exercise 3 sensory functions

8/9/2019 Exercise 3 Sensory Functions

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SENSORY PATHWAYS IN

MAN


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Olfactory sensations

CHAMBER TIME (sec)

Lower 8

Upper 55

Time it too for t!e smell to "e#etecte#


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• The distance of the odoriferous substance tothe receptors determines the strength of theperceived odor.

• Concentration of odorant substance was high,thus more of the substance binds to thereceptors

• The substance must be sli$!tly %ater

sol&"le so it can pass thru the mucus• The substance must be sli$!tly li'i#

sol&"le because lipid constituents of ciliumare weak barrier to non-lipid-soluble odorants


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Olfactory a#a'tation

SBSTANCE

TIME(sec)

REMAR* S

herb !ungent

perfume " #trong

food 5$ %ppeti&ing

Time it too for t!e smell of t!e#i+erent s&"stances to #isa''ear


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• %daptation refers to the state in w

hicholfactor' neurons have ceased to bestimulated b' odorant substances

after a few minutes of full e(posure.• )lfactor' receptors are known to

adapt to a degree of around 5*+ after

$ second or so after stimulation• )lfactor' adaptation

– ierences in glomeruli


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/u'ton and 0all,


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• Least understood of all the senses

• #mell and taste classi3ed as visceral

senses• 4oth taste and smell receptors are

c!emorece'tors• #timulated b' molecules in solution in

mucus in nose and saliva in mouth


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ader,**$2


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/anong, **62

/u'ton and 0all,


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/u'ton and 0all,


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• #ignal transduction• )dorant substance came in contact with

olfactor' membrane

• #ubstance diused into mucus membrane• #ubstance bound to a portion of the receptor

proteins in cilium membrane• 7eceptor proteins threads thru the membrane

several times folding inward and outward• O#orant binds to the receptor protein that folds

outward

• ,-'rotein found on the inside of the folding protein


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• /-proteins were e(cited, dissociating thealpha subunit

• %lpha subunit activated a#enylyl cyclase,

attached to the inside of the ciliar'membrane

• %den'l'l c'clase converted ATP to cAMP

• c%! activated nearb' sodium channels,

opening them• %ction potential was transmitted into the

C# b' means of the olfactor' n%Cervesmell pathwa' has no rela' in the thalamus


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,&statory Sensations

• Taste is mainl' a function of the tastebuds in the mouth

/u'ton and 0all,**12


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• !rimar' sensations• #weet 9 sugars, gl'cols, alcohols,

aldeh'des, ketones, amides,

esters, some amino acids, somesmall proteins, sulfonic acids,halogenated acids, or inorganic

salts of lead and ber'llium• #our 90:, this is wh' all acids

taste sour

•

4itter 9 evoked b' alkaloids


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Area ofton$&e

S%eet Salty So&r Bitter

Tip : ; ; ;

#ides ; : : :

4ack ; ; ; :

Table


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#chaum,


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• Taste t!res!ol# 9 the minimumamount a substance in order to

perceive a stimulus whether pleasantor unpleasant• ierent values for dierent substances

• %ccording to espopoulous and#ilbernagl **62 the taste threshold fortable sugar is $*- mol=L


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.orm of s&$ar Time taste# (secon#)

Cr'stals $6

solution 6

Table


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.oo# Place# onton$&e

C!e%in$(close#

nostrils)

C!e%in$(o'en

nostrils)Carrot - - :

4anana - - :

!otato - - :

)nion - : :

Table


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• The sense of taste is in@uenced greatl'b' the sense of smell.

• The gustation and olfaction worktogether to let the cerebral corte(interpret a certain stimulus.

• #ome particles of the odorants move tothe mouth region and e(cite the taste buds

present ader, **


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T%#TA 4U#• Composed of 5* modi3ed epithelial

cellsB sustentacular and taste cells

T%#TA CALL#• invaginated with microvilli, taste

nerve 3bers and vesicles containingneurotransmitters fpr e(citation ofnerve endings for taste stimuulation


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T%#TA 4U#• Composed of 5* modi3ed epithelial cellsB

sustentacular and taste cells

• Tongue, palata, tonsillar pillars, epiglottis anduppermost regions of phar'n(

T%#TA CALL#• evaginated with microvilli, taste nerve 3bers

and vesicles containing neurotransmitters fore(citation of nerve endings for tastestimulation


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• #ignal transduction

• taste chemical binds to a protein

receptor molecule l'ing on theouter surface of the microvilli


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/u'ton and 0all,


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• !athwa'• Taste receptors from the anterior =6 of the tongue

generate action potential that pass thru the$. lingual node,

. chorda t'mpani6. facial nerve, C DD

/0 Tract&s solitari&s

• !osterior $=6 of the tongue, circumvallate papillae2.%! transmitted thru

$. /lossophar'ngeal nerves, C DE10 Tract&s solitari&s

• 4ase of tongue•. agus nerve, C E

•. Tract&s solitari&s


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• !athwa'

• ote that all taste 3bers s'napse at thenuclei of the tract&s solitari&s

• #econd order neurons were sent to 2entral'osterior me#ial n&cle&s of the thalamus

• third order neurons were transmitted tothe lower tip of the 'ostcentral $yr&s in

'areital cere"ral corte3• perception was formed, identi3cation of the

taste bitter, sweet, sour, or salt'2


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P!otorece'tion

S&"4ec

tA$e

Blin#s'ot

(mm)

5is&alCon2er$en

ce (mm)

Near Point

Acommo#ation

(mm)

