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Chapter 35SensesSensesPerceive environmentFind foodAvoid predatorsAvoid dangerFind shelterInteract sociallySensory ReceptorsMechanoreceptorsTouch, hearing, equilibrium, pressureThermoreceptorsRadiant energy, infraredNociceptorsPain ChemoreceptorsSmell, tasteOsmoreceptorsWater, solute concentrationPhotoreceptorsLight, vision

Sensory ReceptorsSensory receptorNerve pathwayBrain integrationSensory perception

Sensory ReceptorsReceptors specific for given stimulusStrong stimulationGreater frequency of action potentialsGreater number of neuronsSensory adaptaionFrequency of AP decrease or stop w/ constant simulusSomaticStart at sensory neuronsDifferent sensors to different part of brainSomatosensory cortex

SomaticBody surfaceFree nerve endingsMeissner corpusclesPacinian corpusclesThermoreceptorsBulb of KrauseRuffini endings

SomaticMusclesMechanorecptorsMotionPosition in spaceStretch

SomaticPainperception of injuryNociceptorsSomaticskin, skeletal muscle, joints, tendonsVisceralinternal organsFewer nocieptorsReferred painCell damage releases bradykininsBradykinins stimulate nearby nociceptorsStimulus perceived by brain as painOlfactionSmellSocial communicationFind matesFind preyAvoid predators

OlfactionWell-developed in most mammalsEspecially carnivores & ungulatesNon-existent in cetaceans (whales, dolphins, etc.)Canines 100,000-1 million times better than humansBloodhounds 10-100 million times

OlfactionPoorly developed in most birdsWell-developed in fishSalmonID and return to home streamsCatfishID others, maintain social order

OlfactionChemicals inhaledMust be dissolved in liquid (mucus)Binds to membrane proteinsTriggers depolarization of neuronsDifferent combinations of receptor activation recognized as patterns by brain

Olfaction

OlfactionPheromonesAir-borne chemical that triggers behavioral response in same speciesAlarmFood trailSexTerritorialTasteDifferentiate nutrition vs. noxiousReceptors on various organsAntennaeTentaclesTongueLegs

TasteFive tastes in humansSweetSourSaltyBitterUmami

ChemoreceptorsAntennaeMost arthropodsMultiple functionsSmell & taste most importantAlso touch, air motion, vibration, heatOlfactory receptors bind to odor moleculesSends signal to antennal lobe in brain

ChemoreceptorsVomeronasal organMany animals (including humans)Certain smellsMany pheromonesMay be involved in triggering some aggression & mating

ChemoreceptorsVomeronasal organFlehmen responseIn catIn deer

HearingDetect vibrationsInterpret as soundAmplitude (loudness)Frequency (pitch)Important for communicationImportant for finding preyImportant for avoiding predators

HearingSonichuman frequencies15 Hz-20,000 HzBest at 2,000-4,000 HzUltrasonicabove human frequenciesBats, dogsSubsonicbelow human frequenciesSnakes (sense through bellies)Whales, giraffes, elephants (communication)HearingExternal ear (pinna)Collects soundMiddle earOssiclesMalleus (hammer)Incus (anvil)Stapes (stirrup)Receive vibrations from tympanum (eardrum)Transmit to inner earInner earCochleaauditory nervesSemicircular canalsbalance

Hearing,,,

HearingVibrations coming down ear vibrate ossiclesStapes vibration pushes on oval membrane on cochleaFluid in cochlea moves at specific frequencyFluid wave moves tectorial membraneMovement of tectorial membrane stimulates nerve impulse

Hearing,,,

HearingEquilibriumVestibular organs (semicircular canals)Static equilibriumLinear movement of headOtolithic membrane movement triggers hairsDynamic equilibriumRotation, acceleration, decelerationFluid bends hairs in crista ampullaris

HearingEcholocationDolphis, shrews, bats, most whalesActive sonarSounds sent outHear reflection of sounds (echo)Able to triangulate sounds

HearingLateral lineDetect vibrations in waterAlong sides of many fishSimilar to certain aspects of hearing & equilibrium

VisionPhotoreceptorsPart of brain that can interpret pattern of nerve impulsesPigment molecules absorb incoming photonsConvert photons into action potential

VisionInvertebrateSimplePhotosensitive receptorsDo not form imagesLight & darkOcellus

VisionInvertebrateCompoundArthropodsMultiple facetsEach has own lens & photoreceptor cellsVery sensitive to motion360o field of visionMultiple images integrated in brainPoor image resolution

VisionInvertebrateMollusksMany have lens eyes (similar to vertebrates)Cephalopods have most developedHunters, 3 dimensions, often move fast

VisionVertebrateOuter layerScleraCorneaMiddle LayerLensIrisPupilChoroidAqueous HumorVitreous Humor

VisionInner layerRetinaMacula luteaOptic discTapetum Lucidum

VisionRodsLow lightNight visionNo colorConesBright lightDay visionColor

VisionAccommodationthe process by which an eye changes to keep an object in focus as it moves closer or further away.Fish, reptilesLens moves forwards & backwards in eyeBirds, mammalsciliary muscles change shape of lens.

VisionPhotons enter through corneaAre focused by lensAbsorbed by cells in retinaPhoton activity stimulates receptors to generate action potential

VisionEye placementForward-facingPredatorsDepth perceptionSide-facingPreyWide field of vision

Other SensesElectroceptionDetect electrical fieldsSharks, skates, raysLungfish, coelacanths, sturgeonsMonotremes (especially platypus)Activegenerate own fieldElectric eels & fishCommunicationPassivesense other fieldsChondrichthyes

Other SensesMagnetoceptionMostly birdsVery important to migrationSome beesDetect magnetic fieldsMagnetiteFound in many rocks & mineralsSource of iron oreIdentified in brains of birds, bees, and humansWhen magnetite aligns w/ Earths magnetic field, stimulates nerve impulsePoorly understood sense