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{{BioPsy}}
 
{{BioPsy}}
The '''Retinohypothalamic tract''' (RHT) is a photic input pathway involved in [[circadian rhythms]]. The RHT is the input pathway to the [[suprachiasmatic nucleus]], and is important in the [[entrainment]] of our 'body clock' to the external environment. The retinal cells involved in the RHT are photoreceptive retinal [[ganglion cells]], which contain [[melanopsin]]. The information these retinal cells receive on day-length is interpreted by the SCN, and passed onto the [[pineal gland]], which then secretes the hormone [[melatonin]] in response to this [[exogenous]] environmental signal.
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The '''retinohypothalamic tract''' is a photic input pathway involved in the [[circadian rhythms]] of [[mammal]]s.<ref name="pmid11713469">{{cite journal |author=Gooley JJ, Lu J, Chou TC, Scammell TE, Saper CB |title=Melanopsin in cells of origin of the retinohypothalamic tract |journal=[[Nat. Neurosci.]] |volume=4 |issue=12 |pages=1165 |year=2001 |pmid=11713469 |doi=10.1038/nn768}}</ref> The origin of the retinohypothalamic tract is the [[photosensitive ganglion cell|intrinsically photosensitive retinal ganglion cells]] (ipRGC), which contain the photopigment [[melanopsin]]. The axons of the ipRGCs belonging to the retinohypothalamic tract project directly, monosynaptically, to the [[suprachiasmatic nuclei]] via the [[optic nerve]] and the [[optic chiasm]].<ref>from the retina to the optic chiasm, the ipRGC axons follow the same path as the axons of "regular" [[retinal ganglion cell|RGCs]] (i.e. RGCs that are not intrinsically photosensitive)</ref><ref>{{cite book |last=Afifi |first=A.K. |last2=Bergman |first2=R.A. |title= Functional Neuroanatomy |url=http://www.mhprofessional.com/product.php?cat=116&isbn=0071408126&cat=116 |format=paperback |edition=2nd |date=2005-01-28 |publisher=McGraw-Hill |isbn=978-0-07-140812-7 |page=271 |doi= 10.1036/0071408126}}</ref> The suprachiasmatic nuclei receive and interpret information on environmental light, dark and day length, important in the [[entrainment (chronobiology)|entrainment]] of the "body clock". They can coordinate peripheral "clocks" and direct the [[pineal gland]] to secrete the hormone [[melatonin]].
   
[[Category:Circadian rhythms]]
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==References==
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{{reflist}}
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[[Category:Eye]]
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[[Category:Sleep physiology]]
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[[Category:Circadian rhythm]]
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{{enWP|Retinohypothalamic tract}}

Latest revision as of 23:08, October 2, 2013

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The retinohypothalamic tract is a photic input pathway involved in the circadian rhythms of mammals.[1] The origin of the retinohypothalamic tract is the intrinsically photosensitive retinal ganglion cells (ipRGC), which contain the photopigment melanopsin. The axons of the ipRGCs belonging to the retinohypothalamic tract project directly, monosynaptically, to the suprachiasmatic nuclei via the optic nerve and the optic chiasm.[2][3] The suprachiasmatic nuclei receive and interpret information on environmental light, dark and day length, important in the entrainment of the "body clock". They can coordinate peripheral "clocks" and direct the pineal gland to secrete the hormone melatonin.

ReferencesEdit

  1. Gooley JJ, Lu J, Chou TC, Scammell TE, Saper CB (2001). Melanopsin in cells of origin of the retinohypothalamic tract. Nat. Neurosci. 4 (12): 1165.
  2. from the retina to the optic chiasm, the ipRGC axons follow the same path as the axons of "regular" RGCs (i.e. RGCs that are not intrinsically photosensitive)
  3. Afifi, A.K. (2005-01-28). Functional Neuroanatomy (paperback), 2nd, McGraw-Hill.
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