Left e'e7ight

e'e

R&"en $F 55 F5 5 5

An$el * 65 $** $5 6*

6a#e $F


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P&'illary Re9e3

Con#itionsSi:e of

A'ert&re

Wit! li$!t pupil constricted

Wit!o&t pupil dilated

Ta"le 10 C!an$es in t!e a'ert&re of t!eeye in res'onse to t!e 'resence ora"sence of li$!t0


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O'tical 'at!%ay

• !hotoreceptorsB

7ods 9 sensitive to dim light

scotopic vision2 - photoreceptive

pigmentB rhodopsin

Cones 9 sensitive to brightlight photopic vision2 andcolor vision

- photoreceptivepigmentB opsin


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O'tical 'at!%ay

• light cornea pupil

lens light ra's are refracted2 retina rods and conesnerve cells2 optic nerve optic chiasma opticnerves cross2 optic tracts occipital lobe of the brain


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#ignal Transduction

• rod e(posed to light

• r!o#o'sin decomposes, decreasesthe rod membrane conductance forsodium ions in the outer segment ofthe rod

• results to increase# negativit' of

rod membrane potentialh'perpolari&ation2 completeopposite of depolari&ation.


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#ignal Transduction

• Transmits signals to the ple(iformla'er where it s'napses with thebipolar and hori&antal cells

• bipolar cells transmit signals to theinside of the inner ple(iform la'er,where s'napse with the ganglion

cells and amacrine cells• /anglion cells transmit impulse from

retina to the optic nerve


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)ptic isk

• a(ons of ganglion neurons e(tend posteriorl'to a small patch of the retina

• devoid of an' receptors

– site where a(ons are formed into bundlesand e(it as the optic nerve BLIND SPOT

• THIS REGION IS VOID OF

PHOTORECEPTOR NEURONS –light cannot be perceie!

»no i"p#l$e con!#ction no i"age


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7efraction

• when light travels through atransparent medium of dierentdensit', like water – light bends

• four refracting media of the e'e – cornea

– aGueous humor – lens

– vitreous humor


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7efraction

• bent light ra's verge –

forms an image at the retina

D#D)• lens adHust for distance in order to

focus on the retina –

an' adHustments of image in the retina %CC))%TD)


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ear !oint %ccomodation

• the closer an image to the e'e theLA# curve more lightadHustments on the retina

• there is such a distance betweenobHect and light which is of the limitsof the contraction of the ciliar'

muscles bound to suspensor'ligaments to the lens – I%&GE BEGINS TO BLUR


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)ther %CC))%TD) mechanisms

• sometimes, lens move toward theback of the e'e turning inside the

nose C)A7/ACA – !ilation or con$triction

• IL%#0D/ )I LD/0T

C)#T7DCTD)• %7J AT. DL%TD)


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!U!DLL%7K C)#T7DCTD)and DL%TD)

• #K!%T0ATDC and !%7%#K!%T0ATDC

# – controls pupillar' sphincter muscle

• signals through them sent to the e'e via T0D7 C7%D%L A7A from T0D7 A7AUCLAU# D T0A 47%D #TA


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light strikesretina

impulses fromoptic nerves

pre-tectal nuclei

secondar'impulses passthru Adinger-

estphalnucleus

C)#T7DCTD)

)I T0A D7D#


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/u'ton and 0all,


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D#U%L IDAL

• entire vision that one sees out ofeach e'e

• bundles in certain regions of the e'ecan be determined b' mapping the3eld of vision for each e'e

PERI%ETR' • assessed b' /oldmann !erimeter


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/oldmann !erimeter•

subHect is allowed to stare at thecenter with one e'e closed

• small obHect or light is moved slowl'

from peripher' to center of visionfrom man' directions

• subHect indicates whether light isseen or not from the corner of thee'e

• blind spots can be assessed usingthe test


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A;ITORY

SENSATIONS

A%7 %D7C)UCTD)

4)AC)UCTD)

LAIT : ::

7D/0T : ::

ble


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• Anerg' that activates sensor'receptors is known as stim&l&s

• The process b' which a stimulus istransformed to an electricalresponse known as stim&l&strans#&ction.

#timulus transduction involves theopening or closing of ion channels


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• #ounds through 4)A# has /7A%TA7

DTA#DTK due to the #0)7TA7 LA/T0 ofpath that the auditor' stimulus has totravel.

neural pathwa' to auditor' corte( ofbrain

inner ear

auditor' ossicles

mastoid process


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T07)U/0 %D7C)UCTD)

pinnae(ternalauditor'meatus

t'mpanicmembra

ne

auditor'ossicles

inner ear

neuralpathwa'

to reachauditor'corte( ofthe brain


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• vestibular nervesend signals to thebrain to maintainbalance

%wkward bod'positions and

sudden

movements

• needs to correct

its position thus,the bod'movements

brain send

signals to theleft and rightpart of the

bod'

AC0%D#


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CTANEOS

SENSATIONS

The skin is consists ofB• free somatic sensor' nerve endings-nociceptors pain2 and thermoreceptorstemperature2

• erkel Andings- mechanoreceptors, pressure and vibrationreceptors


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•!acinian Corpuscles-tactile receptor

•7uMni Corpuscles- mechano-reception in tension of collagen3bers


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• 7AIA77A !%D

- acuit' of pain in a part of the bod')T C)ACTA I7) T0A T7UA#)U7CA of the pain

- there are connections e(istingbetween dierent neurons comingfrom dierent parts of the bod'.


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all the sGuares had felt the

sensation for all stimuli

• #patial summation

- phenomenon b' which the increasingsignal strength is transmitted b' usingprogressivel' greater numbers of 3bers

exercise 3 sensory functions

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