Motion sickness (sensory mismatch between information from the vestibular system)

symptoms: feelings of discomfort, nausea, and dizziness in a moving vehicle
head bouncing, but distant objects look fairly steady

Meniere's disease (malfunction of the semicircular canals of the vestibular system)

symptoms: dizziness, nausea, vomiting, spinning, and piercing buzzing sounds

Vertigo (malfunction of the semicircular canals of the vestibular system)

symptoms: dizziness and nausea

Taste

Chemical sense because the stimuli are various chemicals
Tongue
Surface of the tongue
Taste buds

Tongue
5 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 and 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

Flavor

Combination of taste and smell

Steps for olfaction

stimulus
olfactory cells
sensation and memories
functions of olfaction

Stimulus

we smell volatile substances
volatile substances are released molecules in the air at room temperature
examples: skunk spray, perfumes, warm brownies; not glass or steel

Olfactory cells

receptors for smell located in a one-inch-square patch of tissue in the uppermost part of the nasal passages
olfactory cells are covered in mucus that dissolves volatile molecules and stimulates the cells
the cells trigger nerve impulses that travel to the brain, which interprets the impulses as different smells

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
we can identify as many as 10,000 different odors
we stop smelling our deodorants or perfumes because of decreased responding (adaptation)

Functions of olfaction

one function: to intensify the taste of food
second function: to warn of potentially dangerous foods
third function: to elicit strong memories; emotional feelings

Touch

Includes pressure, temperature, and pain
Beneath the outer layer of skin are a half-dozen miniature sensors that are receptors for the sense of touch
Change mechanical pressure or temperature variations into nerve impulses that are sent to the brain for processing

Receptors in the skin

Skin
Hair receptors
Free nerve endings
Pacinian corpuscle

Skin

Outermost layer
Thin film of dead cells containing no receptors
Just below are first receptors, which look like groups of thread-like extensions
Middle and fatty layer
Variety of receptors with different shapes and functions
Some are hair receptors

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

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

Brain areas

Somatosensory cortex
Located in the parietal lobe
Transforms nerve impulses into sensations of touch, temperature, and 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

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

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

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 twirl or electrically stimulate the needles
After 10 to 20 minutes of stimulation, patients often report a reduction in various kinds of pain

Sensation

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

Adaptation

The decreasing response of the sense organs as they're 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

Stimulus: light waves

Invisible (too short)
gamma rays, x-rays, ultraviolet rays
Visible (just right)
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)
radar, FM, TV, shortwave, AM

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

transduction

process of Eyes perform two separate processes

Vision: seven steps

image reversed
light waves
cornea
pupil
iris
lens
retina

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

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

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

Retina

located at the very back of the eyeball; 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

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

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

Cones

Photoreceptors that contain three chemicals called opsins
Activated in bright light
Allow us to see color
Cones are wired individually to neighboring cells
Allow us to see fine detail

Visual pathways: eye to brain

Optic nerve
Primary visual cortex
Visual association areas

Optic 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

Primary visual cortex

back of the occipital lobes is where primary visual cortex transforms nerve impulses into simple visual sensations

Visual association areas

primary visual cortex sends simple visual sensations to neighboring association areas
damage to the visual association area = visual agnosia: difficulty in assembling simple visual sensations into more complex, meaningful images

Making colors from wavelengths

Sunlight is called white light because it contains all the light waves
White light passes through a prism; separates light waves that vary in length
Visual system transforms light waves of various lengths into millions of different colors
Shorter wavelengths of violet, blue, green
Longer wavelengths of yellow, orange, and red
An apple is seen as red because reflection of longer light waves that brain interprets as red

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

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

Color blindness

Inability to distinguish 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

inherited genetic defect; mostly in males
trouble distinguishing red from green
two kinds of cones
see mostly shades of green

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; amplitude

Frequency

number of sound waves occurring within a second

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 a second)

Measuring sound waves

Decibel: unit to measure loudness
Threshold for hearing
0 decibels (no sound)
140 decibels (pain and permanent hearing loss)

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

auditory canal

long tube that funnels sound waves down its length so that the waves strike the tympanic membrane (ear drum)

Outer ear
tympanic membrane

taut, thin structure commonly called the eardrum
sound waves strike the tympanic membrane and cause it to vibrate

Middle ear

bony cavity sealed at each end by membranes that 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)

Inner ear

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

Cochlea

Bony coiled exterior that resembles a snail's shell
Contains receptors for hearing
Function is transduction
Transforms vibrations into nerve impulses 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 (meaningful melodies, songs, words, or sentences)

Direction of sound

determined by brain; calculates slight difference in time it takes sound waves to reach the two ears

Calculating pitch

frequency theory
applies only to low-pitched sounds
rate ate that nerve impulses reach the brain determines how low a sound's pitch is
place theory
brain determines medium-to-higher-pitched sounds from the place on the basilar membrane where maximum vibration occurs

Calculating loudness

brain calculates loudness primarily from the frequency or rate of how fast or how slow nerve impulses arrive from the auditory nerve

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
Includes sensing the position of the head, keeping the head upright, and maintaining balance