module 3 vision and eye Flashcards
What are the 6 special senses
touch vision, smell, taste, hearing and balance( equilibrium
What makes the special sense “special”
have specialized organs contain receptor cells that are carried by somatic and visceral afferent tracts
What is special about the touch sense
somatic: no specialized sense organ
uses general receptor composed of modified dendrite of sensory neuron
includes: pressure, vibration, pain and heat
What is the eye
organ responsible for sight
What are the 3 layers of the eye
outer
middle
inner
What does outer eye include
posterior: sclera- white of eye
anterior: cornea- transparent- light enters
outer layer is fibrous
What fills the space between the cornea and lens
aqueous humor
What does middle layer of eye include
posterior: choroid
Anterior: ciliary body
Anterior to ciliary body: Iris
In Iris: Pupil
What is notable about choroid
dark colored, prevents light from dispersing throughout the eye
highly vascular and supplies blood to other layers of the eye
What is notable about ciliary body
changes shape of lens allows lens to focus
What is notable about iris
contains circular colored portion of the ye
controls amount of light entering pupil
uses muscle fiber to contract or dilate pupil based on light in environment
Where is pupil found
hold in center of iris
What does the inner eye include
sensory layer
Retina
What does retina contain
contains 2 photoreceptor cells sensitive to light
Rods and cones
Describe the rods of the retina
more numerous amount of cells
stimulated in dim light
more sensitive to light but do not generate sharp or color images
Describe cones of retina
operate in bright light helping to generate sharp color images
less numerous than rods
Where is Lens located
located posterior to iris and pupil
What is vitreous body
found interior of the eye
posterior to lens
chamber filled with fluid
helps hold retina firmly to choroid
Describe the vision pathway
- )light passes through cornea, aqueous humor lens and vitreous humor to the posterior surface of eye on retina
- ) photoreceptors in retina send a signal through optic nerve on optic chiasm
- ) medial fibers of optic nerve cross to other side when they reach optic chasm where optic tract are formed
- ) optic tract terminate in thalamus in lateral geniculate nucleus( LGN)
- ) information continues from thalamus through optic radiations to primary visual area of occipital lobe
- ) once in occipital lobe incoming sensory info interpreted as vision
Where does each eye receive information from
Left and Right sides of the body
What is the nasal visual field
field closes to the nose
What is peripheral field of vision
lateral side of each eye
What is the Binocular visual field
overlapping info in nasal fields allow for 3-D vision
what is the L bilateral vision field
sensory information for L side of body
eventually interpreted on R side of brain
medial fibers are only ones that cross at optic chiasm
What is R bilateral vision field
sensory information for R side of body
eventually interpreted on L side of brain
medial fibers are only ones that cross at optic chiasm
How does L side brain receive information
received from bilateral R visual field
receives info from medial side of L eye and lateral side of R eye
How does R side of brain receive information
received from L bilateral visual field
receive info from medial side of R eye and lateral side of L eye
Eye movements are controlled by which 6 extrinsic eye muscles
medial rectus, inferior rectus, superior rectus, inferior oblique, superior oblique, lateral rectus
What does medial rectus do
turns eye medially
what does inferior rectus do
turns eye medially and depresses the eye
what does superior rectus do
move eye medially and raises the eye
what does inferior oblique muscle do
controls eye elevation, lateral movements and external rotation
Which nerve innervates medial rectus, inferior rectus, superior rectus and inferior oblique
CN III- oculomotor
what is function of superior oblique muscle and which nerve is it innervated by
eye depression, internal rotation, lateral movement
CN IV- trochlear
What is function of lateral rectus and which nerve is it innervated by
abducts the eye
CN VI- abducen
How do visual impairments occur
from damage to any part of vision pathway
What are cataracts
lenses slowly harden and get cloudy over time
make vision look blurry as light is unable to enter lens clearly to be refracted onto retina
What are other sources of injury that cause eye impairments
damage inside the brain- CVA, tumors etc
Can cranial nerves be damaged
yes
example: CN VI- abducen
if damaged would cause diplopia
what is diplopia
double vision
What is a test for CN VI damage
have patient look L and R while keeping head still
If lateral rectus does not receive signal from abdomen eye won’t rotate laterally when look to same side
Affected eye deviates medially when looking forward- will see imbalance in muscle tone in medial and lateral recti
What is the primary auditory sense organ for hearing
organ of corti
What are the 3 regions of the ear
external, middle, inner
What makes up the external ear
auricle and external acoustic canal
Describe the auricle
shaped to funnel sound waves into external acoustic canal so sound is detected
part of ear seen externally
composed of cartilage with thin skin make rim and lobules
What is helix
rim of external ear
do lobules have cartilage
no
Describe external acoustic meatus( canal)
tunnel between auricle and tympanic membrane
composed of elastic cartilage near auricle and become a cylinder through temporal bone
canal lined with skin contains hair and glands secrete cerumen
inner end of canal terminate at tympanic membrane
thin connective tissue membrane vibration transmit sound to middle ear
what is cerumen
ear wax
traps foreign particles from entering external acoustic meatus
Describe middle ear
tympanic cavity
air filled chamber containing 3 smallest bones in the body
what are the 3 bones in the middle ear
malleus- hammer
incus- evil
stapes-stirrup
How do the 3 bones in middle ear function for sound
malleus receive information( vibrates) from eardrum
