Vision Flashcards
Surface anatomy of eye
- eyebrows, eyelashes
- PALPEBRAE (eyelids), inferior and superior
- PALPERBRAL FISSURE (opening between eyelids)
- CANTHUS/CANTHI, medial and lateral (where palpebrae meet)
- LACRIMAL CARUNCLE (@ medial canthus
- CONJUNCTIVA (membrane that forms inner membrane of eyelid)
- iris + pupil
structure + function of conjunctiva
STRUCTURE
- membrane that forms inner membrane of eyelid
- folds in on itself up to level of cornea
BULBAR CONJUNCTIVA
(lines white of eye)
PALPEBRAL CONJUNCTIVA
(lines eyelid)
FUNCTION
- prevents debris from moving into posterior eye
- can also respond to infection (pink eye)
Lacrimal Apparatus
LACRIMAL GLAND
- produces tears
LACRIMAL DUCTS
- superior lateral side of eye
- distribute tears from lacrimal glands
tears travel down, but if too many…
PUNCTA
- two small openings @ medial corner of eye
LACRIMAL CANALICULI, superior, inferior
- tubes that collect tears
LACRIMAL SAC
NASOLACRIMAL DUCT
- tears drain into nasal cavity
why does your nose run when you cry?
excess tears directed into nasolacrimal duct and out the nose
6 muscles that control eyeball movement
4 RECTUS MUSCLES
all attached to anterior sclera portion, extend to eye socket (orbit)
- superior rectus
- inferior rectus
above attached at an angle, can also contribute to medial movement
- medial rectus
- lateral rectus
2 OBLIQUE MUSCLES
rotation of eye
- inferior oblique
- superior oblique (runs through trochlea)
3 main layers of eye (TUNICS)
- FIBROUS TUNIC (white of eye)
- SCLERA (posterior)
- CORNEA (anterior) - VASCULAR TUNIC
- contains blood supply and melanin
- CHOROID (posterior)
- CILIARY BODY
- IRIS - RETINA (NEURAL TUNIC)
- contains photoreceptor cells (rods and cones)
sclera structure + function
STRUCTURE
- posterior portion of fibrous tunic
- thick connective tissue layer
FUNCTION
- helps maintain shape of eye
- attachment point for extrinsic eye muscles
- protection
cornea structure + function
STRUCTURE
- anterior portion of fibrous tunic
- transparent + curved
- avascular
FUNCTION
- focus light
ciliary body
- anterior layer in vascular tunic
- contains smooth muscles that change shape of lens
iris changes diameter of
pupil
purpose of melanin in eye and where is it found?
- makes inside surface of eye black
- improves visual acuity by lessening light reflection in eye
- found in vascular tunic
eye movement caused by eye muscles
medial rectus: medial only
lateral rectus: lateral only
inferior rectus: inferior and medial
superior rectus: superior and medial
inferior oblique: superior and lateral
superior oblique: inferior and lateral
blind spot
hole in retina
- allows central retinal artery and vein to enter/exit eye
3 chambers in eye
2 in ANTERIOR CAVITY (in front of lens), filled with AQUEOUS HUMOR
- ANTERIOR CHAMBER (between cornea and iris)
- POSTERIOR CHAMBER (between iris and lens)
1 in POSTERIOR CAVITY (behind lens), filled with VITREOUS HUMOR
- VITREOUS CHAMBER
purpose of aqueous humor
- fills anterior cavity of eye
- helps maintain interocular pressure
- helps maintain shape of eye
- provides nutrients for cornea and lens (both avascular)
- helps with light refraction
flow of aqeuous humor
- produced in cilliary processes
- posterior chamber
- pupil
- anterior chambers
- reabsorbed at edge of cornea
- replenishes every ~90 mins
purpose of vitreous humor
- holds retina layer flat against choroid to create clear images
- helps keep shape of eye
black spots in vision?
debris in vitrous humor
ciliary body structure + function
STRUCTURE
- CILIARY MUSCLE (radial orientation)
- CIIARY RING (circular orientation)
- CILIARY PROCESSES (attached to lens via SUSPENSORY LIGAMENTS)
What happens when different ciliary muscles contract?
Radially oritented - lens widens
Circularly oriented - lens closes
What causes pupil to constrict and dialate?
constrict
- SPHINCTER PUPILLAE (circular muscles) contract
- PNS
dialate
- DIALATOR PUPILLAE (radial muscles) contract
- SNS
target on retina for light entering eye
MACULA LUTEA
and its centre, the FOVEA CENTRALIS (only contains cones)
2 main layers of retina
PIGMENTED LAYER
- pigment cells filled with melanin
NEURAL LAYER
3 layers
- PHOTORECEPTOR LAYER
- BIPOLAR LAYER
- GANGLIONIC LAYER
focal point
where light rays cross in eye to flip image onto retina
How does the eye focus on distant vs near images?
Distant
- light rays come in parallel
- lens flat (tension in suspensory ligaments high, ciliary muscles relaxes)
Near
- divergent light rays
- lens spherical (tension in suspensory ligaments low, ciliary muscles contract)
3 events to bring an image into focus
- ACCOMODATION
- ciliary muscles contract, lens more spherical, greater light refraction - PUPIL CONSTRICTION
- small diameter = greater depth of focus - CONVERGENCE
- as an object moves closer, eyes rotate medially to pick up light rays
rod and cones cells are both ____ cells
bipolar
rod and cone cell structure + function
RODS
- non-colour and low light vision
- RHODOPSIN (photosensitive pigment), made of RETINOL pigment that’s located in OPSIN protein
- light sensitive end cylindrical
CONES
- PHOTOPSIN (red, green, blue)
- light sensitive end conical
BOTH
- connected to Na+ channel
- cell depolarized at rest (Na+ channel open)
why did parents tell you to eat carrots to improve vision?
Vitamin A
retinal made of vitamin A, key component of rods
change in membrane potential with light stimulus
DARK
- Na+ channel held open by cyclic GMP (cGMP)
- Retinol bent (inactive)
LIGHT STIMULUS
- retinol straightens (active)
- phosphodiesterase active - converts cGMP to GMP
- Na+ channel closes, HYPERPOLARIZATION
- retinol detaches, phosphodiesterase inactive, cGMP build up again and opens Na+ channel
How is signal sent through neural layer
- dark condition creates action potential in photoreceptors (depolarized)
- IPSP to biopolar cells via GLUTIMATE
- light stimulus causes hyperpolarization = no action potention, NTs decrease
- bipolar cell activated
- NT towards ganglion cell
- ganglion cell signal to optic nerve
where do visual signals travel to in brain?
- superior colliculi
- lateral geniculate nucleus of thalamus, synapse, then via optic radiations travel ton visual cortex in occipital lobe
