26Introduction Sensory nervous system is responsible for the processing of sensory 27information or stimuli received from the e(ternal and internal environment of an 28organism. Sensory receptors) neural path*ays and the brain are important in sensory 29perception. +n line *ith this) the e(periment aims to evaluate the human sensory system 30specifically somatosensory system) auditory system) and visual system through various 31tests. 32!ethods The test sub,ects under*ent various activities for the evaluation of their 33sensory system. Tactile locali!ation) touch receptor adaptation and temperature 34receptors *ere considered in the assessment of their somatosensory perception) 35auditory acuity -via *atch tic test/ and auditory adaptation for hearing perception) and 36binocular vision and space perception) and visual acuity for their visual perception. 37"esults #or tactile locali!ation) the test sub,ects did not accurately locate the e(act 38spot *here the stimulus *as applied. #or touch receptors adaptation) it sho*ed a 39positive correlation bet*een the magnitude of the stimulus and the duration of initial 40perception. #or temperature receptors) it *as observed that at ice *ater) there *as no 41sensation perceived *hile at 01 C) there *as a *arm sensation. #or auditory acuity) it °
42*as observed that the distance *here the stimulus could be perceived *as longer *hen 43the stimulus *as gradually decreasing as compared to *hen it *as gradually 44increasing. #or auditory adaptation) it *as noted that there *as little to none stimulus 45perceived *hen the rubber tubing *as firmly pressed to the ears. #or binocular vision 46and space perception) and visual acuity) there *as a variation in the perception of the 47stimuli. 48#onclusion The human sensory system perceives stimuli at different rates in terms of 49locali!ation) perception and duration) *hich reflects on the types of receptors that are in 50the region of e(posure. 512ey*ords3 hearing, perception, sensory system, somatic senses, vision 52 53
54Introduction 55
Sensory nervous system is a part of the nervous system that processes sensory
56information received from the e(ternal and internal environment. +t consists of sensory 57receptors) neural path*ays and parts of the brain that are responsible for sensory 58perception. Sensory receptors receives stimulus from the e(ternal and internal 59environment. Chemoreceptors -detect the presence and changes in ions and molecules 60 4 smell) taste/) mechanoreceptors -detect changes and fluctuations in pressure) position 61and movement 4 hearing) touch) balance/) photoreceptors or electromagnetic receptors 62-detect light) radiation and magnetic fields 4 sight/) thermoreceptors -detect hot and cold 63temperatures/) and nociceptors -detect pressure) chemicals and severe heat that cause 64damage5pain/ are the different types of receptors present in organisms. Sensory 65neurons transmit information from the sensory receptors to*ards the Central 6ervous 66System -C6S/ *here the processing of the information happens. The C6S *ill then 67transmit impulses in response to the information it received to effectors -muscle) glands) 68organs/ via motor neurons. The sensory nervous system assists in the survival of the 69organism against e(ternal threats and also regulates its internal environment.
The
70ob,ective of this e(periment is to evaluate the performance of the human sensory 71system specifically the somatosensory system) auditory system and visual system 72through various tests. 73 74!aterials and !ethods 75Somatic Senses 76
Tactile Localization. 7ith the sub,ect8s eyes closed) their sin *as touched *ith a
77pointed pencil. The sub,ect *as ased to touch the same spot using the same ob,ect. 78The locali!ation difference) in millimetres) *as measured. The procedure *as repeated 79and the improvement in the locali!ation) if any) *as noted. The procedure *as 80performed t*ice on other parts of the body and the results *ere tabulated. 81
Touch Receptors Adaptation. 7ith the sub,ect8s eyes closed) a small coin *as
82placed on the inside of their forearm. The time of initial perception *as measured. T*o
83more coins *ere added *hen the sensation *as no longer felt by the sub,ect. The 84sensation of the e(tra coins *as timed.
Temperature Receptors. The sub,ect8s left hand *as placed in a &%%% ml beaer
85
86filled *ith ice *ater and their right hand simultaneously in a &%%% ml beaer of *ater at 87019C for t*o minutes. The sensation felt by each hand *as recorded. 88Hearing
Watch Tick Test for Auditory Acuity. The sub,ect *as made to close their eyes
89
90and their ear *as plugged *ith cotton. : *atch *as held against the auditory canal of 91the unplugged ear and *as slo*ly moved a*ay until the sub,ect can no longer hear it) 92and the distance *as measured. The *atch *as moved closer until the sub,ect can hear 93it again. The distance *as measured and the difference *as noted) if any. The 94procedure *as repeated *ith the other ear. 95
Auditory Adaptation. : stethoscope *as placed on the sub,ect8s ears then a
96tuning for *as vibrated at the bell of the stethoscope. The tuning for *as removed 97and the sub,ect *as allo*ed to rest for t*o minutes *ithout removing the stethoscope. 98The procedure *as repeated but *hile pressing firmly on the rubber tube leading to one 99ear. The for *as moved a*ay so that the sound *as barely heard on the free ear. :t 100this point) the pressure to the other ear *as released. The sensation felt by the sub,ect 101*as recorded. 102ision 103
!inocular ision and Space "erception. The sub,ect *as ased to focus on a
104coin held in front of their nose. They *ere ased to close one eye) open it) and then 105close the other. The difference in the position of the coin *as noted. 106
isual Acuity. The sub,ect *as ased to stand $% feet from a Snellen "ye Chart.
