ability to perceive stimuli

conscious awareness of stimuli received by sensory neurons

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

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

provide information about body and environment

provide information about internal organs

smell, taste, sight, hearing, and balance

- detect movement • example, touch, pressure, vibration

detect chemicals • example, odors

detect light

detect temperature changes

detects pain

detect light touch and pressure

detect light touch

- deep in epidermis -localizing tactile sensations

- deep tactile receptors - detects continuous pressure in skin

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

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

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

- loss of consciousness - chemicals affect reticular formation

originates in a region that is not source of pain stimulus

thin membrane that covers inner surface of eyelid

produces tears

help move eyeball

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

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

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

contains blood supply

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

helps hold lens in place

flexible disk-focuses light onto retina

colored part - surrounds and regulates pupil

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

covers posterior 5/6 of eye contains 2 layers

outer layer - keeps light from reflecting back in eye

contains photoreceptors (rods and cones) contains interneurons

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

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

photosensitive pigment in rod cells

colorless protein in rhodopsin

- bending of light

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

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

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

where 2 optic nerves connect

route of ganglion axons

-nearsightedness - image is in front of retina

- farsightedness - image is behind retina

lens becomes less elastic reading glasses required

irregular curvature of lens - glasses or contacts required to correct

absence or deficient cones - primarily in males

increased pressure in eye - can lead to blindness

small spot near center of retina

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

-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)

located behind anterior chamber - contains aqueous humor

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

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

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

inner ear - contains utricle and saccule

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

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

dynamic equilibrium - sense movement if any direction

base of semicircular canal

in ampulla

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