The vertebrate ear o semi circular canals involved

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Midterm 2 ReviewoPhotoreceptors: transduce energy from photons into changes in membrane potential oPhotoreceptive organs: structures specialized for light detection, encode direction of light and contrasts Evolutionary significance of the visible spectrum of lightoEvolved from water because there is a gap of wavelength that passes through water and that is what our photoreceptors can seeRhabdomeric and ciliary photoreceptor classesoRhabdomericclasses: apical surface contains photopigments in microvillar projections (compound eye)oCiliaryclasses: rods and cones (single cilium projection)Photoreceptor cell vs. photopigmentoPhotopigment: protein with chromophore that changes conformationwhen it absorbs light Evolution and anatomy of the eyeoCamera eye, compound eye, flat sheet eye, eye cupExamplesVisible spectrum: humans 350-750nmPhotoreceptor diversity: vertebrates have two types of ciliary photoreceptors(rods and cones)oNocturnal animals have higher ratio of rods to cones oFrog’s rods detect colouroTurtle’s cones detect colourReceptor protein: retinalPhotopigments: rhodopsin, iodopsin, melanopsinChromophore activation: 11-cis retinal to all-trans retinal Image formation without eye: Sea urchinsoDiffuse dermal photoreceptors and spines provide directional sensitivityoOrient themselves using spines to figure out where light is coming from Accommodation of lens: polychaetes change volume of fluid in eye to change distance between lens and retinaCompound eye: Dragonflies have added more receptors in order to get better resolution because they’re aerial huntersApposition eye: Diurnal insectsSuperposition eye: nocturnal insects Cephalopod eye: photoreceptors located on surface of retina, support cells between photoreceptors and axons of photoreceptors from optic nerve PathwaysPhototransduction in Rhabdomeric photoreceptors o11-cis-3-hydroxy retinal absorbs light and isomerizes into all-trans-3-hydroxy retinal
Midterm 2 ReviewoAll-trans-3-hydroxy retinal dissociates from opsinoActivated opsin activates a Gq proteinoActivated Gq protein activates PLC, converting PIP2 to DAG and IP3oDAG activates a TRP cation channeloCalcium and sodium enter the cell- depolarizing itPhototransduction in vertebrate photoreceptors o11-cis retinal absorbs light and isomerizes into all-trans retinaloAll-trans retinal dissociates from opsinoActivated opsin activates the Gi protein transducinoTransducin activates PDE which converts cGMP to GMPoThe decrease cGMP closes a sodium channeloSodium entry decreases hyperpolarizing the cellVertebrate: when light hits photoreceptors, hyperpolarizes and stops the message saying there is not lightLight responses: Activated opsintransducinActive posphodiesterasedecrease in cGMPsodium channels closehyperpolarization

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