a. unit iv lesson sensation

7/24/2019 A. Unit IV Lesson Sensation

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SENSATION and PERCEPTION

“All our knowledge has its origins in our perception”

Leonardo Da Vinci

I. Sensation It is the stimulus-detection process by which our sense organs respond to and translate

enironmental stimuli into nere impulses that are sent to the brain.

II. !erception

"aking #sense$ o% what our senses tell us- is the actie process o% organi&ing this stimulus

input and giing it meaning.

III. 'erminologies(

Stimulus- energy that produces a response in a sense organ.

!sychophysics- the study o% the relationship between the physical aspects o% stimuli and our

psychological e)perience o% them.

Absolute threshold- the smallest intensity o% a stimulus that must be present %or the stimulus to

be detected.

Some Appro)imate Absolute 'hresholds %or *umans

Sensory "odality Absolute 'hresholdVision +andle %lame seen at , miles on a clear dark night

*earing 'ick o% a watch under uiet conditions at / %eet

'aste 0 teaspoon o% sugar in / gallons o% water

Smell 0 drop o% per%ume di%%used into the entire olume o% a large

apartment

'ouch 1ing o% a %ly or bee %alling on a person$s cheek %rom a distance

o% 0 centimeter

234S'I56S to !56D47(

I. Stimulus Detection( 'he Absolute 'hreshold

*ow intense must a stimulus be be%ore we can detect its presence8

II. Signal Detection 'heory

Is concerned with the %actors that in%luence sensory 9udgments

III. Subliminal Stimuli( +an they A%%ect :ehaior8

Is one that is so weak or brie% that although it is receied by the senses; it cannot be perceied

consciously8

Sensory Adaptation <habituation= - the diminishing sensitiity to an unchanging stimulus

'he Di%%erence 'hresholds- is the smallest di%%erence between two stimuli that people can perceie

>? o% the time. <@erman physiologist 4rnst 1eber=



THE SENSORY SYSTEMS

'ransduction- is the process whereby the characteristics o% a stimulus are conerted into nere

impulses.

1. VISION

'he normal stimulus %or ision is electromagnetic energy or light waes; which are measured in

nanometers <nm=. 5ur isual system is sensitie only to waelengths e)tending %rom about nm

<red= down to about Bnm <blue-iolet=. Cou can remember the order o% the spectrum; %rom higher to

lower waelengths; with the name 75C @. :IV- red; orange; yellow; green; blue; indigo; and iolet.

1A. The Human Eye

Light waes enter the eye through the cornea; a transparent protective structure at the front of

the eye. :ehind the cornea is the pupil; an adjustable opening that can dilate or constrict to control

the amount of light that enters the eye . 'he pupil$s si&e is controlled by muscle in the colored iris that

surrounds the pupil. Low leels o% illumination cause the pupil to dilate; letting more light into the eye

to improe optical clarity bright lights make the pupil constrict.

:ehind the pupils is the lens; an elastic structure that becomes thinner to focus on distant

objects and thicker to focus on nearby objects. Eust a the lens o% a camera %ocuses an image on a

photosensitie materials <%ilm=; so the lens o% the eye %ocuses the isual image on the retina; a

multilayered light-sensitie tissue at the rear o% the %luid %illed eyeball.

1B. Some edical !onditions Affecting "ision

"yopia- i% you hae good ision %or nearby ob9ects but hae di%%iculty seeing %ar away ob9ects

*yperopia- people who hae e)cellent distant ision but hae di%%iculty seeing close-up ob9ects

clearly.

1!. #arts of the Human Eye

1$. #hotoreceptors% The &ods and !ones

'he retina; with its speciali&ed sensory neurons; is actually an e)tension o% your brain.

7ods- %unction best in dim light; primarily black-and-white brightness receptors. 'here are

about 0/ million rods. +ones- which are color receptors; %unction best in bright illumination. 'here are about F million

cones. Visual Acuity- the ability to see %ine detail.

1E. "isual Transduction% from light 'aves to nerve impulses

7ods and cones translate light waes into nere impulses through the action o% protein

molecule called photopigments.

1(. Activity%

(inding the Blind Spot

)shihara !olor Blindness Test * http://www.youtube.com/watch?v=sB28zwvY4Zg +



1,. Brightness "ision and dark Adaptation

Dark Adaptation- is the progressie improement in brightness sensitiity that occurs oer time

under conditions o% low illumination.

