30 OPTM4102_Visual pathway I.pdf

OPTM4102 Visual pathway I Retina Dr. Jason Charng [email protected] Acknowledgement of country The University of Western Australia acknowledges that its campus is situated on Noongar land, and that Noongar people remain the spiritual and c...

OPTM4102 Visual pathway I Retina Dr. Jason Charng [email protected] Acknowledgement of country The University of Western Australia acknowledges that its campus is situated on Noongar land, and that Noongar people remain the spiritual and cultural custodians of their land, and continue to practise their values, languages, beliefs and knowledge. Artist: Dr Richard Barry Walley OAM Objectives Visual signal transmission photoreceptors to ganglion cells  make up the 3 pathways. make up the lateral pathway Mammalian retina light energy has been once converted to electrical these signals energy within the photoreceptor , passes to the bipolar cells and then ganglion cells. While horizontal cells and amacrine cells modify these signals along the way. Photoreceptors Horizontal cells Bipolar cells Amacrine cells Ganglion cells https://www.nature.com/articles/nn0901-877  end of photoreceptors. terminal (the At the acron Photoreceptor/Bipolar cell synapse The junction between rods or comes with bipolar cell & nibereits Ribbon synapse crycled blue) => specialized organelle find In retinal , in in the ascon terminal Outer plexiform layer (photoreceptor to bipolar cell) e Inner plexiform layer (bipolar cell to ganglion cell) rates of neurotransmitter release. Find in synapse with singling requires high The main neurotransmitter for signal properation in the retina is glutamate. accon terminal have multiple can Des ribbon Syna https://pubmed.ncbi.nlm.nih.gov/15626493/  Photoreceptor/Bipolar cell synapse ribbon at cone pedicle synapse is more complex than spherule Dipolar cells.. have ON only Come pedicle have multiple ribbon synapse. spherule Horizontal one rod only have one. Can Contact cone OFF & Cone ON S ⑥ Cone pedicle cell OFF BP terminal rod ON BP - - - Spherule : ascon in -. - https://webvision.med.utah.edu/book/part-iii-retinal-circuits/circuitry-for-rod-cells-through-the-retina/ https://pubmed.ncbi.nlm.nih.gov/10939333/ ON bipolar cell Rod - ON bipolar cell ON Cone - - bipolar cell OFF bipolar cell Metabotropic glutamate receptor 6 (mGluR6) is the primary receptor type at ON bipolar cells (rod bipolar, cone ON bipolar) -- In the presence of glutamate (i.e. dark), ON BP cell inactive (i.e. hyperpolarise) In the absence of glutamate (i.e. light), ON BP cell active (i.e. depolarise) depolarization of the ON bipolar cell due to the movement of cations induce hyperpolarization into the cell O cell. of the ON bipolar thehe Glutamate binds to= cationscannotenter :: to the receptor leads space - TRPM1 , inhibition of channel. https://physoc.onlinelibrary.wiley.com/doi/full/10.1113/JP270006  Cone OFF bipolar cell AMPA is # selective for transient signals. F Kainate is selective for sustained signals. : Ionotropic glutamate receptor exhibit - types dominate cone OFF bipolar cell creceptors ( dendrites the opening allows channels - Two subtypes expressed (AMPA, O - of cation kainate) – temporal characteristics - - - In the presence of glutamate (i.e. dark), cone OFF BP cells active (i.e. depolarise) In the absence of glutamate (i.e. light), coneOFF BP cells inactive (i.e. hyperpolarise) (Dark glutamate v => active - Come OFF BD Cell glutamate x => Inactive. (Light) http://pittmedneuro.com/glutamate.html  Bipolar cell subtypes Roc sublamina 3-5 Bipolar ON bipolar cell tend to stratify Cell OFF Dipolar cell Hone well stratify bipolar. tend to 51-2. have multiple dendrites to => connect to multiple photoreceptor & only type contact one cone. https://webvision.med.utah.edu/book/part-ii-anatomy-and-physiology-of-the-retina/oute-plexiform/  Ganglion cells photoreceptors. to the closer ON and OFF ganglion cells q Sublamina 1 , 2 E ~ OFF bipolar cells and OFF ganglion cells synapse @ IPL sublamina a - ~ ON bipolar cells and ON ganglion cells synapse @ IPL sublamina b => Sublamina 3-5 Rod BP do not contact ganglion cell Rod BP Amacrine https://www.ncbi.nlm.nih.gov/books/NBK11521/ https://pubmed.ncbi.nlm.nih.gov/11528418/  Ganglion cells - subtypes 5 e Parasol Midget Bistratified Photosensitive response light =>input without from photoreceptors. Projecting to superior colliculus ↳ movements. role in controlling eye https://www.ncbi.nlm.nih.gov/books/NBK11521/  Ganglion cells - subtypes ON OFF not both) account Parasol and midget are uni-strictified. (either connect to or ,. most of for out the T - Parasol I ~ Larger receptive field than midget ganglion cells ~ Input to magnocellular layers in the LGN ~ Detect low contrast, movement sensitive Midget ~ Smaller receptive field ~ Input to parvocellular layers in the LGN ~ Perception of colour and fine detail Bistratified ~ S cone pathway ~ Proprioception? a IPL b Oyster (1999) main role : provide feedback to the photoreceptors & Horizontal cells – lateral pathway Interneuron HI: Connect to all cone types all have Dendrites in outer plexiform accons : HII: Connect primarily to S cones and rods layer (i.e. ribbon synapse), cell HIII: Connect L and M cones body in inner nuclear layer