Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
Module 5
Sensation
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EYE: VISION
• Structure and function
– eyes perform two separate processes
– first: gather and focus light into precise area in the
back of eye
– second: area absorbs and transforms light waves
into electrical impulses
– process called transduction
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
p95 EYE
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EYE: VISION
• Structure and function
– Vision: 7 steps
• Image reversed
• Light waves
• Cornea
• Pupil
• Iris
• Lens
• Retina
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EYE: VISION
• Structure and function
– Image reversed
• In the back of the eye, objects appear upside
down.
• somehow the brain turns the objects right side
up
– Light waves
• light waves are changed from broad beams to
narrow, focused ones
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EYE: VISION
• Structure and function
– Cornea
• rounded, transparent covering over the front of
your eye
– Pupil
• round opening at the front of the eye that allows
light waves to pass into the eye’s interior
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EYE: VISION
• Structure and function
– Iris
• circular muscle that surrounds the pupil and
controls the amount of light entering the eye
– Lens
• transparent, oval structure whose curved
surface bends and focuses light waves into an
even narrower beam
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EYE: VISION
• Structure and function
– Retina
• located at the very back of the eyeball, is a thin
film that contains cells that are extremely
sensitive to light
• light sensitive cells, called photoreceptors,
begin the process of transduction by absorbing
light waves
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
p96 RETINA
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EYE: VISION
• Visual pathways: Eye to brain
– Optic nerve
– Primary visual cortex
– Visual association areas
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
p97 VISUAL SYSTEM
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EYE: VISION
• Visual pathways: eye to brain
– Optic nerve
• nerve impulses flow through the optic nerve as
it exits from the back of the eye
• the exit point is the “blind spot”
• the optic nerves partially cross and pass
through the thalamus
• the thalamus relays impulses to the back of the
occipital lobe in the right and left hemisphere
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EYE: VISION
• Visual pathways: eye to brain
– Primary visual cortex
• the backs of the occipitals lobes is where
primary visual cortex transforms nerve
impulses into simple visual sensations
– Visual association areas
• the primary visual cortex sends simple visual
sensations to neighboring association areas
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EAR: AUDITION
• Stimulus:
– Sound waves
• stimuli for hearing (audition)
• ripples of different sizes
• Sound waves travel through space with varying
heights and frequency.
– Height
• distance from the bottom to the top of a sound
wave
• called amplitude
– Frequency
• number of sound waves occurring within one
second
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EAR: AUDITION
• Measuring sound waves
– decibel: unit to measure loudness
– threshold for hearing:
• 0 decibels (no sound)
• 140 decibels (pain and permanent hearing loss
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
p101 DECIBEL CHART
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EAR: AUDITION
• Outer, middle, and inner ear
– Outer ear
• consists of three structures
• external ear
• auditory canal
• tympanic membrane
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EAR: AUDITION
• Outer, middle, and inner ear
– Outer ear
• external ear
– oval shaped structure that protrudes from
the side of the head
• function
– pick up sound waves and then send them
down the auditory canal
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EAR: AUDITION
• Outer, middle, and inner ear
– Outer ear
• auditory canal
– long tube that funnels sound waves down its
length so that the waves strike the tympanic
membrane (ear drum)
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EAR: AUDITION
• Outer, middle, and inner ear
– Outer ear
• tympanic membrane
– taut, thin structure commonly called the
eardrum
– Sound waves strike the tympanic
membrane and cause it to vibrate
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
p102 EAR DIAGRAM
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EAR: AUDITION
• Outer, middle, and inner ear
– Middle ear
• bony cavity sealed at each end by membranes.
• the membranes are connected by three tiny
bones called ossicles
• hammer, anvil and stirrup
– hammer is attached to the back of the
tympanic membrane
– anvil receives vibrations from the hammer
– stirrup makes the connection to the oval
window (end membrane)
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EAR: AUDITION
• Outer, middle, and inner ear
– Inner ear
• contains two structures sealed by bone
– cochlea: involved in hearing
– vestibular system: involved in balance
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EAR: AUDITION
• Cochlea
– bony coiled exterior that resembles a snail’s shell
– contains receptors for hearing
– function is transduction
– transforms vibrations into nerve impulses that are
sent to the brain for processing into auditory
information
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
EAR: AUDITION
• Auditory brain areas
– sensations and perceptions
– two step process occurs after the nerve impulses
reach the brain
– primary auditory cortex
– top edge of temporal lobe
– transforms nerve impulses into basic auditory
sensations
– auditory association area
– combines meaningless auditory sensations into
perceptions, which are meaningful melodies,
songs, words, or sentences
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
VESTIBULAR SYSTEM: BALANCE
• Position and balance
– vestibular system is located above the cochlea in
the inner ear
– includes semicircular canals
– bony arches set at different angles
– each semicircular canal is filled with fluid that
moves in response to movements of your head
– canals have hair cells that respond to the fluid
movement
– function of vestibular system
– include sensing the position of the head, keeping
the head upright, and maintaining balance
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
CHEMICAL SENSES
• Taste
– chemical sense because the stimuli are various
chemicals
– tongue
– surface of the tongue
– taste buds
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
CHEMICAL SENSES (CONT.)
