-
Module 5
- Sensation
- THREE DEFINITONS
- Adaptation:
- the decreasing response of the sense organs, the more they are exposed to a continuous level of stimulation
- Sensation versus perception:
- relatively meaningless bits of information that result when the brain processes electrical signals that come from the sense organs
- perceptions:
- meaningful sensory experiences that result after the brain combines hundreds of sensations
- THREE DEFINITONS (CONT.)
- eyes, ears, nose, skin, and tongue are complex, miniaturized, living sense organs that automatically gather information about your environment
- Transduction:
- process in which a sense organ changes, or transforms, physical energy into electrical signals that become neural impulses, which may be sent to the brain for processing
- 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
-
EYE: VISION (CONT.)
- Stimulus: Light Waves
- Invisible�too short
- wave lengths too short
- gamma rays, x-rays, ultraviolet rays
- Visible�just right
- Visible spectrum
- Particular segment of electromagnetic energy that we can see because these waves are the right length to stimulate receptors in the eye
- Invisible�too long
- wave lengths longer
- Radar, FM, TV, shortwave, AM
-
EYE: VISION (CONT.)
- EYE: VISION (CONT.)
- Structure and function
- Vision: 7 steps
- Image reversed
- Light waves
- Cornea
- Pupil
- Iris
- Lens
- Retina
-
EYE: VISION (CONT.)
- 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 (CONT.)
- 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 (CONT.)
- 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 (CONT.)
- 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
-
EYE: VISION (CONT.)
- EYE: VISION (CONT.)
- Retina:
- three layers of cells
- back layer contains two kinds of photoreceptors that begin the process of transduction
- change light waves into electrical signals
- rod located primarily in the periphery
- cone located primarily in the center of the retina called the fovea
-
EYE: VISION (CONT.)
- rods:
- photoreceptor that contain a single chemical, called rhodopsin
- activated by small amounts of light
- very light sensitive
- allow us to see in dim light
- see only black, white and shades of gray
-
EYE: VISION (CONT.)
- cones:
- photoreceptors that contain three chemicals called opsins
- activated in bright light
- allow us to see color
- cones are wired individually to neighboring cells
- allows us to see fine detail
-
EYE: VISION (CONT.)
- EYE: VISION (CONT.)
- Visual pathways: Eye to brain
- Optic nerve
- Primary visual cortex
- Visual association areas
- EYE: VISION (CONT.)
- EYE: VISION (CONT.)
- 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 (CONT.)
- Visual pathways: eye to brain
- Primary visual cortex
- the back of the occipital 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 (CONT.)
- Color Vision
- Trichromatic theory
- three different kinds of cones in the retina
- each cone contains one of the three different light-sensitive chemicals, called opsins
- each of the three opsins is most responsive to wavelengths that correspond to each of the three primary colors
- blue, green, red
- all colors can be mixed from these primary colors
-
EYE: VISION (CONT.)
- Opponent-Process Theory
- Afterimage
- visual sensation that continues after the original stimulus is removed
- ganglion cells in retina and cells in thalamus respond to two pairs of colors�red-green and blue-yellow
- when excited, respond to one color of the pair
- when inhibited, respond to complementary pair
-
EYE: VISION (CONT.)
- Color Blindness
- inability to distinguished two or more shades in the color spectrum
- Monochromatic:
- total color blindness
- black and white
- result of only rods and one kind of functioning cone
- Dichromatic:
- trouble distinguishing red from green
- two kinds of cones
- inherited genetic defect
- mostly in males
- See mostly shades of green
-
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 (CONT.)
- Loudness
- subjective experience of a sound�s intensity
- brain calculates loudness from specific physical energy (amplitude of sound waves)
- Pitch
- subjective experience of a sound being high or low
- brain calculates from specific physical stimuli
- speed or frequency of sound waves
- measured in cycles (how many sound waves in one second)
-
-
Measuring sound waves
- decibel: unit to measure loudness
- threshold for hearing:
- 0 decibels (no sound)
- 140 decibels (pain and permanent hearing loss)
-
EAR: AUDITION (CONT.)
EAR: AUDITION (CONT.)
-
Outer, middle, and inner ear
- Outer ear
- consists of three structures
- external ear
- auditory canal
- tympanic membrane
-
EAR: AUDITION (CONT.)
- 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 (CONT.)
- 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 (CONT.)
- 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
-
EAR: AUDITION (CONT.)
- EAR: AUDITION (CONT.)
- 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 (CONT.)
- Outer, middle, and inner ear
- Inner ear
- contains two structures sealed by bone
- cochlea: involved in hearing
- vestibular system: involved in balance
-
EAR: AUDITION (CONT.)
- 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 (CONT.)
- EAR: AUDITION (CONT.)
- 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 and 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
- Flavor
- combination of taste and smell
-
CHEMICAL SENSES (CONT.)
- CHEMICAL SENSES (CONT.)
- Smell, or olfaction
- Steps for olfaction
- Stimulus
- Olfactory cells
- Sensation and memories
- Functions of olfaction
-
CHEMICAL SENSES (CONT.)
- CHEMICAL SENSES (CONT.)
- Smell, or olfaction
- Stimulus
- we smell volatile substances
- volatile substances are released molecules in 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 patch of tissue in the uppermost part of the nasal passages.
- olfactory cells are covered in mucus
- which dissolve volatile molecules 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
-
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
-
TOUCH (CONT.)
- 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 first 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
-
PAIN (CONT.)
- 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
-
PAIN (CONT.)
- Dread
- connected to pain centers in brain
- not the act itself that people fear
- time waiting before event causes dread
-
Acupuncture
- trained practitioners insert thin needles into various points on the body�s surface and then manually twirls or electrically stimulates the needles
- after 10-20 minutes of stimulation, patients often report a reduction in various kinds of pain
|
|
