nerve impulses

Sensation

the process that occurs when special receptors in various sense organs are activated

sensory receptors

specialized forms of neurons, stimulated by different kinds of energy rather than by neurotransmitter

Transduction

turning outside stimuli into neural activity

Synesthesia

condition in which signals from the various sensory organs are processed differently, resulting in sense information being interpreted as more than one sensation

just noticable difference (jnd)

the smallest difference between two stimuli that is detectable 50 percent of the time

absolute threshold

the lowest level of stimulation that a person can consciously detect a stimulus 50 percent of the time it is present

subliminal stimuli

•stimuli that are below the level of conscious awareness

•Just strong enough to activate sensory receptors, but not strong enough for consciously awareness

•Limin: "threshold"; sublimin: "below the threshold"

subliminal perception

the process by which subliminal stimuli act upon the unconscious mind, possibly influencing behavior

Habituation

•The tendency of the brain to stop attending to constant, unchanging information
•Brain ignore unchanging information
•E.g., not hearing the aircon noise in the classroom

sensory adaptation

•The tendency of sensory receptor cells to become less responsive to a stimulus that is unchanging
•Receptors stop sending signal
•E.g., food taste fades after eating the same thing
•Eyes microsaccade (tiny movements) to prevent sensory adaptation

Light

•Light is a physical stimulus, composed of photons ("wave packets") and are associated with specific wavelengths

Brightness

•Determined by the amplitude of wave—how high or how low the wave actually is
•Higher the wave, the brighter the light will be

Color (hue)

•Determined by length of the wave
•Long wavelengths - red end of visible spectrum
Shorter wavelengths - blue end of visible spectrum

Saturation

•The purity of the color people see
•A highly saturated red contains only red wavelengths, whereas a less-saturated red would contain a mixture of wavelengths

Cornea

•clear membrane that covers the surface of the eye
•Protects the eye
•Focuses most of the light coming into the eye
•Fixed curvature

aqueous humor

•visual layer below cornea
•Clear, watery fluid that is continually replenished
•Supplies nourishment to the eye

pupil

hole through which light from the visual image enters the interior of the eye

iris

•round muscle (the colored part of the eye) in which the pupil is located
•Can change size of the pupil, letting more or less light into the eye
•Helps focus the image

lens

•another clear structure behind the iris, suspended by muscles
•Finishes the focusing process begun by the cornea
•Visual accommodation: the change in the thickness of the lens as the eye focuses on objects that are far away or close
•Loss of this ability due to hardening of the lens as we age results in a condition called presbyopia

Nearsightedness (myopia)

•Focal point fall short of the retina

farsightedness (hyperopia)

•Focus point is behind the retina

retina (contains 3 layers)

final stop for light in the eye

ganglion cells

its axons form the optic nerve

bipolar cells

interneuron

Photoreceptors

respond to various light waves and turns them into neural activity
•Rods
•Cones

Cones

•Responsible for color vision and sharpness of vision
•Work best in bright light
•Concentrated in the fovea

Rods

•Responsible for non-color sensitivity to low levels of light(process light but not colour)
•Work well in low levels of light
•Concentrated in the periphery

Blind spot

area in the retina where the axons of the three layers of retinal cells exit the eye to form the optic nerve; no receptors, insensitive to light

Color deficient vison (color blindness)

•Caused by defective cones in the retina

Monochromatic vision

•Have cones that are not working correctly as the result of genetic mutations.
•See no color, but different shades of grey ranging from black to white, rather like only seeing the world on an old black and white television set.

Dichromatic vision

•One cone does not work properly, rely on the combination of only two cones to see colors
•Protanopia
•Deuteranopia
•Tritanopia

Protanopia

red cones not working properly

Deuteranopia

green cones not working properly

Tritanopia

lack of blue cones

Wavelength

•interpreted as frequency or pitch

Amplitude

interpreted as volume (how soft or loud a sound is)

Purity

•interpreted as timbre (a richness in the tone of the sound)

Hertz (Hz)

cycles or waves per second, a measurement of frequency

Outer ear

•Pinna
•Auditory canal

Pinna

Visible part of the ear

auditory canal

short tunnel that runs from the pinna to the eardrum (tympanic membrane)

Middle ear

•eardrum
•anvil
•stirrup
•ossicles

eardrum

•Thin section of skin that tightly covers the opening into the middle part of the ear
•When sound waves hit the eardrum, it vibrates and causes three tiny bones, called ossicles

Ossicles vibrates

•Hammer
•Anvil
•Stirrup
•Ossicles amplify the vibration from the eardrum to inner ear via a membrane, called oval window

Inner ear

•cochlea
•organs of corti
•auditory nerve

Cochlea

•snail-shaped structure of the inner ear that is filled with fluid
•The fluid surrounds basilar membrane.

Organs of Corti

This is where the receptor cells for hearing, called hair cells, are located at.

Auditory nerve

•bundle of axons from the hair cells in the inner ear
•Receives neural message from the organ of Corti

Pitch

•how high or low a sound is
•Higher frequencies are perceived as higher pitches

Place theory

theory of pitch that states that different pitches are experienced by stimulation of hair cells in different locations on the organ of Corti

Frequency theory

•theory of pitch that states that pitch is related to the speed of vibrations in the basilar membrane
•Faster vibration = higher pitch

Volley principle

theory of pitch that states that group of auditory neurons take turns firing in a volley pattern

conduction hearing impairment

•Outer/middle ear problem, resulting in sound vibration unable to reach the inner ear
•Damaged eardrum
•Damage to bones of middle ear
•Hearing aids to restore hearing, by amplifying the sound

Nerve hearing impairment

•Damage in inner ear, or loss of hair cells
•Damage in auditory pathways and cortical areas of the brain
•Cochlear implant to restore hearing
•Microphone - detect the sound
•Speech processor - select and arrange the sound
•Implant - convert signals into electronic impulses
•Electrode array - collect electronic impulses in the cochlea