107They *ere ased to cover one eye and try to read the ;
th
line. +f the sub,ect *as able to
108read the ; th line) they *ere ased to try reading the < th line. The procedure *as repeated 109using the other eye. 110
111"esults 112
$able % Tactile =ocali!ation Part of the Body
&ocali'ation (ifference )mm*
#orearm -left/
&$
%$>and -left/
$
&
#oot -left/
&?
<
:rm -left/
?<
?'
=eg -right/
$;
$&
113
$able + Touch Receptors :daptation No of #oins @roup A &
@roup <
$ime of Perception )s* 0$ s
$
;& s
? &
<$ s <.&A s
$
$%.10 s
?
$A.%' s
114
$able 3 Temperature Receptors Sensation in ice ,ater
Sensation in 4-.# ,ater
@roup A
6umb) no feeling
Rela(ing) *armer than normal temperature
@roup <
6umb after &$% s
7arm sensation
115
$able 4 7atch tic test (istance from ear to point ,here sub/ect cannot hear
@roup A
@roup <
R $.1
(istance ,here sub/ect can hear again &.1
&.%
=
$.1
0.%
R &&' mm
1? mm
'? mm
=
01 mm
1& mm
'.1
<' mm
(ifferenc e
116
$able - :uditory :daptation Sensation
Sensation
)normal*
)rubber tubing pressed*
@roup A
Both ears heard the sound of the tuning for
6o sound heard on the ear *here the tube *as pressed
@roup <
=oud vibrating sensation
Short faint sensation
117
$able 0 Binocular ision and Sense erception and isual :cuity
118
Binocular 1ision and Sense Perception
1isual Acuity
@roup A
The coin loos farther *hen the right eye is used for focusing.
Both eyes *ere not able to read line ;.
@roup <
7hen the left eye is closed) the coin appears to be at the left peripheral vie*. 7hen the right eye is closed) the coin appears to be at the center.
=ine ; *as clearly read *ith both eyes. nly one number *as clearly able to read line < *ith one eye.
119(iscussion 120
>uman sensory systems composes parts of the nervous system responsible for
121processing sensory information as *ell as the visual) auditory) gustatory) olfactory and 122somatic system. The sensory organs are equipped to respond to a particular stimulus 123from the environment -Saladin) $%%;/. The sensory system is made up of different 124receptors each corresponding to the stimulus received by the body) these are 125thermoreceptors) photoreceptors) mechanoreceptors and chemoreceptors *hich are 126unevenly distributed throughout the body 127
The sense of touch is the first sense to develop and functions even after other
128senses start to *eaen -Saladin) $%%; ). Stimulus is sent from the receptors and 129processed in the somatosensory area in the parietal lobe of the cerebral corte( -RoblesE 130dela Torre) $%%'/ to be felt on that area of the body *here stimulus *as received. 131
The disparity bet*een the temperature sensation in the left and right hand
132describes the *or of thermoreceptors *hich are spread throughout the body. :fter 133prolonged sub,ection to cold and hot *ater) the nerve endings have been less sensitive 134to the stimulus triggering a decrease in the electrical signal transmitted to the 135somatosensory part of the brain as seen in the numbing effect after &$% secondsF this 136phenomenon is called sensory adaptation. Sensory adaptation occurs *hen the sensory 137receptors change their sensitivity in relation to the stimulus. :ll human senses) *ith the 138e(ception of the sense of pain) e(perience sensory adaptation. 139
The eye is composed of structures *hose main focus is to optimi!e the light rays
140on its retina. ision begins as the light enters through the first refractive inde( of the 141eye) the cornea. This transparent outer covering bends the light as it passes through the 142pupil. The iris surrounding the pupil open or closes corresponding to the amount of light 143passing through. The light moves on to the lens to be bent even further and focused on 144the retina. The photoreceptors are found in the retina are distinguished by their distinct 145shapes and its location *ithin an area called macula determines its function. Cones that 146*or *ell in daylight are found *ithin and is concentrated at the center of the retina to 147provide central vision and detect finer details *hile rods that *or in dim light to night is 148located around the rim of the retina to provide peripheral vision. These tiny lightEsensing
149nerve cells convert light into energy impulses to be sent to the brain through the optic 150nerve to produce an image -::) $%&&/. 151
There are numerous *ays to gauge the visual ability of an individual) among
