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136 terms

A&P Chapter 15 Special Senses

what are three layers of the eye?
fibrous, vascular and sensory
what layer of the eye carries out the eye function?
the sensory layer
what part of the eye focuses?
the lens
what separates the anterior and posterior parts of the eye?
the lens
the five special senses
five special senses all have..
specialized sensory receptors inside sensory organs or epithelial structure
receptor that provides information about the external environment
found in all special senses
the dominant sense in humans
size of an adult human eye
amount of eye exposed in humans
1/6 of anterior
lacrimal apparatus
contains the lacrimal glands and ducts
lacrimal glands
located at the superiolateral corner of eye
produces tears
saline-like with mucus, antibodies, and lysozyme
pathway of tears
enter superiolaterally and exit medially, then drain into nasal cavity
function of eye muscles
move the eye
maintain eye shape
hold in place
extrinsic eye muscles
superior rectus
inferior rectus
medial rectus
lateral rectus
superior oblique
inferior oblique
superior rectus
elevates eye and turns medially
inferior rectus
depresses eye and turns medially
medial rectus
moves eye medially
lateral rectus
moves eye laterally
superior oblique
depresses eye and turns laterally
inferior oblique
elevates eye and turns laterally
muscles that move the eye laterally
lateral rectus
superior oblique
inferior oblique
muscles that move the eye medially
superior rectus
medial rectus
medial rectus
fill the internal cavity of the eye
maintain shape
aqueous humor
watery substance that fills the anterior chamber
supports, nourishes and removes waste
vitreous humor
gel-like substance in posterior chamber of eye
supports lens and holds retina in place
creates pressure to offset pulling of extrinsic muscles
how long does vitreous humor last?
a life time; it forms in embryo
when aqueous humor is made faster than drained
composition of the fibrous layer
made of avascular dense connective tissue
posterior portion of fibrous layer in eye
opaque and white schlera
white off the eye
made of fibrous connective tissue
(posterior end is pierced by optic nerve)
function of sclera
protects eye and anchors extrinsic muscles
anterior part of fibrous layer
made of cornea
anterior part of fibrous layer
allows light to enter the eye
contains lots of touch and pain receptors
what part of the eye contains epithelial cells that renew regularly?
the cornea
when cornea is touched...
...eye will blink automatically
what part of the eye can be transplanted? why?
cornea, because it contains no blood vessels
choroid region
posterior 5/6 of vascular layer in eye
supplies blood to all eye layers
contains melanin to prevent light scattering
ciliary body
anterior 1/6 of vascular layer in eye
a thickened ring of tissue surrounding lens
ciliary muscles
ciliary zonule
ciliary process
ciliary muscles
control shape of lens
part of the ciliary body
ciliary zonule
ligament holding lens in place
ciliary process
radiating folds near lens
secretes aqueous humor
what determines the color of the iris?
central opening of the iris
part of the vascular layer
what regulates amount of light entering the eye?
the pupil
in close vision and bright light the pupil will...
in distant vision and dim light the pupil will...
another name for the sensory layer
the retina
two layers of the retina
pigmented layer
neural layer
pigmented layer in the retina
absorbs and prevents light from scattering
neural layer in the retina
contains photoreceptors and blood vessels
what layer in the eye responses to light?
neural layer of the retina
optic disc
where the optic nerve leaves the eye
why does the optic disc create a blind spot?
there are no photoreceptors on the optic nerve
fovea centralis
contains only cones and has highest visual acuity
cones and rods
bright light receptors
produce high-acuity color vision
what colored cones do humans have?
blue, green and red
all respond to different lights
what causes colorblindness?
a lack of one or more cones types
is genetic
dim light and peripheral vision receptors
sensitivity to light
produce black and white images
which are more common? rods or cones?
rods are more common
structure of the lens
biconvex and flexible
lens becomes dense and less elastic with age
what causes near point of accommodation to increase?
lens becomes cloudy with age
(can be surgically replaced)
pathway of an image
light -> cornea -> aqueous humor -> lens -> vitreous humor -> retina -> photoreceptors -> optic nerve -> cerebral cortex
how is an image flipped through pathway?
up-side-down and right-and-left reversed
what "corrects" a flipped image?
cerebral cortex
emmetropic eye
normal eye with proper focus
myopic eye
nearsighted (can not see far well)
hyperopic eye
farsighted (can not see close well)
chemical senses
gustation and olfaction
chemoreceptors respond to what?
chemicals in aqueous solution
taste - dissolved in saliva
smell - dissolved in nasal mucus
olfactory epithelium
organ of smell
located on the roof of the nasal cavity
olfactory receptors
located on the olfactory epithelium
bipolar neurons
each with dendrite with several olfactory cilia
supporting cells
secrete mucus
surround olfactory receptors
olfactory cilia
extend from dendrites of bipolar olfactory receptors
increase receptive surface area
what is formed by the axons of olfactory receptors?
olfactory nerve
smell stimulates what parts of the brain?
olfactory cortex for interpretation
thalamus for emotional response
if a smell if associated with danger, it will trigger the...
