Introduction to Psychology, 7th Edition, Rod Plotnik Module 5: Sensation Module 5 Sensation

Introduction to Psychology, 7th Edition, Rod PlotnikModule 5: Sensation

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


p95 EYE


EYE: VISION

• Structure and function– Vision: 7 steps

• Image reversed• Light waves• Cornea• Pupil• Iris• Lens• Retina


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


• 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

EYE: VISION


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


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


p96 RETINA


EYE: VISION

• Visual pathways: Eye to brain– Optic nerve– Primary visual cortex– Visual association areas


p97 VISUAL SYSTEM


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


• 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

EYE: VISION


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


EAR: AUDITION

• Measuring sound waves– decibel: unit to measure loudness– threshold for hearing:

• 0 decibels (no sound)• 140 decibels (pain and permanent hearing loss


p101 DECIBEL CHART


EAR: AUDITION

• Outer, middle, and inner ear– Outer ear

• consists of three structures• external ear• auditory canal• tympanic membrane



• 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

EAR: AUDITION


EAR: AUDITION


• auditory canal– long tube that funnels sound waves down its

length so that the waves strike the tympanic membrane (ear drum)


EAR: AUDITION


• tympanic membrane– taut, thin structure commonly called the

eardrum– Sound waves strike the tympanic

membrane and cause it to vibrate


p102 EAR DIAGRAM


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)


EAR: AUDITION

• Outer, middle, and inner ear– Inner ear

• contains two structures sealed by bone– cochlea: involved in hearing– vestibular system: involved in balance


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


• 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

EAR: AUDITION


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


CHEMICAL SENSES

• Taste– chemical sense because the stimuli are various

chemicals– tongue– surface of the tongue– taste buds


CHEMICAL SENSES (CONT.)

• Tongue– Five basic tastes

• sweet• salty• sour• bitter• umami: meaty-cheesy taste



• 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



• 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



• 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


p107 OLFACTORY BULB



• Smell, or olfaction– Steps for olfaction

• Stimulus• Olfactory cells• Sensation and memories• Functions of olfaction



• 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



• Smell, or olfaction– Olfactory cells

• receptors for smell are located in a I-inch-square 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



• 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



• 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


TOUCH

• Touch– includes pressure, temperature, and pain


p108 SKIN


TOUCH (CONT.)

• Receptors in the skin– skin– hair receptors– free nerve endings– Pacinian corpuscle


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


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


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


TOUCH (CONT.)

• Brain areas– somatosensory cortex– located in the parietal lobe– transforms nerve impulses into sensations of

touch temperature, and pain


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


p112 BRAIN PAIN


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


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

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Introduction to Psychology, 7th Edition, Rod Plotnik Module 5: Sensation Module 5 Sensation