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8/7/2019 Handouts Special Senses Sp11 BIO 160
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BIO160HandoutsSpecialSensesPartITasteandSmellTheSenses Generalsensesoftouch
o Temperatureo Pressureo Pain
Specialsenseso Smello Tasteo Sighto Hearingo Equilibrium
ChemicalSenses:TasteandSmell Bothsensesusechemoreceptors
o Stimulatedbychemicalsinsolutiono Tastehasfourtypesofreceptorso Smellcandifferentiatealargerangeofchemicals
BothsensescomplementeachotherandrespondtomanyofthesamestimuliOlfactionTheSenseofSmell
Olfactory
receptors
are
in
the
roof
of
the
nasal
cavity
o Neuronswithlongciliao Chemicalsmustbedissolvedinmucusfordetection
Impulsesaretransmittedviatheolfactorynerve Interpretationofsmellsismadeinthecortex
TheSenseofTaste Tastebudshousethereceptororgans Locationoftastebuds
o Mostareonthetongueo Softpalateo Cheeks
Thetongueiscoveredwithprojectionscalledpapillae Tastebudsarefoundonthesidesofpapillae Gustatorycellsarethereceptors
o Havegustatoryhairs(longmicrovilli)o Hairsarestimulatedbychemicalsdissolvedinsaliva
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TasteSensations Sweetreceptors(sugars)
o Saccharineo Someaminoacids
Sourreceptorso Acids
Bitterreceptorso Alkaloids
Saltyreceptorso Metalions
SpecialSensesPartIITheEyeandVisionThe
Eye
and
Vision
70%ofallsensoryreceptorsareintheeyes Eacheyehasoveramillionnerve
fibers
Protectionfortheeyeo Mostoftheeyeisenclosed
inabonyorbit
o Acushionoffatsurroundsmostoftheeye
AccessoryStructuresoftheEye Eyelidsandeyelashes Conjunctiva Lacrimalapparatus ExtrinsiceyemusclesAccessoryStructuresoftheEye Eyelidsandeyelashes
o Tarsalglandslubricatetheeyeo Ciliaryglandsarelocatedbetweenthe
eyelashes
Conjunctivao Membranethatlinestheeyelidso Connectstothesurfaceoftheeyeo Secretesmucustolubricatetheeye
Functionofthelacrimalapparatuso Protects,moistens,andlubricatestheeyeo Emptiesintothenasalcavity
Propertiesoflacrimalfluido Dilutesaltsolution(tears)o Containsantibodiesandlysozyme
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Extrinsiceyemuscleso Sixmusclesattachtotheoutersurfaceoftheeyeo Produceeyemovements
StructureoftheEye Layersformingthewalloftheeyeball
o Fibrouslayer Outsidelayer
o Vascularlayer Middlelayer
o Sensorylayer Insidelayer
StructureoftheEye:TheFibrousLayer Sclera
o Whiteconnectivetissuelayero Seenanteriorlyasthewhiteof
theeye
Corneao Transparent,centralanteriorportiono Allowsforlighttopassthrougho Repairsitselfeasilyo Theonlyhumantissuethatcanbe
transplantedwithoutfearof
rejection
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StructureoftheEye:VascularLayer Choroidisabloodrichnutritivelayerinthe
posterioroftheeye
o Pigmentpreventslightfromscattering Modifiedanteriorlyintotwostructures
o Ciliarybodysmoothmuscleattachedtolens
o Irisregulatesamountoflightenteringeye
Pigmentedlayerthatgiveseyecolor
Pupilroundedopeningintheiris
StructureoftheEye:SensoryLayer Retinacontainstwolayers
o Outerpigmentedlayero Innerneurallayer
Containsreceptorcells(photoreceptors)
Rods
ConesStructureoftheEye:SensoryLayer Signalspassfromphotoreceptorsviaatwoneuronchain Signalsleavetheretinatowardthebrainthroughtheoptic
nerve
Opticdisc(blindspot)iswheretheopticnerveleavestheeyeball
o CannotseeimagesfocusedontheopticdiscStructureoftheEye:SensoryLayer Neuronsoftheretinaandvision
o Rods Mostarefoundtowardstheedgesofthe
retina
Allowdimlightvisionandperipheralvision Allperceptionisingraytones
o Cones Allowfordetailedcolorvision Densestinthecenteroftheretina Foveacentralisareaoftheretinawithonlycones
o Conesensitivity Threetypesofcones Differentconesaresensitivetodifferentwavelengths Colorblindnessistheresultofthelackofoneconetype
o Nophotoreceptorcellsareattheopticdisc,orblindspot
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Lens Biconvexcrystallikestructure Heldinplacebyasuspensoryligamentattachedtotheciliarybody Cataractsresultwhenthelensbecomeshardandopaquewithage Visionbecomeshazyanddistorted EventuallycausesblindnessinaffectedeyeTwoSegments,orChambers,oftheEye Anterior(aqueous)segment
o Anteriortothelenso Containsaqueoushumor
