CNS). The CNS receives this message and sends an appropriate response via an efferent nerve (also known as a motor neuron) to effector cells located in the same initial area that can then carry out the appropriate response.^[2]

The afferent limb of this reflex is supplied by the glossopharyngeal nerve (cranial nerve IX), which synapses on the nucleus solitarius and the spinal trigeminal nucleus, both nuclei in the medulla oblongata in the brain stem. The efferent limb is supplied by the vagus nerve (cranial nerve X) from the nucleus ambiguus, also located in the medulla in the brain stem.

Suppression and activation

Swallowing unusually large objects or placing objects in the back of the mouth may cause the pharyngeal reflex. Some people, for instance sword swallowers, have learned how to suppress it.^[2] In contrast, triggering the reflex is sometimes done intentionally to induce vomiting, for example by those who suffer from bulimia nervosa.

Its absence

Absence of the gag reflex and pharyngeal sensation can be a symptom of a number of severe medical conditions, such as damage to the glossopharyngeal nerve, the vagus nerve, or brain death. However, in one study, one-third of healthy people did not have a gag reflex, although pharyngeal sensation in these subjects remained intact.^[3]

References

^ "Medical Neurosciences". http://www.neuroanatomy.wisc.edu/virtualbrain/BrainStem/09NA.html.
^ ^a ^b Wilson, Tracy V.. "How Sword Swallowing Works" 29 June 2007. HowStuffWorks.com. <http://entertainment.howstuffworks.com/arts/circus-arts/sword-swallowing.htm>
^ Pharyngeal sensation and gag reflex in healthy subjects. Davies, A., Kidd, D., Stone, S., MacMahon, J. (1995). Lancet 345:487–488

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UpToDate Contents

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English Journal

NHS can use gagging clauses as long as employees know they don't apply to safety issues, guidance says.

Dyer C.SourceBMJ.
BMJ (Clinical research ed.).BMJ.2013 Apr 23;346:f2606. doi: 10.1136/bmj.f2606.
PMID 23613542

The Distribution of TRPV1 and TRPV2 in the Rat Pharynx.

Sasaki R, Sato T, Yajima T, Kano M, Suzuki T, Ichikawa H.SourceDivision of Oral and Craniofacial Anatomy, Graduate School of Dentistry, Tohoku University, 4-1 Seiryo-machi, Sendai, 980-8575, Japan.
Cellular and molecular neurobiology.Cell Mol Neurobiol.2013 Apr 14. [Epub ahead of print]
Immunohistochemistry for two nociceptive transducers, the transient receptor potential cation channel subfamily V members 1 (TRPV1) and 2 (TRPV2), was performed on the pharynx and its adjacent regions. TRPV1-immunoreactivity (IR) was detected in nerve fibers beneath and within the epithelium and/or
PMID 23584686

Japanese Journal

Autonomic Responses Associated with Severe Gagging Elicited by Stimulation of the Superior Laryngeal Nerve in Rats

Yamagata Ryuzo,Koga Tomoshige
Kawasaki journal of medical welfare 18(1), 1-11, 2012-00-00
… While severe gagging is associated with problems in oral feeding in children, routine dental treatment and gastrointestinal endoscopy, little is known about the neural mechanism of this reflex. … In the present study using decerebrate rats, we observed dynamic changes in the activities of the costal and crural diaphragm, abdominal muscles, and infrahyoid muscles, and in pharyngeal and esophageal pressure during severe gagging, and determined the most suitable stimulation of the superior laryngeal nerve (SLN) for induction. …
NAID 110009477414

失神発作を初発症状とした上咽頭癌の1症例

卯月彩,嶋根俊和,秋山理央,林武史,池田賢一郎,五味渕寛,小林斉,三邉武幸
頭頸部外科 21(3), 241-245, 2012
頭頸部癌は頸部リンパ節転移が多く認められ，この転移巣による物理的な頸動脈圧迫で失神発作（頸動脈洞過敏症候群：Carotid Sinus Hypersensitivity Syndrome以下CSHS）を起こすことは報告されているが，ほとんどは末期癌患者であり初発症状として失神発作を起こした症例は少ない。今回，われわれは頻回の失神発作を初発症状とした，上咽頭癌の頸部リンパ節転移の症例を経験した。術前 …
NAID 130002137068

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