Special SensesAdaptationVisual PathwaysSlide 4Slide 5Retinal Processing: Receptive Fields of Ganglion CellsSlide 7Thalamic ProcessingCortical ProcessingThe Ear: Hearing and BalanceSlide 11Outer EarSlide 13Middle Ear (Tympanic Cavity)Slide 15Ear OssiclesSlide 17Inner EarSlide 19The VestibuleSlide 21The Semicircular CanalsSlide 23The CochleaSlide 25Slide 26Slide 27Slide 28Sound and Mechanisms of HearingProperties of SoundSlide 31Slide 32Transmission of Sound to the Inner EarSlide 34Resonance of the Basilar MembraneSlide 36The Organ of CortiExcitation of Hair Cells in the Organ of CortiSlide 39Auditory Pathway to the BrainSimplified Auditory PathwaysAuditory ProcessingDeafnessMechanisms of Equilibrium and OrientationAnatomy of MaculaeSlide 46Effect of Gravity on Utricular Receptor CellsSlide 48Crista Ampullaris and Dynamic EquilibriumActivating Crista Ampullaris ReceptorsRotary Head MovementBalance and Orientation PathwaysCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsSpecial SensesSpecial senses – Ear – auditory and balanceCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsAdaptationAdaptation to bright light (going from dark to light) involves:Dramatic decreases in retinal sensitivity – rod function is lostSwitching from the rod to the cone system – visual acuity is gainedAdaptation to dark is the reverseCones stop functioning in low lightRhodopsin accumulates in the dark and retinal sensitivity is restoredCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsVisual PathwaysAxons of retinal ganglion cells form the optic nerve Medial fibers of the optic nerve decussate at the optic chiasmMost fibers of the optic tracts continue to the lateral geniculate body of the thalamusOther optic tract fibers end in superior colliculi (initiating visual reflexes) and pretectal nuclei (involved with pupillary reflexes)Optic radiations travel from the thalamus to the visual cortexCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsVisual PathwaysFigure 15.23Copyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsVisual PathwaysSome nerve fibers send tracts to the midbrain ending in the superior colliculiA small subset of visual fibers contain melanopsin (circadian pigment) which:Mediates papillary light reflexesSets daily biorhythmsCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsOn-center fieldsStimulated by light hitting the center of the fieldInhibited by light hitting the periphery of the fieldOff-center fields have the opposite effects These responses are due to receptor types in the “on” and “off” fieldsRetinal Processing: Receptive Fields of Ganglion CellsCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsFigure 15.24Retinal Processing: Receptive Fields of Ganglion CellsCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsThalamic ProcessingThe lateral geniculate nuclei of the thalamus:Relay information on movementSegregate the retinal axons in preparation for depth perceptionEmphasize visual inputs from regions of high cone densitySharpen the contrast information received by the retinaCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsCortical ProcessingStriate cortex processes Basic dark/bright and contrast informationPrestriate cortices (association areas) processesForm, color, and movement Visual information then proceeds anteriorly to the:Temporal lobe – processes identification of objectsParietal cortex and postcentral gyrus – processes spatial locationCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsThe Ear: Hearing and BalanceThe three parts of the ear are the inner, outer, and middle earThe outer and middle ear are involved with hearingThe inner ear functions in both hearing and equilibriumReceptors for hearing and balance: Respond to separate stimuliAre activated independentlyCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsThe Ear: Hearing and BalanceFigure 15.25aCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsOuter EarThe auricle (pinna) is composed of:The helix (rim)The lobule (earlobe)External auditory canalShort, curved tube filled with ceruminous glandsCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsOuter EarTympanic membrane (eardrum)Thin connective tissue membrane that vibrates in response to soundTransfers sound energy to the middle ear ossicles Boundary between outer and middle earsCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsMiddle Ear (Tympanic Cavity)A small, air-filled, mucosa-lined cavity Flanked laterally by the eardrumFlanked medially by the oval and round windowsEpitympanic recess – superior portion of the middle earPharyngotympanic tube – connects the middle ear to the nasopharynxEqualizes pressure in the middle ear cavity with the external air pressureCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsMiddle Ear (Tympanic Cavity)Figure 15.25bCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsEar OssiclesThe tympanic cavity contains three small bones: the malleus, incus, and stapesTransmit vibratory motion of the eardrum to the oval windowDampened by the tensor tympani and stapedius musclesCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsEar OssiclesFigure 15.26Copyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsInner EarBony labyrinthTortuous channels worming their way through the temporal boneContains the vestibule, the cochlea, and the semicircular canalsFilled with perilymphMembranous labyrinthSeries of membranous sacs within the bony labyrinthFilled with a potassium-rich fluidCopyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsInner EarFigure 15.27Copyright © 2004 Pearson Education, Inc., publishing as Benjamin CummingsThe VestibuleThe central egg-shaped cavity of the bony labyrinthSuspended in its perilymph are two sacs: the saccule and utricleThe saccule extends into the cochleaThe utricle extends into the semicircular canalsThese sacs:House equilibrium receptors called