Vision

Question 1

Surface anatomy of eye

Answer 1

• 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

Question 2

structure + function of conjunctiva

Answer 2

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)

Question 3

Lacrimal Apparatus

Answer 3

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

Question 4

why does your nose run when you cry?

Answer 4

excess tears directed into nasolacrimal duct and out the nose

Question 5

6 muscles that control eyeball movement

Answer 5

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)

Question 6

3 main layers of eye (TUNICS)

Answer 6

1. FIBROUS TUNIC (white of eye)
   - SCLERA (posterior)
   - CORNEA (anterior)
2. VASCULAR TUNIC
   - contains blood supply and melanin
   - CHOROID (posterior)
   - CILIARY BODY
   - IRIS
3. RETINA (NEURAL TUNIC)
   - contains photoreceptor cells (rods and cones)

Question 7

sclera structure + function

Answer 7

STRUCTURE
- posterior portion of fibrous tunic
- thick connective tissue layer
FUNCTION
- helps maintain shape of eye
- attachment point for extrinsic eye muscles
- protection

Question 9

cornea structure + function

Answer 9

STRUCTURE
- anterior portion of fibrous tunic
- transparent + curved
- avascular
FUNCTION
- focus light

Question 10

ciliary body

Answer 10

• anterior layer in vascular tunic
• contains smooth muscles that change shape of lens

Question 11

iris changes diameter of

Answer 11

pupil

Question 12

purpose of melanin in eye and where is it found?

Answer 12

• makes inside surface of eye black
• improves visual acuity by lessening light reflection in eye
• found in vascular tunic

Question 13

eye movement caused by eye muscles

Answer 13

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

Question 14

blind spot

Answer 14

hole in retina
- allows central retinal artery and vein to enter/exit eye

Question 15

3 chambers in eye

Answer 15

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

Question 16

purpose of aqueous humor

Answer 16

• 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

Question 17

flow of aqeuous humor

Answer 17

• produced in cilliary processes
• posterior chamber
• pupil
• anterior chambers
• reabsorbed at edge of cornea
• replenishes every ~90 mins

Question 18

purpose of vitreous humor

Answer 18

• holds retina layer flat against choroid to create clear images
• helps keep shape of eye

Question 19

black spots in vision?

Answer 19

debris in vitrous humor

Question 20

ciliary body structure + function

Answer 20

STRUCTURE
- CILIARY MUSCLE (radial orientation)
- CIIARY RING (circular orientation)
- CILIARY PROCESSES (attached to lens via SUSPENSORY LIGAMENTS)

Question 21

What happens when different ciliary muscles contract?

Answer 21

Radially oritented - lens widens
Circularly oriented - lens closes

Question 22

What causes pupil to constrict and dialate?

Answer 22

constrict
- SPHINCTER PUPILLAE (circular muscles) contract
- PNS

dialate
- DIALATOR PUPILLAE (radial muscles) contract
- SNS

Question 23

target on retina for light entering eye

Answer 23

MACULA LUTEA
and its centre, the FOVEA CENTRALIS (only contains cones)

Question 24

2 main layers of retina

Answer 24

PIGMENTED LAYER
- pigment cells filled with melanin
NEURAL LAYER
3 layers
- PHOTORECEPTOR LAYER
- BIPOLAR LAYER
- GANGLIONIC LAYER

Question 25

focal point

Answer 25

where light rays cross in eye to flip image onto retina

Question 26

How does the eye focus on distant vs near images?

Answer 26

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)

Question 27

3 events to bring an image into focus

Answer 27

1. ACCOMODATION - ciliary muscles contract, lens more spherical, greater light refraction 2. PUPIL CONSTRICTION - small diameter = greater depth of focus 3. CONVERGENCE - as an object moves closer, eyes rotate medially to pick up light rays

Question 28

rod and cones cells are both ____ cells

Answer 28

bipolar

Question 29

rod and cone cell structure + function

Answer 29

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)

Question 30

why did parents tell you to eat carrots to improve vision?

Answer 30

Vitamin A retinal made of vitamin A, key component of rods

Question 31

change in membrane potential with light stimulus

Answer 31

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

Question 32

How is signal sent through neural layer

Answer 32

- 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

Question 33

where do visual signals travel to in brain?

Answer 33

- superior colliculi - lateral geniculate nucleus of thalamus, synapse, then via optic radiations travel ton visual cortex in occipital lobe