The sence and human ppt for student education

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1. The Special Senses
Touch
Dr. BinuBabu
Asso. Professor
Mrs. JincyEalias
Assi. Professor

2. Introduction
Touchisaperceptioncausingfromtheactivationof
neuralreceptorsintheskin,hairfollicles,tongue,throat,
andmucosa.Avarietyofpressurereceptorsrespondto
variationsinpressure.
Tactileanesthesia:isthelossorimpairmentoftheability
tofeeltouch
Paresthesia:itisasensationoftingling,pricking,or
numbnessoftheskinthatmayresultfromnervedamage
andmaybepermanentortemporary.

3. Touch:Theskin-basedreceptorsystem.Theentire
surfaceofthebodyonwhichthereislivingtissue(skin)is
apotentialreceptivesurfaceforthetouchsystem.
Themostactiveandsensitivepartofthisreceptivefield
arethehands.
Haptics:activeexploratorytouchstrategiesforacquiring
informationfromanobject.
Hapticsincludesnotonlytouchinformationbutalso
kinesthesis

4. Types of sensory nerves

5. Classifications of touch
sensations
Painornociception:Signalsnerveandothertissue
damage.
Balanceorequilibrioception:Allowsthesensingof
bodymovement,direction,andacceleration,andto
attainandmaintainposturalequilibriumandbalance.
Bodyawarenessorproprioception:Providesthe
parietalcortexofthebrainwithinformationonthe
relativepositionsofthepartsofthebody.

6. Temperaturesensingorthermoception:
Thesensationofheatandtheabsenceof
heat.
Interoceptivesenses:ifalsoconsidered,
sensationcanbeexpandedtoinclude
stretchoxygenandcarbondioxide
sensing,pHsensing,andetc.

7. Measuring touch sensitivity
VonFreyhairs:smallhairs,likethosefoundonapaint
brush,ofvariousdiameterarepressedagainstdifferent
partsofthebodytoseeifitisfelt.Thethickerthe
diameterhairneededtogetaresponse,theless
sensitivethearea.
Differentpartsofthebodyvaryinsensitivitytotouch,
lipsandhandsarehighlysensitive,backandbuttocks,
muchlessso.Furthermore,foranyareaofbody,
femalestendtobemoresensitivethanmales.

8. Measuring touch sensitivity
Twopointthresholds:alittledifferent
procedure,butsamegeneralresults.Acompass-
typeinstrumentisusedwhichhastwo
adjustablepoints,pointscanbesetadifferent
distancesfromeachother.Sensitivityis
measuredbydetermininghowfarapartpoints
mustbesentbeforesub.candetectthatthereare
twopointsstimulatingskin,notone.

9. Physiology of touch
Skinreceptors:atvariousdepthsundertheskinarethe
mechanoreceptors,whichstarttheprocessofanalyzingskin
sensationsbyrespondingtoindentationorpressureonthe
skin.
Inorderofdepth,nearesttosurfacetodeepest:
MeisnnerCorpuscles:givestrongestresponsetotransient
stimulationsuchasafingerrubbingoverasurface.RA-P
MerkelDisks:givestrongestresponsetosteadypressureby
smallobject.SA-P
RuffiniEndings:givegreatestresponsetofairlystrong,steady
pressure.Arealsoquitesensitivetomovementswhichresultin
stretchingofskin.SA-D.
PacinianCorpuscles:respondbesttoinitiationandtermination
ofdiffusedpressureagainstskin.RA-D

11. Physiology of touch
NerveFibers:afferentfiberstravellingfromskinreceptorstospinand
(forsome)eventuallybrain.Thesefibersareoffourdistinctcategories.
SlowAdapting:fiberswhichcarrymessagesaboutsteadypressureon
skin.NotsurprisinglythesefibersareconnectedtoMekeldisksand
RuffiniEndingsinskin.
RapidAdapting:carrymessageabouttransientpressurechangeson
skin.connectedtoMiessnerandPacinianCorpuscles.
Punctatefibers:oneswithdistinctreceptivefields(connectto
Miessner&Merkel)
Diffusefibers:oneswithlessdisctictreceptivefields.(connectto
Ruffini&Pacinian).
Combinationofthesefourtypesproducefourtypesofnervefibers.