transfers along through the incus
then stapes which sends to inner ear
Describe the inner ear
bony and membranous labyrinth filled with fluid
Labyrinth divided into 3 sections: vestibule, semicircular canal, cochlea
Describe the vestibule structure and function
connects to 3 semi-circular canal
houses receptors to provide body vestibular( balance and equilibrium)
Describe the semicircular canals
filled with fluid
each canal has receptors which cause action potential in response to stimuli( motion)
action potential set through vestibular portion of CN VIII
contributes to body vestibular sense: balance and ability to stay upright
Describe structure and function of cochlea
spiny bone chamber
contains endolymph filled with cochlear duct
houses organ of corti and ends at cochlear nerve
Which other CN is found in inner ear
CN VII- facial
innervates stapedius muscle
Describe structure and function of stapedius muscle
attaches to stapes
controls amount of tension on the bone allow for increase or decrease of vibration to control intensity of sound
What is structure and function of organ of corti
serves as organ auditory system
contains tectorial membrane and tiny hairs called sterocilia
as fluid in cochlearduct receives vibrations, tectorial membrane moves and bends attached steriocilia
mechanical movement indicates action potential in neuron transmitted through cochlear portion of CN VIII
Describe the process of hearing
- ) sound wave funneled into external auditory canal causing eardrum to vibrate
- ) vibrations transmit to ossicle-> push against fluid in cochlear duct
- ) movement of fluid-> cause movement of steriocilia in organ of corti
- ) movement of steriocilia stimulate neuron to send impulse through cochlear nerve to primary auditory cortex of temporal lobe
- ) auditory pathway unique sensory pathway as ascending path cross in addition to send signal to same side of brain
6) results-> sound from each each are = interpreted on L and R side of the brain
Define deafness
damage to auditory pathway results in hearing loss
can be partial or total loss
What is conduction deafness
damage to outer or middle ear structures
not considered complete deafness as sound waves can be conducted through cranial bones to move organ of corti
What are examples of conduction deafness
cerumen partially block sound waves from entering external acoustic meatus
ossicle bones fused-> decreased amount vibration transmitted to inner ear
What is nerve deafness
damage to nerve pathway
damages occur to receptor cells or to cochlear nerve
can be partial or complete in one or both ear depending on amount of damage to nerve pathway
Define olfaction
ability to smell
an is one of special chemical senses
How are olfactory senses activated
by air borne chemicals dissolved in fluid on surface of nasal mucous membrane
Which CN is associated with smell and where are receptors found
CN 1
bipolar receptor cells found in olfactory epithelium on roof of nasal cavity
Describe the process for smell
- ) CN 1 travels through ethmoid bone in cribiform plate
- ) Dendrites extend from cell body to surface of epithelium and terminates in olfactory bulb
- ) In olfactory bulb-> CN 1 axon synapse with other cell body of olfactory pathway
- ) axons travel together to form olfactory tract-> carry info to temporal lobe
- ) after getting too temporal lobe is interpreted as smell
What are the olfactory bulbs
masses of grey matter
What is smell composed of
combination of limited # of primary odor detectable by brain
isolated into 7 primary odors
What are the 7 primary odors
floral ethereal- (dry cleaning fluid) camphorate- (moth ball) musky( perfume) peppermint (mint gum) pungent( vinegar) Putrid ( rotten egg)
What is the gustatory system
responsible for taste
Define taste
chemical sense as receptor activated by chemical dissolved in saliva
Where are taste receptors found
mostly on tongue but also through mouth and throat
What is the function of the tongue
responsible for gripping food and reposition in between teeth forming bolus
tongue pushes bolus back to phalanx to being process of swalling
What is apex of tongue
anterior portion
what is root of tongue
located attached to floor of posterior surface of mouth
Where is frenulum
located on inferior surface of the tongue along midline
What are papillae
raised bumps on tongue
3 types
What are the 3 types of papille
circumvallate
fungiform
filiform
How are taste buds formed
chemical receptors stimulated by composition of food- formed from gustatory cells and supporting cells
What are gustatory cells
chemoreceptor cell inside taste bud- terminates in gustatory hair, project saliva to detect chemicals
What are supporting cells for taste bud
form bulk of tastebud, separate receptor cell from each other
What are basal cells for taste bud
stem cells
divide and become new support cell the gustatory
What are the 2 receptors for the mouth
nociceptor- pain
thermoreceptor-temp
contribute to taste experience
temp and spice impact taste perception
What is the taste pathway
- ) food contacts gustatory hairs, generate action potential in dendrites wrapped around gustatory cells
- ) nerve signal carried by afferent fiber through CN VII and CN IX- facial and glossopharyngeal
- ) transmits signal to thalamus then to parent for interpretation
Where does CN VII carry information to
facial: 2/3 of anterior of tongue
Where does CN IX carry information to
glossopharyngeal information posterior 1/3 tongue
What are the 5 primary taste
sweet- produced sugar and amino acid salty- metals especially NaCL sours- acids like aseptic acid( vinegar) bitter- drugs like aspirin savory- due to amino acids found in food like fish, ripe tomato, aged cheese and soy sauce
What is anosmia
loss of smell
common after TBI
can be temporary or permanent
Can also happen gradually- brain tumor block olfactory pathway
What is ageusia
loss of taste
stimulation of olfactory receptors have great impact on sensation of taste
when olfactory receptor is block by nasal congestion
sense of taste is dulled or completely lost
TBI/ brain time can cause this if pathway is damaged