1H. !olor "ision

1e are blessed with a word rich in color. 'he ma9esty o% the glowing sunset; the rich blues and

greens o% tropical bay; the brilliant colors o% %all %oliage are all isual delights. *uman ision is %inelyattuned to color our di%%erence thresholds %or light waelengths are so small that we are able to

distinguish an estimated .> million hue ariations.

2. AUDITORY

'he stimuli %or our sense o% hearing are sound waes; a %orm o% mechanical energy. 1hat we call

sound is actually pressure waes in air; water; or some other conducting medium.

Greuency- is the number o% sound waes; or cycles; per second. 'he hert& <*&= is thetechnical measure o% cycles per second.

Amplitude- re%ers to the ertical si)e o% the sound waes- that is; the amount o% compression

and e)pansion o% the molecules in the conducting medium. 'he sound wae$s amplitude is the

primary determinant o% the sound$s perceied loudness. Di%%erences in amplitude are

e)pressed as decibels <d:=; a measure o% the physical pressures that occur at the eardrum.

-A. Auditory Transduction% (rom #ressure aves to /erve )mpulses

'he transduction system o% the ear is made up o% tiny bones; membranes; and liuid %illed

tubes designed to translate pressure waes into nere impulses. Sound waes trael into an auditory

canal leading to the eardrum; a membrane that vibrates in response to the sound 'aves. :eyond the

eardrum is the middle ear; a cavity housing three tiny bones. 'he ibrating actiity o% these bones- the

hammer <malleus=; anil <incus=; and stirrups <stapes= - ampli%ies the sound waes more than ,

times. 'he %irst bone; the hammer is attached %irmly to the eardrum; and the stirrup is attached to

another membrane; the oal window; 'hich forms the boundary bet'een the middle and inner ear .

'he inner ear contains the cochlea; a coiled0 snailshaped tube about 2.3 centimeters in length

that is filled 'ith fluid and contains the basilar membrane; a sheet o% tissue that runs its length.

7esting on the basilar membrane is the organ o% +orti; which contains thousands o% tiny hair cells that

are the actual sound receptors. 'he tip o%H the hair is attached to another membrane; the tectorial

membrane; 'hich overhangs the basilar membrane along the entire length of the cochlea .

-B. #arts of the Human Ear

-!. !oding of #itch and 4oudness

I. Greuency 'heory o% !itch !erception- nere impulses send to the brain match the %reuency o% the

sound wae.



II. !lace 'heory o% !itch !erception- suggesting that the speci%ic point in the cochlea where the %luid

wae peaks and most strongly bends the hair cells seres as a %reuency coding cue.

-$. Sound 4ocali5ation

Activity essage &elay 'ith a T'ist

-E. Hearing 4oss

I% you had to make the unwelcome choice o% being blind or dea%; which impairment would you

choose8 1hen asked this uestion; most o% our students say that they would rather be dea%. Cet

hearing loss can hae more deastating social conseuences than blindness does.

“:lindness cuts people o%% %ro m things. Dea%ness cuts people o%% %rom people.”

+onduction dea%ness- inoles problems with the mechanical system that transmit sound

waes to the cochlea. 6ere dea%ness- caused by damaged receptors within the inner ear or damage to the auditory

nere itsel%.

3. TASTE and SMELL: The Chemica Sen!e!

@ustation- the sense o% taste

5l%action- the sense o% smell

:oth are chemical senses their receptors are sensitie to chemical molecules rather than to

some other %orm o% energy. 'hese senses are so inter-twined that some scientists consider

them “common chemical sense”

2A. ,ustation% Sense of Taste

!eople who consider themseles gourmets are %reuently surprised to learn that their senses

respond to only %our ualities( sweet; sour; salty; and bitter.

'aste :uds- are chemical receptors concentrated along the tip; edges; and back sur%ace o% the

tongue. An additional taste sensation; called umami; increases the intensity o% other taste

ualities. "S@ is another substance that will enhance %laor. *umans hae about ; taste buds; each one consisting o% seeral receptor cells arranged

like the segments o% an orange.

2B. 6lfaction% The Sense of Smell

*umans are isually oriented creatures; but the sense o% smell is o% great importance %or many

species. 'he receptors %or smell are long cells that pro9ect through the lining o% the upper part o% the

nasal caity and into the mucous membrane.

