Process of taking in stimuli from the
environment
Smallest amount of stimulus that can detected
at least half the time
Vision:1 candle flame,30 miles away on a dark
night
Hearing: tick of watch at 20 feet
Taste:1 teaspoon of sugar in 2 gallons of water
Smell:1 drop of perfume in a 3-room
apartment
Touch: wing of bee, on your cheek from 1 cm.
WOULD YOU NOTICE ONE CANDLE 30 MILES
AWAY ON A DARK NIGHT?
http://commons.wikimedia.org/wiki/File:Einzelne_Kerze.JPG
Signal Detection Theory:
No absolute thresholds,
because it is affected by
other factors like
attention, expectations,
motivations, emotions
Smallest difference between 2 stimuli that a
person can detect at least 50% of the time
Just-noticeable difference (jnd)
Weber’s Law: the difference threshold
increases in proportion to the original
stimuli
Vision: 8%
8 more candles to 100 candles to notice that
it’s brighter
Decreasing sensitivity to unchanging stimuli
-can focus attention on what’s important
-lose
delicious
smell at
the coffee
shop after
a while
http://commons.wikimedia.org/wiki/File:HK_Central_Mid-Level_Caine_Road_Starbucks_Coffee_Shop.JPG
Converting environmental stimuli into neural
impulses
-senses gather energy/chemicals from
environment
-must be converted into electrochemical
energy so that neurons can carry the
information to the brain to be processed
 Vision-light
waves
 Hearing-sound
waves
 Touch-pressure,
pain
temperature,
-light waves
Most
important
sense for
humans-rely
on it the most
http://commons.wikimedia.org/wiki/File:Cranach,_Lucas_d.J._-_Lucretia_-_Detail_face.JPG

Visual capture: tendency for vision to
dominate other senses
http://commons.wikimedia.org/wiki/File:Anato
my_and_physiology_of_animals_How_light_trave
ls_from_the_object_to_the_retina_of_the_eye.jpg
http://upload.wikimedia.org/wikipedia/commons/2/27/Retinal_anatomy.jpg
LIGHT IS
REFLECTED OFF OF
OBJECTS AND
ENTERS THE EYE
LIGHT IS FOCUSED
(ACCOMODATION)
ON THE RETINA BY
THE LENS
ACCORDING TO
DISTANCE
IT PASSES
THROUGH THE
PROTECTIVE
COVERING OF THE
CORNEA
RETINA RECEIVES
THE LIGHT UPSIDE
DOWN AND
INVERTED
IT ENTERS
THROUGH THE
PUPIL (BLACK
OPENING) WHICH IS
CONTROLLED BY
THE IRIS (COLORED
MUSCLE)
TRANSDUCTION
OCCURS IN THE
RETINA
Photoreceptors: cells sensitive to light
 3 Layers in retina:
1.-Rods: black/white/nighttime vision-in
peripheral vision
-Cones: color vision, best acuity,
concentrated in fovea (center of retina)
2. Bipolar cells: activate 3rd layer
3. Ganglion cells: connect to optic nerve
=Transduction (light to neural impulse)

Optic nerve
carries
messages into
the brain-where
leaves the brain
is blind spot
Optic chiasm:
half of each
optic nerve goes
to the opposite
hemisphere
Thalamus:
routes the visual
information to
the visual cortex
in the occipital
lobe
http://commons.wikimedia.org/wiki/F
ile:Constudeyepath.gif
ROY G BIV- VISIBLE SPECTRUM
-determined by light’s wavelength

http://commons.wikimedia.org/wik
i/File:Spectrummasthead.jpg
Theories:
1.Trichromatic theory: 3 types of
photoreceptors: red, green, blue
2. Opponent-process theory: colors come in
opposite pairs (afterimages, colorblindness)
-sound waves
Pitch=frequency of waves
Loudness=amplitude of waves
http://commons.wikimedia.org/wiki/File:HumanEar.jpg
Outer ear
collects and
amplifies
sounds
Oval window
vibrates the
cochlea
(transduction
happens here)
Tympanic
membrane
(eardrum)
vibrates with
the sound
waves
Hair cells inside
cochlea activate
the auditory
nerve which
carries messages
to the thalamus
Ossicles (3
bones in middle
ear) vibrate and
activate the Oval
Window
Thalamus sends
message to
auditory cortex
in the occipital
lobe
Conduction deafness: loss of hearing due to
inability to carry sound to inner ear
(punctured eardrum, ossicles)
-hearing aid
Sensorineural deafness: loss of hearing due to
damage in the cochlea or auditory nerve
-cochlear implant
-sensitive to tactile sensations: pressure,
warmth, cold, pain
-all other sensations are combination of these
4
-transduction
happens in skin
receptors located
all over the body
http://commons.wikimedia.org/wiki/File:LeftHand_2.png


Parietal lobe
Sensitivity of body part=larger section of
cortex
-is also inverted, top
controls the
bottom of the body
http://commons.wikimedia.org/wi
ki/File:Sensory_Homunculus.png
-associated with substance P
-natural pain killers are endorphins
-adaptive=causing damage, stop it
Gate-control theory: theory to explain pain
-must go through gate in spinal cord
-only most important pains go through
-scratch=no longer itch
TASTE (GUSTATION): tastebud receptors
-5 tastes: sweet, salty, sour, bitter, umami
-supertasters: most tastebuds
SMELL (OLFACTION): receptors in nostril
-only sense to not travel to thalamus 1st
-goes to limbic system=memory and emotion
Sensory interaction: work together to create
sensation
Kinesthesis: body position sense
-know where body parts are and movements
http://upload.wiki
media.org/wikipedi
a/commons/2/23/
Balance_beam_GM
M.jpg
Vestibular sense: sense of balance
-in inner ear-semicircular canals