12. Touch pathways
Touchpathwayrunsupdorsal
(back)ofspinalcolumn.Some
connectwithinterneuronsand
motorneuronsandmediate
reflexivearcs.2mainpathways:
Lemniscal(red;newer)more
sophisticatedaspectsoftouch.
Spinothalamic(older;blue)painand
temperature.

13. Somatosensorycortex
Thesomatosensorycortex
isaregionofthebrainwhich
isresponsibleforreceiving
andprocessingsensory
informationfromacrossthe
body,suchastouch,
temperature,andpain.

14. Pain perception
Painservesanimportant
adaptivefunction–italertsthe
organismtopotentialtissue
damageandcompelswithdraw
ofaffectedareafrompain
source.
Chronicpain,however,often
makeslifemiserableforthose
afflicted.
Nociceptors:freenerveendings
thatsignalpain.Twolocations:
skinsurface–temperature;
Subcutaneous fatlayer:
punctures.

15. Nerve fibers

16. Pain fibers
Adelta:myelinated;fastresponding;sharp,
acute;thermalpain
C-type:slowresponding;buildingpain;
mechanical;thermal;chemical

17. Gate control theory of pain
Tcellssendpainmessage.When
onlyfast(A-beta;A-alpha)fibers
active;nopain.Inhibitorymessage
sendfromSGtoTcells.Whenboth
fastandslow(C-fibers)respond,
SGcellsareinhibitedfromsending
theirinhibitorymessagetoTcells,
Tcellsfireandpainmessageis
sent.
Notealso:T’scanbeinhibitedby
top-downmessagesfromcortex.
“Meaning”ofpainrelevant.

18. Pain pathway
The stages of pain pathway
Transduction
Conduction
Transmission
Modulation
Perception

19. TRANSDUCTION
Transductionbeginswhenperipheralterminals
ofnociceptive(sensoryreceptorsofpain)
Cfibers
A-delta
(Aδ)fibers
Nociceptivefibersaredepolarizedbynoxious
mechanical,thermal,orchemicalenergy.The
membranesoftheseterminalscontainproteins
andvoltage-gatedionchannelsthatconvert
thermal,mechanical,orchemicalenergyintoan
actionpotential(AP).
Nociceptorterminalsarespreaddensely
throughouttheskin.Theyarefoundlesson
periosteum,joints,tendons,muscles,andleaston
thesurfaceoforgans.

20. CONDUCTION
ConductionofanActionPotentialis
thesecondphaseofnociception.
AnAPgeneratedinnociceptor
terminalsisconductedacrossthe
peripheralprocesstothecentral
processwereitdepolarizesthe
presynaptic terminal. The
presynapticterminalinterfaceswith
anetworkofinterneuronsand
secondorderneuronsinthedorsal
horn.Interneuronscanfacilitateor
inhibittransmissiontosecondorder
neurons

21. Thesenociceptorsprojectsfromthe
trigeminalganglionandentertheCNSatthe
levelofthepons.TrigeminalAðandCfibers
passdownthroughtheponsintothemedulla
wheretheysynapseonsecondorderneurons
whichthenrisetodecussatewithinthepons
andpasstothethalamus.

22. MODULATION
Modulationofnociceptive
transmissionisanadaptive
processinvolvingboth
excitoryandinhibitory
mechanisms. The
responsesofsecondorder
neuronscanbesuppressed
orfacilitateddependenton
importanceoftheevent.

23. PERCEPTION
Perceptionofnociceptivepainisdependantuponneural
processinginthespinalcordandseveralbrainregions.Pain
becomesmorethanapatternofnociceptiveactionpotentials
whentheyreachthebrain.
Actionpotentialsascendingthespinothalamictractaredecoded
bythethalamus,sensorimotorcortex,insularcortexandthe
anteriorcingulatetobeperceivedasanunpleasantsensation
thatcanbelocalizedtoaspecificregionofthebody.
Actionpotentialsascendingthespinobulbartractaredecoded
bytheamygdalaandhypothalamustogenerateasenseof
urgencyandintensity.Itistheintergrationofsensations,
emotionsandcognitionthatresultinourperceptionofpain.

24. References
Acree,T.E.,&Beidler,L.M.(1971).Taste,.Berlin,NewYork,
Springer-Verlag.
PerBrodal.(2010).Thecentralnervoussystem:structure
andfunction.OxfordUniversityPress,Cop.
Nieuwenhuys,R.,JVoogd,Voogd,J.,&ChristiaanVan
Huijzen.(2008).TheHumanCentralNervousSystem.
Springer.