PSY100 Topic 3

Sensation

result of energy (light) stimulating a sense organ (eye).

Perception

the process of creating meaningful patterns (a word) from raw sensory information.

Vision

considered by many to be our most important sense.

Cornea

clear protective layer on the front of eye.

Iris

colored part of eye, opens and closes to let in more or less light.

Pupil

opening created by iris through which light passes.

Lens

changes shape to focus on objects at different distances.

Aqueous humor

watery fluid in front of the lens (anterior cavity) nourishes the lens and cornea.

Vitreous humor

jelly-like fluid behind the lens (posterior cavity). Literally holds the retina in place and gives structure to the eyeball.

Accommodation

tiny muscles change the shape of the lens to focus on far or near objects.

Presbyopia

“old sightedness” or “short arm syndrome.” Ciliary bodies lose their elasticity and can no longer change the shape of the lens to bring near objects into focus.

Myopia

nearsightedness, image focuses in front of the retina rather than on it, eyeball is elongated. Corrected by glasses, contacts or radial keratotomy (Lasix).

Hyperopia

“farsightedness,” image focuses behind the retina, produces a fuzzy image. Corrected by lenses.

Astigmatism

refraction error – fuzzy image, irregular curvature of the cornea or lens, requires special lenses to correct (Toric lenses) or contacts.

Retina

inner layer on back of eye that contains “light-sensitive” rods and cones

Optic Nerve

bundle of axons running from retina to visual (occipital) cortex.

Blind Spot (Optic disc)

spot on the retina where optic nerve exits eye, there are no receptors (rods or cones) there.

Fovea

center of the retina where “acuity” (ability to see fine detail) is greatest.

Receptor cells

rods and cones, fire in response to light.

Bipolar cells

carry signals from receptors to ganglion cells.

Ganglion cells

axons of ganglion cells form the optic nerve.

Rods

located mainly in periphery; responsible for night vision; detail not detected; see black, white, and gray; several rods share 1 bipolar and 1 ganglion cell.

Cones

located mainly in fovea; work best in bright light; enable us to see fine detail; responsible for color vision; each cone has its own bipolar and ganglion cell.

Dark adaptation

increased sensitivity of rods and cones in darkness.

Hue

the actual color (red, green, etc.); determined by wavelength of light.

Saturation

how pure and vivid the color is.

Brightness

intensity of the light.

Complementary Colors

pair of colors that when mixed cancel out to produce “gray” (Red-Green, Blue-Yellow).

Trichromats

people with normal color vision.

Dichromats

can’t distinguish either red from green or yellow from blue.

Monochromats

people who are totally colorblind, more severe.

Pitch

determined by frequency (cycles per second).

Loudness

determined by amplitude (height) of the sound wave.

Timbre

determined by complexity and shape of the sound wave, gives unique quality.

Pinna

directs sound waves into the auditory canal.

Auditory Canal

conducts sound to the eardrum.

Eardrum

thin membrane that vibrates in response to sound, transfers energy to bones.

Hammer, Anvil, Stirrup

three tiny bones that amplify sound and transfer to inner ear.

Cochlea

snail shaped fluid-filled structure.

Oval window

thin membrane, transfers vibrations from stirrup to cochlea.

Basilar membrane

runs the length of the cochlea.

Organ of Corti

rests on basilar membrane, contains receptor cells.

Round window

absorbs energy and equalizes pressure in cochlea.

Hair cells

receptor cells with fibers that bend with fluid waves, causing cells to fire.

Auditory nerve

axons from receptor cells that carry sound to brain.

Vestibular sense

information about balance and body position.

Semi-circular canals

sense body rotation.

Utricle

senses horizontal movement.

Saccule

senses vertical movement/gravity.

Taste buds

chemical receptors that generate nervous impulses resulting in the sense of taste (about 10,000 on papillae).

Olfactory receptors

chemical receptors responsible for the sense of smell located in the upper nasal cavity.

Encapsulated nerve endings

dermis; touch and pressure.

Free nerve endings

dermis, mucosa, internal organs; pain or crude touch.

Meissner’s corpuscles

fingertips and lips; fine touch and vibration.

Ruffini’s corpuscles

fingers; touch and pressure.

Pacinian corpuscles

subcutaneous; deep pressure and vibration.

Krause’ end bulbs

skin and SQ; touch and maybe cold.

Muscle spindles

skeletal muscle; proprioception (sense of position/movement).

Size constancy

object remains same size despite retinal changes.

Shape constancy

object remains same shape despite angle/retinal image.

Color constancy

object color remains the same despite lighting changes.

Similarity

similar items are grouped together.

Proximity

objects close together are grouped.

Continuation

tendency to see continuous patterns.

Simplicity

perception favors the simplest organization.

Closure

tendency to fill in gaps to see complete figures.

Monocular cues

depth cues requiring one eye (learned).

Binocular cues

depth cues requiring both eyes (inborn).

Superposition

one object blocks another = perceived closer.

Linear perspective

parallel lines appear to converge with distance.

Aerial perspective

distant objects have less detail due to atmosphere.

Elevation

higher objects appear farther away.

Texture gradient

distant objects appear smoother and less textured.

Shadowing

distant areas appear shadowed.

Motion parallax

nearby objects move faster than distant ones when moving.