Posterior(vitreous)segmento Posteriortothelenso Containsvitreoushumor
Aqueoushumoro Wateryfluidfoundbetweenlensandcorneao Similartobloodplasmao Helpsmaintainintraocularpressureo Providesnutrientsforthelensandcorneao Reabsorbedintovenousblood
Vitreoushumoro Gellikesubstanceposteriortothelenso Preventstheeyefromcollapsingo Helpsmaintainintraocularpressure
PathwayofLightThroughtheEye Lightmustbefocusedtoapointontheretinaforoptimalvision Theeyeissetfordistancevision
(over20feetaway)
Accommodationthelensmustchangeshapetofocusoncloserobjects(lessthan20feetaway)
PathwayofLightThroughtheEye Imageformedontheretinaisarealimage Realimagesare
o Reversedfromlefttorighto Upsidedowno Smallerthantheobject
ACloserLook Emmetropiaeyefocusesimagescorrectlyontheretina Myopia(nearsighted)
o Distantobjectsappearblurryo Lightfromthoseobjectsfailstoreachtheretinaandarefocusedinfrontofito Resultsfromaneyeballthatistoolong
Hyperopia(farsighted)o Nearobjectsareblurrywhiledistantobjectsareclearo Distantobjectsarefocusedbehindtheretinao Resultsfromaneyeballthatistooshortorfromalazylens
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Astigmatismo Imagesareblurryo Resultsfromlightfocusingaslines,notpoints,ontheretinaduetounequalcurvaturesofthecorneaorlens
HomeostaticImbalancesoftheEyes Nightblindnessinhibitedrodfunctionthathinderstheabilitytoseeatnight Colorblindnessgeneticconditionsthatresultintheinabilitytoseecertaincolors
o Duetothelackofonetypeofcone(partialcolorblindness) Cataractswhenlensbecomeshardandopaque,ourvisionbecomeshazyanddistorted Glaucomacancauseblindnessduetoincreasingpressurewithintheeye
SpecialSensesPartIIIHearingandBalanceTheEar Housestwosenses
o Hearingo Equilibrium(balance)
Receptorsaremechanoreceptors Differentorganshousereceptors
foreachsense
AnatomyoftheEar Theearisdividedintothreeareas
o External(outer)earo Middleear(tympanic
cavity)
o Innerear(bonylabyrinth)TheExternalEar Involvedinhearingonly Structuresoftheexternalear
o Auricle(pinna)o Externalacousticmeatus
(auditorycanal)
Narrowchamberinthetemporalboneo Linedwithskinandceruminous(wax)glandso Endsatthetympanicmembrane
TheMiddleEar(TympanicCavity) Airfilledcavitywithinthetemporalbone Onlyinvolvedinthesenseofhearing Twotubesareassociatedwiththeinnerear
o Theopeningfromtheauditorycanaliscoveredbythetympanicmembraneo Theauditorytubeconnectingthemiddleearwiththethroat
Allowsforequalizingpressureduringyawningorswallowing Thistubeisotherwisecollapsed
BonesoftheMiddleEar(TympanicCavity) Threebones(ossicles)spanthecavity
o Malleus(hammer)o Incus(anvil)o Stapes(stirrip)
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Functiono Vibrationsfromeardrummovethemalleusanvilstirrupinnerear
InnerEarorBonyLabyrinth Includessenseorgansforhearingandbalance Filledwithperilymph Amazeofbonychamberswithinthetemporalbone
o Cochleao Vestibuleo Semicircularcanals
OrgansofEquilibrium Equilibriumreceptorsoftheinnereararecalledthe
vestibularapparatus
Vestibularapparatushastwofunctionalpartso Staticequilibriumo Dynamicequilibrium
StaticEquilibrium
Maculaereceptorsinthevestibule
o Reportonthepositionoftheheado Haircellsareembeddedintheotolithicmembraneo Otoliths(tinystones)floatinagelaroundthehaircellso Movementscauseotolithstobendthehaircells
StructureandFunctionofMaculaeDynamicEquilibrium Cristaampullarisreceptorsinthesemicircularcanals
o Tuftofhaircellso Cupula(gelatinouscap)coversthehaircells
Actionofangularheadmovementso Thecupulastimulatesthehaircellso Animpulseissentviathevestibularnervetothe
cerebellum
Actionofangularheadmovementso Thecupulastimulatesthehaircellso Animpulseissentviathevestibularnervetothecerebellum
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OrgansofHearing OrganofCorti
o Locatedwithinthecochleao Receptors=haircellsonthebasilarmembraneo Gelliketectorialmembraneiscapableofbendinghaircellso Cochlearnerveattachedtohaircellstransmitsnerveimpulsestoauditorycortexontemporallobe
MechanismofHearing Vibrationsfromsoundwavesmovetectorialmembrane Haircellsarebentbythemembrane Anactionpotentialstartsinthecochlearnerve Continuedstimulationcanleadtoadaptation