-an unpleasant perceptual and emotional experience -can be localized or diffuse

- deep in epidermis -localizing tactile sensations

detect chemicals • example, odors

colored part - surrounds and regulates pupil

contains photoreceptors (rods and cones) contains interneurons

center of macula - where light is focused when looking directly at an object - only cones - ability to discriminate fine images

- detect movement • example, touch, pressure, vibration

gelatinous substance that moves in response to gravity - attached to hair cell microvilli which initiate action potentials

regulates amount of light entering lots of light = constricted - little light = dilated

originates in a region that is not source of pain stimulus

outer layer - keeps light from reflecting back in eye

produces tears

thin membrane that covers inner surface of eyelid

covers posterior 5/6 of eye contains 2 layers

- loss of consciousness - chemicals affect reticular formation

route of ganglion axons

- bending of light

gelatinous mass - contains microvilli - float that is displaced by endolymph movement

increased pressure in eye - can lead to blindness

- deep tactile receptors - detects continuous pressure in skin

- lens becomes less rounded, and image can be focused on retina - enables eye to focus on images closer than 20 feet

located behind anterior chamber - contains aqueous humor

- transparent structure that covers iris and pupil - allows light to enter and focuses light

-point where light rays converge - occurs anterior to retina - object is inverted

-sense of smell - occurs in response to odorants - receptors are located in nasal cavity and hard palate - we can detected 10,000 different smells

detect temperature changes

help move eyeball

flexible disk-focuses light onto retina

-action potentials suppressed from pain -receptors in local areas -chemicals are injected near sensory nerve

-located in retina region - filled with vitreous humor: jelly-like substance - vitreous humor helps maintain pressure, holds lens and retina in place, refracts light

-white spot medial to macula - blood vessels enter eye and spread over retina - axons exit as optic nerve - no photoreceptors - called blind spot

located between cornea and lens filled with aqueous humor (watery)

leaves eye and exits orbit through optic foramen to enter cranial cavity

irregular curvature of lens - glasses or contacts required to correct

- farsightedness - image is behind retina

contains blood supply

receptors over large part of body that sense touch, pressure, pain, temperature, and itch

- deepest receptors - associated with tendons and joints -detect deep pressure, vibration, position

-photoreceptor sensitive to light - 20 times more rods than cones - can function in dim light

-photoreceptors provide color vision - 3 types: blue, green, red

where 2 optic nerves connect

- associated with vestibule - evaluates position of head relative to gravity

firm, white outer part - helps maintain eye shape, provides attachment sites, protects internal structures

detect light

photosensitive pigment in rod cells

black part (melanin) - delivers 02 and nutrients to retina

colorless protein in rhodopsin

inner ear - contains utricle and saccule

base of semicircular canal

detects pain

ability to perceive stimuli

provide information about internal organs

small spot near center of retina

-nearsightedness - image is in front of retina

provide information about body and environment

conscious awareness of stimuli received by sensory neurons

associated with semicircular canals - evaluates changes in direction and rate of head movement

lens becomes less elastic reading glasses required

detect light touch

dynamic equilibrium - sense movement if any direction

smell, taste, sight, hearing, and balance

- sensory nerve endings that respond to stimuli by developing action potentials

-detect taste -located on papillae on tongue, hard palate, throat

absence or deficient cones - primarily in males

detect light touch and pressure

in ampulla

helps hold lens in place

specialized patches of epithelium in utricle and saccule surround by endolymph contain hair cells