Lecture6

OtherSensorySystems

Cogs17*UCSD

VestibularSystem

Balance

VestibularSysteminInnerEar

InnerEar

Hearing

VestibularSystem

Hearing

Semicircularcanals

Otolith Organs

Semi-CircularCanals- ROTATIONAt0facingX…

X

Y

Z

Semi-CircularCanals

TubesfilledwithK+richEndolymph

HairCells(VestibularReceptorCells)

intheAmpullaeatthebaseofthecanals

Cristaampullaris

Ampulla

Semi-CircularCanals

Cillia of

HairCellsembeddedin

gelatonous Cupula,arebentbyflowofEndolymph

inAmpulla

Cristaampullaris

Semi-CircularCanals

Cillia of

HairCellsembeddedin

gelatonous Cupula,arebentbyflowofEndolymph

inAmpulla

Cristaampullaris

Atstart ofrotation,fluidlagsbehind

Atend ofrotation,fluidovershoots

AsfluidpushesagainstCrista,oneway,ortheother,HairCells firemore,orless

Semi-CircularCanals

Cillia of

HairCellsembeddedin

gelatonous Cupula,arebentbyflowofEndolymph

inAmpulla

Cristaampullaris

Atstart ofrotation,fluidlagsbehind

Atend ofrotation,fluidovershoots

AsfluidpushesagainstCrista,oneway,ortheother,HairCells firemore,orless

Cellsonlyreactatonset andoffset ofmotion,

(oracceleration&deceleration),not duringsteadyrotation

SystemdetectsCHANGE

VestibularHairCalls

• VerysimilartoHairCellsinauditorysystem

• HighconcentrationofPotassium(K+)

inEndolymph

• K+in,Ca++in,Neurotransmitter

released

• BUToneimportantdifference...

VestibularHairCells

…haveSpontaneous firing,inabsenceofinputThatis,whennorotation,HairCellreleasesa

baserateofneurotransmitter

LESSneurotransmitter

isreleased

Bendcilliaotherway,

MOREneurotransmitter

isreleased

Bendcillia oneway,

Baserate

Otolith Organs- HEADTITLT

TheMaculamadeoftheUtricle

andtheSaccule

HairCellslinethewallsofthese

Endolymph-filledchambers

Otolith Organs- HEADTITLT

Otolith

Whicheverangleyoutiltyourhead,someOtoliths willweighdownthecillia ofsomeHairCells

Again,bendoneway,firemore,bendotherway,fireless

Otoliths"EarStones"

calcium-carbonatecrystals,sitingelatinousmaterial

inwhichHairCells areembedded

Whenheadisupright,havebaserateoffiring

Andagain,VestibularSystem

onlydetectsCHANGE

Otolith Organs- HEADTITLT

Notethat AccelerationandDeceleration havesameeffectasTiltBackwardandTiltForward,respectively

So,Otolith Organsdetectstart/stopoflocomotion

aswellasheadtilt

VestibularPathwayHairCells

VestibularGanglion

8thCranialNerve VestibularNuclei(Medulla)

Cerebellum

SuperiorColliculus

CranialNerves3,4,6

(EyeMovements)

TemporalLobe(???)

SpinalCord/BrainStem

(Posture)

Coordinatew/visualmotioninfo

MotionSickness

OccurswhenVestibular andVisual systemsarenotcoordinatedasexpected

Inspace

Inacar

SomatosensorySystem

TheSkinSenses

SomatosensoryReceptors

Pain&TemperatureReceptors

FreeNerveEndings

Mechano-Receptors

EncapsulatedNerveEndings

FreeNerveEndings

Pain&TemperatureReceptors

FreeNerveEndings

TEMPERATURE:

Thermoreceptors(Warm-best&Cool-Best)

PAIN:

Nociceptor(Pain,Itch,Extremesoftemp)

SomatosensoryReceptors

Mechano-Receptors

EncapsulatedNerveEndings

ForTouchand

Proprioception(internalmuscle

andorganmovements)

Mechano-Receptors

SmallReceptiveField1:1forDetails

LargeReceptiveFieldConvergent

Meissner'sCorpusclesSlippage

Merkel'sDiscs

ReadingBraille

PacinianCorpusclesBending

RuffinniEndingsPosture

offon

on off

FastAdapting

SlowAdapting

AcrossFiberCoding

89o73o 105o

Codefor89o :WB =CB

Temperature

ReceptorRespo

nse

Cool-BestReceptors

Warm-BestReceptors

CB WB

Codefor73o:WB <CB

Codefor105o :WB >CB

Thermoreceptors

"PhysiologicalZero"

So,itstherelativeproportionofactivityacrossfibers

thatcodesforagiventemperature

AcrossFiberCoding

89o73o 105o

89o

Temperature

Temperature

ReceptorRespo

nse

ReceptorRespo

nse

Cool-BestReceptors

Warm-BestReceptors

CB WB

CB

WB Afteradaptingtoicecoldwater

89o ismiscoded as105o

(WB >CB)

Feelswarm!

Thermoreceptors

Cool-BestReceptortemporarilyadapted

T

EncapsulatedNerveEnding

BRAIN

SPINALCORD

LeftVPN

Medulla

MedialLemniscal

Left CortexS1

MedialLemniscalPathway

FreeNerveEnding

SpinalThalamicPathway

Cross-overInSpinalCord

Cross-overInMedulla

EnterthroughDorsalHornofSpinalCord

SomatosensoryPathways

VPN(VentralPosteriorNucelus)

ofThalamus

T

EncapsulatedNerveEnding

VPNRightLeftVPN

Medulla

MedialLemniscal

Left CortexS1 S1CortexRight

FreeNerveEnding

SpinalThalamicPathway

Cross-overInSpinalCord

Cross-overInMedulla

MedialLemniscalPathway

Brown-SequardSyndrome

Damagetoonlyonesideofspinalcord>>

LossofTouch onIPSI-Lateralside

LossofTemp/PainonCONTA-Lateralside

BRAIN

SPINALCORD

SomatosensoryPathways

VPNVPN

MedullaMedial

Lemniscal

CortexS1 S1Cortex

TSpinalThalamic

PathwayMedialLemniscal

Pathway

BRAIN

SomatosensoryPathways

T

S2CortexCortexS2 CorpusCallosum

FromS2 on,infofromboth

sidesiscombined

Somatonsensory CortexPENFIELDMAP

TOPOLOGICALMAPS(PreservetheSpatialRelationships

of sensorysurface)

MAGNIFICATION(Hands&Mouth

Highacuity=detaildiscrimination)

T

Itch

Scratch

Gate1

BRAIN

SPINALCORD

LeftVPN

LCortexS1

GateTheoryofendogenousPAINcontrol

ToMedulla

SGCell

InhibitoryInter-NeuroninSpinalCord

T

Itch

Gate2

BRAIN

SPINALCORD

LeftVPNMidbrain

PAG

HindbrainRaphe

LCortexS1

GateTheoryofendogenousPAINcontrol

Endorphinsreleased

SGCell

InhibitoryInter-NeuroninSpinalCord

GateTheory- InBrainInbrain,

activityalongPainpathways

ProvokesactivityfromEndorphincells

ReceptorsitesonTerminal ofpaincellrespondstoEndorphins

InhibitsreleaseofSubstanceP

GateTheoryofendogenousPAINcontrol

Endorphinsreleased

SubstancePreleased

Gate3