152these are the binocular vision and sense perception and visual acuity. isual acuity 153refers to the clarity or sharpness of a vision. +t solely describes the distance at *hich an 154image seen is still clear so other visual sills lie peripheral vision) depth perception) 155focusing ability and color vision dictate the overall visual ability. The Snellen eye chart is 156commonly used to determine visual acuity. +t features && ro*s of capital letters *ith the 157top ro* containing one letter. The si!es of the letters gradually becomes small as the 158line progresses do*n. 6umbers are observed at the sides of the chart indicating the 159distance. The term $%5$% vision therefore is used to e(press normal visual acuity at $% 160feet. To further visuali!e an ob,ect) the human eye has to see in three dimension -length 161*idth and height/) this is no*n as depth perception. "ach eye produces a slight 162difference in the distance of an ob,ect *hen used separate from the other as *as 163observed. +n both groups) the right eye seems to sho* the almost accurate location of 164the coin *hich may mean that it is the dominant eye. The binocularity of human eyes 165sho*s both *oring in sync to produce the correct distance of an ob,ect ->ess G 166Thompson) $%&1F =evi) 2nill G Bevalier) $%&1/. 167
The auditory system is composed of the outer) middle) and inner ear. +nside the
168inner ear) there are numerous hair cells that respond to sound. >uman hair cells have 169various speciali!ations that correspond to *hat they are responding to) such as hairs 170that respond to sound) rotation) and gravity -@ray) $%&&/. Sound energy is focused on 171the basilar membrane. :s the membrane vibrates) the hair cells are bent to initiate 172action potentials that travel along the auditory nerve to the brain centers for processing 173of sound to information. 174
The 7atch Tic Test is a simple and useful test for acuity. +t relies on the ability of
175a person to pic up highEfrequency tics from a *atch being held close to their ear and 176then gradually moved a*ay. The distance at *hich the sub,ect can no longer hear the 177ticing is compared *ith the distance at the other ear. : useful comparison can then be
178made that *ill determine the auditory acuity of both ears. >ighEtone deafness is also 179measured by this test -Reeves and S*enson) $%%%/. 180
:s *ith somatosensory e(periments) sensory adaptation is also observed in the
181auditory system *as tested) aptly called auditory adaptation. This test) lie the *atch 182tic test) is simple and maes use of only a stethoscope and a tuning for. :s loud 183sound reaches the ear) the muscle attached to one of the bones in the inner ear 184contracts) causing the reduction of transmission of sound vibrations to the inner ear) 185*here the vibrations are detected -Sincero) $%&?/. :uditory adaptation) ho*ever) does 186not *or *ith instantaneous loud sounds such as gun shots or e(plosions. 187 188#onclusion 189
>uman sensory system receives stimuli upon e(posure and then directs it to the
190nerve center. The e(tensions of the sensory capabilities of the said system are 191observed through the physical tests that are conducted on somatic) auditory and visual 192perception. +n terms of cutaneous receptors) each receptor is assigned a specific region 193in the sin to receive stimuli. +n these terms) the nerves could ma(imi!e the area of 194*here they can perceive tactile stimuli. n the other hand) if more than one stimulus is 195applied to the same region of the receptor) only one of them *ill be recogni!ed by the 196central nervous system. +n e(tension) certain stimuli) even if applied in prolonged 197periods) can ad,ust the rate of action potential generated by the receptor and therefore) 198*ould *ane upon chronic stimulation. This case applies to the *ide array of sensory 199perception of the human body) specifically in tactile) auditory and visual senses. Sounds 200*here the auditory system is accustomed and are e(uded in continuous frequencies 201*ould allo* the auditory senses to adapt and lose sensitivity to the stimuli. :lso) visual 202perception may have different depths depending on *hich eye interprets the image. 203ro(imity and positioning are essential in discerning the efficiency of the sense of 204vision. Therefore) the human sensory system perceives stimuli at different rates in terms 205of locali!ation) perception and duration) *hich reflects on the types of receptors that are 206in the region of e(posure. 207
208Ac2no,ledgements 209
This study *as supported by the College of Science Department of Biology and
210housed at Room ?$;: Third #loor ain Building. 7e are grateful of Sir Castillo and s. 211Rimando for their guidance and support. 212
217>ess) R. G Thompson) B.-$%&1/. Am%lyopia and the %inocular approach to its therapy. 218 Retrieved from 219http355***.sciencedirect.com5science5article5pii5S%%0$'<;<&1%%%1$; 221=evi) D.) 2nill) D.) G Bavelier) D. -$%&1/. Stereopsis and am%lyopia$ A mini&revie#. 222 223
Retrieved from http355***.sciencedirect.com5science5article5pii5S%%0$'<;<&1%%%%;1
224Reeves) :.@.) G S*enson) S. -$%%%/ 'isorders on the nervous system$ A "rimer.
Retrieved from https355***.dartmouth.edu5Hdons5partI&5chapterI'.html
225
226RoblesEdela Torre) @. -$%%'/. The (mportance of the Sense of Touch in irtual and Real
