2020 Bio 3303 06 Sensory Biology 2 Notes-2.pptx -...

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AnnouncementsWelcome back!Assignment #3 is due March 6thMid-term #2 is on March 9thAll of sensory physiologyBIO3303
Mechanoreceptor ion channels are attached to extracellular matrix proteins and to the cytoskeletonThere are many types of mechanoreceptors and two types of mechanorecpetor proteinsTouch and pressureBaroreceptors, tactile receptors and proprioceptorsEquilibrium and hearingInvertebrates have statocyctsVertebrates have hair cellsSome aquatic animals have electroreceptionThe vertebrate earSemi-circular canals involved with equilibriumCochlea senses involved with hearingPrevious HighlightsBIO 3303
Name two animals that have specializations for hearing and briefly explain what they are.Knowledge Test
Sensory Physiology (4 of 6)By the end of this lecture, you should understand…Photoreceptors vs. photoreceptive organsEvolutionary significance of the visible spectrum of lightRhabdomeric and ciliary photoreceptor classesPhotoreceptor cell vs photopigmentEvolution and anatomy of the eyeReceptive fields and lateral inhibitionBIO3303
PhotoreceptionBIO 3303Fig. 6.40/7.42
PhotoreceptionPhotoreceptorstransduce energy from photons into changes in membrane potentialPhotopigment(protein with chromophore) changes conformation when absorbs lightActivates signal transduction cascade leading to graded changes in membrane potential and Nt releasePhotoreceptive organsStructures specialized for light detection, encode direction, intensity of light, and contrastDiversity of photoreceptive organsFig. 6.35/7.37
The Visible SpectrumPhotoreceptors respond to a small portion of electromagnetic spectrum (300-1000nm)Visible spectrum (humans): 350-750nmVariable in other speciesPhotoreceptors evolved in aquatic ancestors Light attenuates in waterOnly some wavelengths penetrate into water columnFig. 6.27/7.29
Photoreceptor ClassesRhabdomeric PhotoreceptorsApical surface contains photopigments in microvillar projectionsCiliary PhotoreceptorsSingle cilium projection from cell body Ciliary membrane often highly folded into lamellae or disks containing photopigments→ Distinct signal transduction mechanismsLamb et. al. 2007 Fig. 3
Photoreceptor DiversityMany invertebrates: Rhabdomeric photoreceptorsVertebrates: Two types of ciliary photoreceptorsFig. 6.28/7.30
Ciliary Photoreceptors: Rods and ConesOuter segment connected to inner segment by ciliumOuter segment composed of a series of membranous discs filled with photopigmentsInner segment connects to synaptic terminals synapse with other cellsRod and cones structural and functional differences# Photopigments expressedRoles in dim vs bright lightPosition on the retinaFig. 6.29/7.31
Rods and ConesRodsHave slower responsesIntegrate stimulus over a longer periodHave more photopigment than conessensitive to very dim lightsaturate at relatively low light intensity

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