special senses Flashcards
where are no rods or cones found
blind spot
cones function?
color vision
rods function
light vision
where are the most rods found
retina edges
(peripheral vision)
where are the most cones found
fovea
how is the eye test numbered
(first 20 and second twenty mean)
20/20
first 20 means how far you are standing
second 20 means how far the average person is standing to see the same vision as you
which is worse 20/25 or 20/15
20/25
what is myopia
nearsideness
Second number on eye test is bigger than first (20/100)
focused in front of retina
Hyperopia
farsightedness
not tested by eye test
focused behind retina
Emmetropia
normal vision 20/20
focused correctly on retina
3 layers of the eye
fibrous, vascular, sensory
whats in fibrous layer
sclera and cornea
whats in vascular layer
choroid, ciliary body and iris
whats in sensory layer
consists of retina and optic nerve
sclera
white of eye- protection (fibrous layer)
choroid
provides blood supply to eye and absorbs/prevents light from scattering (vascular layer)
fovea centralis
contains only cones; best, most acute day vision is here
optic nerve
cranial nerve II- formed from axons of ganglion cells and sends visual information to the brain structures
optic disk
“blind spot-“ area where there are no rods and cones, where the optic nerve is exiting the eye
vitreous humor
(does it get drained and replaced)
prevents the eyeball from collapsing; found posterior to the lens (you are born with all you will have; it does not get replaced)
aqueous humor
(does it get drained and replaced)
maintains the internal pressure of the eye and provides nutrients to the lens and cornea (gets constantly drained and replaced; anterior to lens)
clear watery fluid
lens
“focuses” the image on the retina
pupil
opening through iris through which light passes
iris
regulates the amount of light entering the eye (size of pupil) (part of vascular layer)
cornea
protects eye and has lots of nerve endings (pain sensors)- avascular so can be transplated to anyone without rejection
ciliary body
changes the shape of the lens for focusing near and far
ciliary zonule
attaches the ciliary body muscle to the lens
conjunctiva
connects to the outer surface of the eye and secretes mucus to keep the eye moist. (“pink” eye occurs here)
lacrimal gland
produces tears to moisten and protect the eye
whats in the external (outer) ear
pinna, auditory canal, up to tympanic membrane
whats in middle ear
air-filled between the tympanic membrane and the inner ear; contains ossicles (often confused with inner ear)
whats in inner ear
bony labyrinth filled with fluid (perilymph)- contains cochlea and semicircular canals
pinna
directs sound waves into the auditory canal
tympanic membrane
vibrates to transmit sound waves to ossicles
auditory canal (external acoustic meatus)
Contains wax to trap foreign bodies and protect against water and insects.
ossicles
small bones in the middle ear that transmit sound from the outer ear to the inner ear
auditory (eustachian) tube
equalizes pressure between middle ear and atmosphere; is normally closed but swallowing and yawning open it temporarily
round window
allows the perilymph (fluid) to transmit the “wave” of sound
oval window
transmitting the sound wave to the perilymph (liquid) entrance to inner ear aka vestibule
semicircular canals
NOT involved in hearing
BALANCE AND SENSORY INFO
auditory nerve
vestibulocochlear nerve (VIII) 6 transmits sound to from the ear to the brain + hearing and balance
part of the brain that processes sound
temporal lobe
vestibule
transmits sound waves through perilymph (fluid) AND plays a role in balance (static equilibrium) and entrance to inner ear (round window)
