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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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Olfactory sensations
• 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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Olfactory a#a'tation
• %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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Olfactory a#a'tation
/u'ton and 0all,
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Olfactory sensations
• 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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Olfactory sensations
ader,**$2
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Olfactory sensations
/anong, **62
/u'ton and 0all,
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Olfactory sensations
/u'ton and 0all,
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Olfactory sensations
• #ignal transduction• )dorant substance came in contact with
olfactor' membrane
• #ubstance diused into mucus membrane• #ubstance bound to a portion of the receptor
proteins in cilium membrane• 7eceptor proteins threads thru the membrane
several times folding inward and outward• O#orant binds to the receptor protein that folds
outward
• ,-'rotein found on the inside of the folding protein
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Olfactory sensations
• /-proteins were e(cited, dissociating thealpha subunit
• %lpha subunit activated a#enylyl cyclase,
attached to the inside of the ciliar'membrane
• %den'l'l c'clase converted ATP to cAMP
• c%! activated nearb' sodium channels,
opening them• %ction potential was transmitted into the
C# b' means of the olfactor' n%Cervesmell pathwa' has no rela' in the thalamus
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,&statory Sensations
• Taste is mainl' a function of the tastebuds in the mouth
/u'ton and 0all,**12
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,&statory Sensations
• !rimar' sensations• #weet 9 sugars, gl'cols, alcohols,
aldeh'des, ketones, amides,
esters, some amino acids, somesmall proteins, sulfonic acids,halogenated acids, or inorganic
salts of lead and ber'llium• #our 90:, this is wh' all acids
taste sour
•
4itter 9 evoked b' alkaloids
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,&statory Sensations
Area ofton$&e
S%eet Salty So&r Bitter
Tip : ; ; ;
#ides ; : : :
4ack ; ; ; :
Table
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,&statory Sensations
#chaum,
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,&statory Sensations
• 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 $*- mol=L
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,&statory Sensations
.orm of s&$ar Time taste# (secon#)
Cr'stals $6
solution 6
Table
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,&statory Sensations
.oo# Place# onton$&e
C!e%in$(close#
nostrils)
C!e%in$(o'en
nostrils)Carrot - - :
4anana - - :
!otato - - :
)nion - : :
Table
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,&statory Sensations
• 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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,&statory Sensations
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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,&statory Sensations
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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,&statory Sensations
• #ignal transduction
• taste chemical binds to a protein
receptor molecule l'ing on theouter surface of the microvilli
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,&statory Sensations
/u'ton and 0all,
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,&statory Sensations
• !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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,&statory Sensations
• !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