-
8/7/2019 Handouts Special Senses Sp11 BIO 160
1/8
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
-
8/7/2019 Handouts Special Senses Sp11 BIO 160
2/8
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
-
8/7/2019 Handouts Special Senses Sp11 BIO 160
3/8
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
-
8/7/2019 Handouts Special Senses Sp11 BIO 160
4/8
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
-
8/7/2019 Handouts Special Senses Sp11 BIO 160
5/8
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
-
8/7/2019 Handouts Special Senses Sp11 BIO 160
6/8
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)
-
8/7/2019 Handouts Special Senses Sp11 BIO 160
7/8
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
-
8/7/2019 Handouts Special Senses Sp11 BIO 160
8/8
OrgansofHearing OrganofCorti
o Locatedwithinthecochleao
Receptors=haircellsonthebasilarmembraneo
Gelliketectorialmembraneiscapableofbendinghaircellso
Cochlearnerveattachedtohaircellstransmitsnerveimpulsestoauditorycortexontemporallobe
MechanismofHearing Vibrationsfromsoundwavesmovetectorialmembrane
Haircellsarebentbythemembrane
Anactionpotentialstartsinthecochlearnerve
Continuedstimulationcanleadtoadaptation
