Chapter 15- Vision Flashcards
what are the accessory structures of the eye?
- palpebrae
- levator palpebrae superioris
- conjunctiva
- lacrimal apparatus
- extrinsic eye muscles
function of palpebrae
- eyelids
- superior and inferior structures
- meet at medial commissure and lateral commissure
function of conjunctiva
- palpebral and bulbar conjunctiva
- makes lubricating fluid
what is pterygium?
pinkish tissue growth of the conjunctiva over the front of the cornea
lacrima apparatus function
- cleans and lubricates the eye
- antibacterial
Pathway of lacrimal apparatus
- lacrimal gland produces and secretes tears
- tears enter the conjunctival sac via the excretory ducts of the lacrimal gland
- tears flow down and across the eyeball
- tears enter the lacrimal canaliculi at openings called lacrimal puncta
- tears drain into the lacrimal sac
- from the lacrimal sac, tears empty via the nasolacrimal duct into the inferior meatus of the nasal cavity
functions of extrinsic eye muscles
move the eye
what are the names of the extrinsic eye muscles
lateral rectus
medial rectus
superior rectus
inferior rectus
inferior oblique
superior oblique
lateral rectus
- action and controlling cranial nerve
- moves eye laterally
- VI abducens
medial rectus
- action and controlling cranial nerve
- moves eye medially
- III oculomotor
superior rectus
- action and controlling cranial nerve
- elevates eye and turns it medially
- III oculomotor
inferior rectus
- action and controlling cranial nerve
- depresses eye and turns it medially
- III oculomotor
inferior oblique
- action and controlling cranial nerve
- elevates the eye and turns it laterally
- III oculomotor
superior oblique
- action and controlling cranial nerve
- depresses eye and turns it laterally
- IV trochlear
levator palpebrae superioris function
opens the eye
what are the layers of the eye
- fibrous tunic: sclera and cornea
- vascular tunic: iris, ciliary body, choroid
- neural tunic: retina and optic nerve
ciliary body function
pulls on suspensory ligaments and results in changing the shape of the lens
iris
regulates the amount of light that enters the eye
- color depends on the amt of melanin
more melanin—>darker eyes
Sclera
white of the eye that is covered by the conjunctiva
orbicularis oris muscle
helps close the eye
cornea
focusing most of the light entering the eye by bending it
choroid
structure that supplies blood to eye (outer layers of retina, macula, and optic nerve)
muscle layers of the iris
sphincter (constricts pupil)
dilator (opens pupil)
lens function
allow light to pass through and focuses light onto retina
the lens makes light focus based on how far away things are. t or f
t
what are the three chambers/cavities of the eye
anterior chamber, posterior chamber, and vitreous chamber
what kind of fluid is found in the anterior and posterior chambers?
aqueous humor
- very liquidy
what kind of fluid is found in the vitreous chamber?
vitreous humor
- jello-like
function of the anterior chamber
has aq humor that nourishes the eye
function of vitreous chamber
vitreous humor that helps keep the eye inflated and holds the retina in place
how is aq humor made?
made by ciliary body and goes into anterior segment then it drains into scleral venous sinus and will take it back into circulation into blood stream
what happens if the scleral venous sinus gets blocked?
more fluid build up and make cornea bulge out —-> this is glaucoma
features of the retina
macula lutea and optic disc
macula lutea function
focal point of the retina
fovea centralis is the bulls eye so when we are looking at something it is focusing on the fovea centralis
optic disc function
connection point for the optic nerve
- located at the back of the retina
why is the optic disc a blind spot?
it doesnt contain any rods or cones to detect light rays
lens function
- it is biconvex
- focuses light passing through pupil onto retina
- image projected backwards and upside down
ciliary body relaxation
tightens ligaments —> lens thinner for distance vision
ciliary body contraction
relaxes ligaments –> lens thickens for close-up vision
factors that affect light perception
refraction, accommodation, convergence
refraction
light is bent as it passes through different media
accommodation
lens shape focuses light on macula despite refraction
convergence
moving eyeballs medially or laterally to accommodate objects that are close or far
photoreceptors
sensory receptors for light.
rods and cones
cones
- theres red, blue, and green cones
- color vision
- low sensitivity to light waves
- located in fovea centralis
- respond to stimulation by bright light (day vision)
- provide color recognition and sharpness of vision
rods
- shades of gray
- theres more of them than cones
- high sensitivity to light waves
- located in peripheral retina
- specialized for dim light, night vision
- cannot distinguish color; poor sharpness of vision
phototransduction
conversion of light energy into neural signals
- voltage gated calcium channels close and no glutamate is released
- the bipolar cell is no longer inhibited and depolarizes
- bipolar cell releases NT
- NT binds to receptors in the ganglion cell and a nerve signal is initiated to the brain
afferent pathway for vision
- retina - photoreceptors and neurons in the retina process the stimulus from incoming light
- optic nerve - axons of retinal ganglion cells form optic nerves and exit the eye
- optic chiasm - optic nerve axons from the medial region of the retina cross at the optic chiasm; the axons from the lateral region of the retina remain uncrossed
- optic tract - the optic tract contains axons from both eyes, and these axons will project to either the thalamus or the midbrain
- primary visual cortex of occipital lobe
- then it goes to visual association cortex
fibers from medial side of left eye are processed by the right side of the brain and medial side of right eye is processed by left side. t or f
T
