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

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

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

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

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

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

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)

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

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

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

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

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

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

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

p107 OLFACTORY BULB

CHEMICAL SENSES (CONT.) Smell, or olfaction Steps for olfaction Stimulus Olfactory cells Sensation and memories Functions of olfaction

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

CHEMICAL SENSES (CONT.) 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

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

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

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