• Tongue
– Five basic tastes
• sweet
• salty
• sour
• bitter
• umami: meaty-cheesy taste
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
CHEMICAL SENSES (CONT.)
• Surface of the tongue
– chemicals, which are the stimuli for taste, break
down into molecules
– molecules mix with saliva an run into narrow
trenches on the surface of the tongue
– molecules then stimulate the taste buds
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
CHEMICAL SENSES (CONT.)
• Taste buds
– shaped like miniature onions
– receptors for taste
– chemicals dissolved in saliva activate taste buds
– produce nerve impulses that reach areas of the
brain’s parietal lobe
– brain transforms impulses into sensations of taste
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
CHEMICAL SENSES (CONT.)
• Smell, or olfaction
– Olfaction
• called a chemical sense because its stimuli are
various chemicals that are carried by the air
• Function of olfaction
– receptors, through transduction, transform
chemical reactions into nerve impulses
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
p107 OLFACTORY BULB
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
CHEMICAL SENSES (CONT.)
• Smell, or olfaction
– Steps for olfaction
• Stimulus
• Olfactory cells
• Sensation and memories
• Functions of olfaction
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
CHEMICAL SENSES (CONT.)
• Smell, or olfaction
– Stimulus
• we smell volatile substances
• volatile substances are released molecules in
the the air at room temperature
• example:
– skunk spray, perfumes, warm brownies; not
glass or steel
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
CHEMICAL SENSES (CONT.)
• Smell, or olfaction
– Olfactory cells
• receptors for smell are located in a I-inchsquare patches of tissue in the uppermost part
of the nasal passages.
• olfactory cells are covered in mucus
• which volatile molecules dissolve and stimulate
the cells
• the cells trigger nerve impulses that travel to
the brain
• which interprets the impulses as different
smells
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
CHEMICAL SENSES (CONT.)
• Smell, or olfaction
– Sensations and memories
• nerve impulses travel to the olfactory bulb
• impulses are relayed to the primary olfactory
cortex
• cortex transforms nerve impulses into olfactory
sensations
• Can identify as many as 10,000 different odors
• we stop smelling our deodorants or perfumes
because of decreased responding
• called adaptation
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
CHEMICAL SENSES (CONT.)
• Smell, or olfaction
– Functions of olfaction
• one function: to intensify the taste of food
• second function: to warn of potentially
dangerous foods
• third function: elicit strong memories; emotional
feelings
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
TOUCH
• Touch
– includes pressure, temperature, and pain
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
p108 SKIN
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
TOUCH (CONT.)
• Receptors in the skin
– skin
– hair receptors
– free nerve endings
– Pacinian corpuscle
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
TOUCH (CONT.)
• Skin
– outermost layer
– thin film of dead cells containing no receptors
– just below, are fist receptors which look like
groups of threadlike extensions
– middle and fatty layer
– variety of receptors with different shapes and
functions
– some are hair receptors
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
TOUCH (CONT.)
• Hair receptors
– free nerve endings wrapped around the base of
each hair follicle
– hair follicles fire with a burst of activity when first
bent
– If hair remains bent for a period of time, the
receptors will cease firing.
– sensory adaptation
– example: wearing a watch
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
TOUCH (CONT.)
• Free nerve endings
– near bottom of the outer layer of skin
– have nothing protecting or surrounding them
• Pacinian corpuscle
– in fatty layer of skin
– largest touch sensor
– highly sensitive to touch
– responds to vibration and adapts very quickly
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
TOUCH (CONT.)
• Brain areas
– somatosensory cortex
– located in the parietal lobe
– transforms nerve impulses into sensations of
touch temperature, and pain
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
PAIN
• What causes pain?
– pain: unpleasant sensory and emotional
experience that may result from tissue damage,
one’s thoughts or beliefs, or environmental
stressors
– pain results from many different stimuli
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
p112 BRAIN PAIN
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
PAIN (CONT.)
• How does the mind stop pain?
– gate control theory of pain
– nonpainful nerve impulses compete with pain
impulses in trying to reach the brain
– creates a bottleneck or neutral gate
– shifting attention or rubbing an injured area
decreases the passage of painful impulses
– result: pain is dulled
Introduction to Psychology, 7th Edition, Rod Plotnik
Module 5: Sensation
PAIN (CONT.)
• Endorphins
– chemicals produced by the brain and secreted in
response to injury or severe physical or
psychological stress
– pain reducing properties of endorphins are similar
to those of morphine
– brain produces endorphins in situations that evoke
great fear, anxiety, stress or bodily injury as well
as intense aerobic activity