11 sensory phys · 2018-03-12 · sensory physiology physiology unit 2. sensory pathways in the...

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SENSORY PHYSIOLOGY Physiology Unit 2

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Page 1: 11 Sensory Phys · 2018-03-12 · SENSORY PHYSIOLOGY Physiology Unit 2. Sensory Pathways in the Brain. Sensory System •Sensory information –Conscious sensations –Unconscious

SENSORYPHYSIOLOGY

PhysiologyUnit2

Page 2: 11 Sensory Phys · 2018-03-12 · SENSORY PHYSIOLOGY Physiology Unit 2. Sensory Pathways in the Brain. Sensory System •Sensory information –Conscious sensations –Unconscious

SensoryPathwaysintheBrain

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SensorySystem

• Sensoryinformation– Conscioussensations– Unconscioussensations

• Sensoryprocessing– Transferringstimulusenergyintoagradedpotential(receptorpotential)

– Thentoanactionpotentialinanafferentneuron• Patternofactionpotentialsisthecodethatprovidesinformationonthestimulus

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GeneralClassesofReceptors

• Mechanoreceptors• Thermoreceptors• Photoreceptors• Chemoreceptors• Nociceptors

Page 5: 11 Sensory Phys · 2018-03-12 · SENSORY PHYSIOLOGY Physiology Unit 2. Sensory Pathways in the Brain. Sensory System •Sensory information –Conscious sensations –Unconscious

SensoryReceptors• Specializedendingsof

sensoryneurons• Separatecellsthatsignal

theafferentneuronsbyreleasingchemicalmessengers

• Theenergyorchemicalthatactivatesasensoryreceptorisastimulus

• Theprocessbywhichastimulusistransformedintoanelectricalresponseissensorytransduction

Page 6: 11 Sensory Phys · 2018-03-12 · SENSORY PHYSIOLOGY Physiology Unit 2. Sensory Pathways in the Brain. Sensory System •Sensory information –Conscious sensations –Unconscious

ReceptorPotential

• Sensorytransductioninvolvestheopening/closingofionchannels

Page 7: 11 Sensory Phys · 2018-03-12 · SENSORY PHYSIOLOGY Physiology Unit 2. Sensory Pathways in the Brain. Sensory System •Sensory information –Conscious sensations –Unconscious

GradedPotentialtoActionPotential

• Theinitialionmovementgenerateslocalcurrentthatflowsashortdistancealongtheaxontoaregionwherethemembranehasvoltage-gatedionchannelsananAPcanbegenerated

• UsuallythefirstNodeofRanvier

Page 8: 11 Sensory Phys · 2018-03-12 · SENSORY PHYSIOLOGY Physiology Unit 2. Sensory Pathways in the Brain. Sensory System •Sensory information –Conscious sensations –Unconscious

SensoryModality

• Modalities– Temperature,taste,sound,touch

• Submodalitiesofsensation– Submodalityoftemperature:hot/cold– Submodalitiesoftaste:sweet,bitter,salty,sour,umame

– Submodalityofsound:pitch,volume

Page 9: 11 Sensory Phys · 2018-03-12 · SENSORY PHYSIOLOGY Physiology Unit 2. Sensory Pathways in the Brain. Sensory System •Sensory information –Conscious sensations –Unconscious

PrimarySensoryCoding

• ConvertingstimulusenergythatconveysrelevantsensoryinformationtotheCNSiscoding– Typeofenergyitrepresents(modality)

– Intensity– Locationofthebodyaffected

Sensory Unit

Page 10: 11 Sensory Phys · 2018-03-12 · SENSORY PHYSIOLOGY Physiology Unit 2. Sensory Pathways in the Brain. Sensory System •Sensory information –Conscious sensations –Unconscious

StimulusIntensity

Page 11: 11 Sensory Phys · 2018-03-12 · SENSORY PHYSIOLOGY Physiology Unit 2. Sensory Pathways in the Brain. Sensory System •Sensory information –Conscious sensations –Unconscious

StimulusDuration• Rapidadaptation

– Phasicreceptors– Signalchange– Rapidfadingofsensation– “on” and“off” response

• Slowadaptation– Tonicreceptors– Signalslowchangesor

prolongedevents– Joint,musclereceptorsfor

maintainingposture

Page 12: 11 Sensory Phys · 2018-03-12 · SENSORY PHYSIOLOGY Physiology Unit 2. Sensory Pathways in the Brain. Sensory System •Sensory information –Conscious sensations –Unconscious

SomaticSenses

• 4SomatosensoryModalities1. Touch2. Proprioception3. Temperature4. Nociception

– Pain– Itch

Page 13: 11 Sensory Phys · 2018-03-12 · SENSORY PHYSIOLOGY Physiology Unit 2. Sensory Pathways in the Brain. Sensory System •Sensory information –Conscious sensations –Unconscious

