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macula lutea

-yellowish spot in the central region of the retina
-includes the fovea centralis which produces the sharpest vision

visual receptors

-modified neurons
-rods & cones
-in the retina

taste cells

-gustatory cell
-group of modified epithelial cells that function as receptors

visceral pain results from what

(1) stimulation of mechanoreceptors
(2) decreased blood flow, causing lower tissue oxygen concentration
(3) accumulation of pain-stimulating chemicals


-image that forms on the retina is upside down and reversed from left to right
-visual cortex interprets the image in its proper position


pigment (visual purple) found in rods


tiny structure in the vestibule that contain hair cells that serve as sensory receptors

choroid coat

contains pigments that absorb excess light and help keep the inside of the eye dark

conductive deafness

interference with the transmission of vibrations to the inner ear

taste hair

extend from taste pore and are the sensitive parts of the receptor cells


eye disorder that develops when aqueous humor formation exceeds the rate it is removed causing fluid pressure to rise, squeezing shut blood vessels

characteristics of referred pain

-common in visceral pain
-occurs when you have common nerve pathways that carry sensory impulses from the skin areas as well as the organs causing the cerebral cortex to incorrectly interpret the source of the pain impulses

pupil dilation

-radial muscles of the iris contract
-occurs in dim light


-long, thin projections at their ends
-hundreds of times more sensitive to light and can provide vision in dim light
-produces colorless vision
-provide more general outlines, less precise images

movement of light

cornea > aqueous humor > lens > vitreous humor

accessory organs of the eyes

eyelids, lacrimal apparatus, extrinsic muscles

taste pore

opening on the free surface of the taste bud


stimulated by light energy

tympanic cavity

air-filled space in the temporal bone


-not as sensitive to light
-produces color vision
-provide sharp images
-pigments: erythrolabe, chlorolabe, & cyanolabe


-tympanic membrane
-sound waves enter the external auditory meatus changing the pressure on the eardrum, which moves in response, reproducing the vibrations


feeling that occurs when the brain interprets sensory impulses


pigment sensitive to red light waves in cones

aqueous humor

-watery fluid secreted by the inner surface of the ciliary body
-fills the space between the cornea and lens, helps nourish these parts, and aids in maintaining the shape of the front of the eye


stimulated by changes in the chemical concentration of substances

structure of the eye

hollow, spherical structure with three distinct layers: inner tunic, middle tunic, and outer tunic


circular opening in the center of the iris


-transparent window of the eye
-helps focus entering light rays
-contains few cells and no blood vessels

pain receptors

stimulated by tissue damage


pigment in cones sensitive to green light waves


-white portion of the eye
-protect the eye and is an attachment for the extrinsic muscles


stimulated by changes in pressure or movement

lacrimal apparatus

secretes tears that exit through tiny tubes & flows downward and medially across the eye

optic disk

-area where nerve fibers from the retina leave the eye and join the optic nerve
-has no receptor cells and is known as the blind spot

sensorineural deafness

damage to the cochlea, auditory nerve, or auditory nerve pathways


increase or amplify the force of vibrations


-tear enzyme
-an antibacterial agent to reduce the risks of eye infections

viewing closer objects

tension relaxes on suspensory ligaments & the elastic capsule rebounds and the lens becomes more convex

acute pain fibers

-thin, myelinated fibers that conduct impulses rapidly and are associated with sharp pain
-usually sensed as coming only from the skin
-seldom continue after stimulus stops


-contain photoreceptors
-also includes: macula lutea & fovea centralis

middle ear

tympanic cavity, eardrum, auditory ossicles, and auditory tube


-helps protect the eye
-4 layers: skin, muscles, connective tissue, & conjunctiva


-complex system of communicating chambers and tubes
-includes: osseous labyrinth, membranous labyrinth, perilymph, & endolymph

outer tunic

-also called the fibrous tunic
-includes: cornea & sclera

inner tunic

includes: retina, optic disk, & posterior cavity

middle tunic

-also called vascular tunic
-includes: choroid coat, ciliary body, & iris

external ear

-include: auricle & external auditory meatus
-vibrating objects produce sounds and are transmitted through matter in the form of sound waves

olfactory bulbs

where impulses are analyzed and then additional impulses move through tracts to the limbic system

olfactory stimulation

the shapes of gaseous molecules fit complementary shapes of membrane receptor sites on these receptor cells, so a molecule binding to its receptor site triggers a nerve impulse

taste nerve pathways

sensory impulses travel on fibers of the facial, glossopharyngeal, and vagus nerves into the medullary oblongata from there they go to the thalamus and are directed to the gustatory cortex

5 types of sensory receptors

chemoreceptors, pain receptors, thermoreceptors, mechanoreceptors, and photoreceptors

auditory ossicles

malleus, incus, and stapes

auditory nerve pathways

nerve fibers enter the auditory nerve pathways, which pass into the auditory cortices of the temporal lobes of the cerebrum


-function in hearing
-contains: scala vestibuli, scala tympani, round window

olfactory receptor cells

bipolar neurons surrounded by columnar epithelial cells

somatic senses (3 kinds of receptors)

sensory nerve fibers, Meissner's corpuscles, and pacinian corpuscles

organ of Corti

located on the upper surface of the basilar membrane and contain the hearing receptors


contains organs of static equilibrium: utricle & saccule


ability of the lens to adjust shape to focus

crista ampullaris

sense organs for dynamic equilibrium


-a thin diaphragm made of connective tissue and smooth muscle fibers
-colored portion of the eye

oval window

-an opening in the wall of the tympanic cavity that lead into the inner ear
-vibrations of stapes at the oval window moves a fluid in the inner ear, stimulating hearing receptors


-cerebral cortex sends the sensation back to its apparent source allowing you to pinpoint the area of stimulation
-allows your eyes to see and your ears to hear

semicircular canals

detect motion of the head and aid in balancing the head and body during sudden movement


stimulated by changes in temperature

taste buds

special organs of taste on the surface of the tongue, roof of the mouth, and walls of the pharynx


swelling in the end of the semicircular canals that contain sensory organs (crista ampullaris)


-partial or complete loss of smell
-results from inflammation of the nasal cavity lining from respiratory infection, tobacco smoking, or use of certain drugs


fluid in the membranous labyrinth


fluid between the labyrinth


pigment in cones sensitive to blue light waves

chronic pain fibers

-thin, unmyelinated fibers that conduct impulses slower and produce a dull, aching pain
-often difficult to pinpoint and can be felt in deeper tissues as well as the skin

extrinsic muscles

-move the eye in various directions
-include: superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique, and inferior oblique

path of pain nerve fibers

impulses starting from the head reach the brain on cranial nerves all others travel through spinal nerve

pupil contraction

-circular muscles of the iris contract
-occurs in bright light

olfactory receptors

-stimulated when chemicals are dissolved in a liquid

auditory tube

-Eustachian tube
-helps maintain equal air pressure on both sides of the eardrum
-mucous membrane infections of the throat may spread through these tubes and cause middle ear infections

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