...sympathetic nervous response
if a smell is appetizing...
...saliva will be secreted
if a smell is unpleasant...
...sneezing and coughing reflexes are triggered
organs for taste
taste buds
tongue papille
peg-like projections of the tongue mucosa
where taste buds can be found
types of tongue papille
what is the least functional tongue papille?
foliate (though more active in kids)
what is the most numerous tongue papille?
what is the largest tongue papille?
how many gustatory and basal cells does a taste bud have?
gustatory hairs
extend through taste pore to the epithelial surface
in the mouth, basal cells...
differentiate into new gustatory cells
(stem cells)
how many different smells do humans have?
10, 000
(500 proteins deposited on receptor cells)
five basics tastes
part of the brain that is stimulated by taste
gustatory cortex for recognition
hypothalamus for appreciation (emotional response)
cranial nerves associated with taste
facial - anterior 2/3 tongue
glossopharyngeal - posterior 1/3 tongue
vagus - epiglottis and pharynx
how many different tastes do humans have?
what percentage of taste is actually smell?
what parts of the ear are involved in hearing?
outer and middle parts
what part of the ear is involved in hearing and equilibrium?
inner ear
differences between hearing and equilbrium
have two different receptors
receptors respond to different stimuli
activated independently
parts of the outer ear
auricle and external acoustic meatus
tympanic membrane
outer ear
supported by elastic cartilage
helix and lobule
helix of ear
rim of the outside
part of the auricle
external acoustic meatus
curved tube on the temporal bone
filled with hair, sebaceous glands and ceruminous glands
tympanic membrane
thin, translucent connective tissue membrane
vibrates in response to sound
transfers sounds to middle ear bones
what divides the outer and middle ears?
tympanic membrane
what two openings connect the middle ear with the inner ear?
superior oval window
inferior round window
middle ear
small, air filled, mucosa-lined cavity
superior oval window
connects middle ear to vestibule
inferior round window
connects middle ear to cochlea
auditory tube
connects middle ear to pharynx
usually flattened and closed, opens when yawning
what equalizes middle ear pressure with external air?
auditory tube
bones of the middle ear (ossicles)
malleus, incus and stapes
what transmits eardrum vibrations to the inner ear?
malleus, incus and stapes
vibration of very loud sounds is dampened by...
...two small muscles????
where is the inner located?
deep in temporal bone and behind the eye socket
what is the most complex part of the ear?
the inner ear
bony labyrinth
channels within the bone
vestibule, semicircular canals and cochlea
filled with perilymph
fills the bony labyrinth
membranous labyrinth
membrane sacs within the bony labyrinth
suspended in perilymph
filled with endolymph
what do the fluids of the inner ear do?
conduct sound vibrations (hearing)
respond to mechanical forces during position change (equilibrium)
what is the central cavity of the bony labyrinth?
the vestibule
contains saccule and utricle
houses equilbrium receptors
smaller sac of the vestibule
extends into the cochlea
larger sac of the vestibule
extends into the semicircular canals
equilibrium receptors
respond to gravity and changes in head position
semicircular canals
three canals that define 2/3 of a circle and lie in three planes of space
(90 degrees from each other)
membranous semicircular ducts
line each canal and communicate with the utricle
what part of the semicircular canals house equilibrium receptors?
the swollen ends of the canal
what responds to angular movements of the head?
swollen ends of the semicircular canals
houses hearing receptors spiral organs of corti
spiral bony chamber extending from vestibule
houses cochlear duct that ends at cochlear apex
how many turns does the cochlea take?
about 2.5
what is the dead end of the cochlea?
the cochlear apex
transmission of sound
outer ear (pinna and auditory canal)
tympanic membrane
middle ear bones
oval window
inner ear
cochlear duct
organ of corti
hair cell bending
basilar membrane
action potential in cochlear nerve
nerve cerebral cortex