SomaticSensation• Sensationsfrom

– Skin– Muscles– Bones– Tendons– Joints

• Sensationsof– Touch– Pressure– Bodyposition– Temperature– Pain

Page 14: 11 Sensory Phys · 2018-03-12 · SENSORY PHYSIOLOGY Physiology Unit 2. Sensory Pathways in the Brain. Sensory System •Sensory information –Conscious sensations –Unconscious

SensoryPathways• ASensoryPathway

– Abundleofparallel neuronsthatruntogether– Receptoractivation– 1storder(primary)sensoryneuron– 2nd order(secondary)sensoryneuron

– aninterneuron– decussation

– 3rd order(tertiary)sensoryneuron– Alsocalledascendingpathways

– Non-specific– Specific

– Manysensorypathwaysalsosendinformationtothecerebellumtocoordinatebalanceandmovement

– Mostsensorypathwaysconveyinformationfromasinglemodality

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SpecificAscendingPathways• AscendingPathways

1. ThroughtheBrainstem(RAS)2. Thalamus3. Finalneuronsinthepathwayterminateinthe

specificsensoryareaofthecortexandthecerebellum

• Exception:olfactoryneuronsbranchtotheolfactorycortexandamygdala/hippocampus(limbicsystem)ratherthanthethalamus• Odorsarecloselyassociatedwithmemoriesandemotions

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SomatosensorySystemPathwaysAnterolateralPathway

• 1st neurontravelsintothespinalcord

• 2nd neurondecusatesinthespinalcordanduptothethalamus

• 3rd neurontravelstothesomatosensorycortex

• Processes• Nociception• Temperature• Coursetouch

Decusationinthespinalcord

Page 17: 11 Sensory Phys · 2018-03-12 · SENSORY PHYSIOLOGY Physiology Unit 2. Sensory Pathways in the Brain. Sensory System •Sensory information –Conscious sensations –Unconscious

SomatosensorySystemPathwaysDorsalColumnPathway

• 1st neuronpassesintothespinalcordanduptothebrainstemwhereitdecusates

• 2nd neurontravelstothethalamus

• 3rd neurontravelstothesomatosensorycortex

• Processes• Finetouch• Vibration• Proprioception

Decusationinthebrainstem

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DistributionofPeripheralStimuli

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SpecialSense:Vision

• Opticalcomponent– Focusesvisualimageonthereceptorcells

• Neuralcomponent– Transformsthevisualimagetoapatternofgradedandactionpotentials

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Light

• Thereceptorsoftheeyeareonlysensitivetoasmallportionoftheelectromagneticspectrum

• Thevisiblespectrumisbetween400-750nm

• Differentwavelengthsoflightareperceivedasdifferentcolors

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ColorVision

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TheOpticsofVision

• Refractinglightishowoureyesfocusonobjects

• Thecorneaandthelensrefractlighttofocusitintheretina

• Adjustmentsfordistanceismadebychangestheshapeofthelens.Thisisaccommodation

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Accommodation

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PhotoreceptorCells• Outersegmentmadeof

stackedlayersofmembrane(discs).

• Thediscsholdthephotopigments whichabsorblight

• Photopigmentsaremembraneboundproteinscalledopsins whichsurroundandbindamoleculecalledretinal• Retinolisaderivativeof

vitaminA

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PhotoreceptorCells

• Thereare4uniquephotopigments intheretina(calledphotopsins)• Rodshavethephotopigmentrhodopsin

• Theothersarefoundinthe3typescones

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Phototransduction

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NeuralPathwayofVision

• Pathway:– Photoreceptorsoftheretina

– OpticNerve(C.N.II)– Opticchiasm

• SCN

– Optictract– Thalamus– Visualcortex

Suprachiasmaticnucleus(SCN)controlscircadianrhythms

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SpecialSense- Hearing

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SoundTransmission

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OrganofCorti

Sensory Hair Cells

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NeuralPathwayforHearing

• Pathway:– Sensoryhaircells– Cochlearbranchofvestibulocochlearnerve(C.N.VIII,AuditoryNerve)

– Brainstem– Midbrain– Thalamus– Auditorycortex

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VestibularSystem

• Vestibularapparatus– Semicircularcanals

–Utricle– Saccule

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SemicircularCanalsRotationalMovement

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UtricleandSacule• Themaculaprovidesinfoonchangesinheadpositionrelativeto:– Forceofgravity– Linearacceleration

• Vestibularinformationisusedfor:– Controleyemovements– Reflexestomaintainposture

– Consciousawarenessofourselvesin“space”

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Gustation

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Olfaction