Forskel mellem versioner af "Bruger:Christian89/projekter"

De er opkaldt efter deres [[Tjekkiet|tjekkiske]] opdager [[Jan Evangelista Purkyně]].
[[Image:Gray706.png|thumb|200px|left|Transverse section of a cerebellar [[folium (brain)|folium]]. (Purkinje Cell labeled at center top.)]]
[[Image:Cerebellum - biel - very high mag.jpg|thumb|left|Purkinje cells. [[Bielschowsky stain]].]]
Purkinje celler er nogle af de største celler i menneskehjenen (med [[Betz celle]]r som de største)<ref name="Purves" >{{cite book | author = Purves, Dale, George J. Augustine, David Fitzpatrick, William C. Hall, Anthony-Samuel LaMantia, James O. McNamara, and Leonard E. White | title = Neuroscience. 4th ed. | publisher = Sinauer Associates | pages = 432–4 | year = 2008 | isbn = 978-0-87893-697-7}}</ref> indviklet detaljeret dendrittræ som er karakteriseret ved det store antal af dendritiske fremskud (en: Spines). Purkinje cellerne forekommer i lillehjernens såkaldte Purkinje lag.
Purkinje cells are aligned like [[domino]]s stacked one in front of the other. Their large dendritic arbors form nearly [[two-dimensional]] layers through which [[parallel fiber]]s from the deeper-layers pass. These parallel fibers make relatively weaker [[excitatory synapse|excitatory]] ([[glutamatergic]]) synapses to spines in the Purkinje cell dendrite, whereas [[climbing fibers]] originating from the [[inferior olivary nucleus]] in the [[medulla oblongata|medulla]] provide very powerful excitatory input to the proximal dendrites and cell soma. Parallel fibers pass [[orthogonal]]ly through the Purkinje neuron's dendritic arbor, with up to 200,000 parallel fibers<ref>{{cite journal|last=Tyrrell|first=T|coauthors=Willshaw, D|title=Cerebellar cortex: its simulation and the relevance of Marr's theory.|journal=Philosophical transactions of the Royal Society of London. Series B, Biological sciences|date=1992-05-29|volume=336|issue=1277|pages=239–57|pmid=1353267|doi=10.1098/rstb.1992.0059}}</ref> forming a [[Granule-cell-Purkinje-cell synapse]] with a single Purkinje cell. Each Purkinje cell receives ca 500 climbing fiber synapses, all originating from a single climbing fiber.<ref>{{cite journal|last=Wadiche|first=JI|coauthors=Jahr, CE|title=Multivesicular release at climbing fiber-Purkinje cell synapses|journal=Neuron|date=2001-10-25|volume=32|issue=2|pages=301–13|pmid=11683999|doi=10.1016/S0896-6273(01)00488-3}}</ref> Both basket and stellate cells (found in the cerebellar [[Cerebellum#Molecular Layer|molecular layer]]) provide [[inhibitory]] (GABAergic) input to the Purkinje cell, with basket cells synapsing on the Purkinje cell axon initial segment and stellate cells onto the dendrites.
Purkinje cells send inhibitory projections to the deep cerebellar nuclei, and constitute the sole output of all [[motor coordination]] in the cerebellar cortex.
== Elektrofysiologi ==
[[Image:CerebCircuit.png|thumb|right|200px|Microcircuitry of the cerebellum. [[Excitatory synapses]] are denoted by (+) and [[inhibitory synapses]] by (-).<BR>MF: [[Mossy fiber (cerebellum)|Mossy fiber]].<BR>DCN: [[Deep cerebellar nuclei]].<BR>IO: [[Inferior olivary nucleus|Inferior olive]].<BR>CF: [[Climbing fiber]].<BR>GC: [[Granule cell]].<BR>PF: [[Parallel fiber]].<BR>PC: Purkinje cell.<BR>GgC: [[Golgi cell]].<BR>SC: [[Stellate cell]].<BR>BC: [[Basket cell]].]]