*umans hae about B million ol%actory receptors; dogs about 0 billion.

5l%actory bulb- a %orebrain structure immediately aboe the nasal caity. 4ach odorous

chemical e)cites only a limited portion o% the ol%actory bulb; and odors are apparently coded in

terms o% the speci%ic area o% the ol%actory bulb that is e)cited. !heromone- chemical signals %ound in natural body scents; may a%%ect human behaior in

subtle ways.

". The S#IN and $ODY SENSES

'he skin and body senses include the senses o% touch; kinesthesis <muscle moement=; and

euilibrium. 'he last two are called body senses because they in%orm us o% the body$s position and

moement. 'hey tell us; %or e)ample; i% we are running or standing still; lying down or sitting up.

7A.The Tactile Senses

'ouch is important to us in many ways. Sensitiity to e)treme temperatures and to painenables us to escape e)ternal danger and alerts us to disorders within our body. 'actile sensations

are also a source o% many li%e$s pleasures; including se)ual orgasm.



*umans are sensitie to at least %our tactile sensations( pressure <touch=; pain; warmth; and

cold.

7B.The Body Senses

1e would be totally unable to coordinate our body moements were it not %or the sense o%

kinesthesis; which proides us with %eedback about our muscles$ and 9oints$ position and moement.

Vestibular sense- the sense o% body orientation; or euilibrium. 'he estibular receptors arelocated in the estibular apparatus in the inner ear.

SENSES AND PERCEPTION

Sensory "odality Stimulus 7eceptor +ells Absolute 'hreshold

VISI56 4lectromagnetic

1aes

7ods and +ones +andle %lame seen at , miles on

a clear dark night

*4A7I6@ Sound waes 5rgan o% +orti 'ick o% a watch under uiet

conditions at / %t.

'AS'4 Good 'aste :uds 0 tsp. o% sugar in / gallons o%water

S"4LL Scent 5l%actory cells 0 drop o% per%ume di%%used into a

three-room a

partment

'53+* !ain; pressure;

warmth; coldness

6ere 4ndings A bee$s wing %alling on your

cheek %rom 0 cm. aboe

0. VISION- isual sensation depends upon the interaction between the eye and the brain 4C4- globe-shaped and has a diameter o% appro)imately one inch.

a. Sclera- the tough opaue layer o% connectie tissue used to protect the inner

parts o% the eye.b. +horoids- contains some blood essels and absorbed imper%ectly %ocused

light raysc. 7etina- receiing area %or images; photosensitie is o% the eye; '734 organ

o% ision.

› 7ods- %unction chie%ly under low illumination

› Gunction in bright light.

Visual Acuity- sharpness o% ision which can be measured in terms o% the smallest

ob9ect that can be seen at a standard distance or the greatest distance at which a

standardi&ed ob9ect can be seen.

/. HEARIN%- the ital channel o% interaction with the enironment. 4A7- registers ibrations o% air particles

a. 5uter 4ar- composed o% the pinna; auditory canal and tympanic membraneb. "iddle 4ar- air %illed chamber that is connected to the pharyn) and composed

o% the , small bones or ossicles <hammer; anil and stirrup=c. Inner 4ar- %luid-%illed structure

Stimulus %or *earing

a. Greuency- re%ers to the number o% ibrations per second and determines the

pitch o% the sound.b. Intensity- re%ers to the amplitude o% the sound wae or the heights o% its

crests.c. 'imbre- re%ers to the oertones present in a sound in addition to the

%undamental tone.

3. TASTE & we en9oy the %ood we eat because o% this sense; otherwise; all kinds o% %ood

would simply taste %lat. @ustatory Senses- > basic taste senses

a. Sweetb. Sour

c. Saltyd. :itter e. 3mami



". SMELL' airborne molecules passing oer the e)posed %ibers trigger nere signals that

are sent to the brain "olecular %ingerprints' use distinctie patterns o% messages to recogni&e a

particular scent.

(. TOUCH' important sense that enhance man$s surial Gour Sensory Gunctions

a. 'hermal 4)perience- coldness; warmth). Gactual 4)perience- !ain; !ressurec. Jinesthetic sensation-d. Internal :odily "oement

a. unit iv lesson sensation

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