vision i

Question 1

Visible light

Answer 1

400-700 nm

-vision converts (transduces) stimulus of light into a nervous impulse

Question 2

The eye and vision

Answer 2

• 70% of body’s sensory receptors are in eye
• visual processing by ~ half cerebral cortex
• most of eye is protected by cushio of fat and bony orbit

Question 3

Eye accessory structures

Answer 3

Palpebrae = eyelids (meet at commisures)
Eyelashes and eyebrows
extrinsic eye muscles

these structures protect and asist sensory structures of eye, but aren’t part of eye proper

Question 4

Eyebrows

Answer 4

• overlie supraorbital margins

- func: shade eye from sunlight and prevent sweat from goin in eye

Question 5

Eyelids

Answer 5

• protect eye anteriorly
• separated at palpebral fissure
• meet at medial and lateral commissures
• lacrimal caruncle = @ medial commissure–> has oil and sweat glands
• tarsal plate = supporting CT

Question 6

Eyelashes

Answer 6

-nerve endings of follicles initiate reflex blinking

• lubricating glands associated with eyelids:
  1) Tarsal (Meibomian) gland = modified sebaceous glands whose oily secretions lubricate lid and eye –> infection = chalazion

2)Ciliary glands b/t hair follicles = modified sweat glands –> infection = stye

Question 7

Conjunctiva

Answer 7

• transparent mucous membrane
• produces lubricating mucous secretion
• palpebral conjunctiva lines eyelids
• bulbar onjunctiva covers white of eyes
• conjunctival sac b/t palpebral and bulbar conjunctiva

Question 8

Lacrimal Apparatus

Answer 8

-tears from lacrimal apparatus:

lacrimal glands–> excretory lacrimal duct –> lacrimal puncta –> lacrimal canaliculi –> lacrimal sac –> nasolacrimal duct

Question 9

Extrinsic eye muscle

Answer 9

cranial nerve III (oculomotor)
-superior rectus (superior/medial)
-inferior rectus (inferior/medial)
-medial rectus (medial)
inferior oblique (superior/lateral)

cranial nerve IV (trochlear)
-superior oblique (inferior/lateral)

cranial nerve VI (abducens)
-lateral rectus (lateral)

Question 10

3 layers of the eyeball

Answer 10

1. Fibrous tunic = outer layer
   - sclera “white” of eye
   - cornea - transparent coat
2. Vascular tunic/uvea = middle
   - choroid
   - ciliary body w/ processes and muscels
   - iris
3. Retina = inner
   - pigmented layer
   - neural layer with optic disc and macula lutea/fovea centralis

Question 11

Sclera

Answer 11

• posterior, white, dense irregular CT
• avascular
• protective covering
• provides shape
• sturdy anchor for extrinsic eye muscles (insertion)

Question 12

Cornea

Answer 12

-anterior
-2 epithelial layers
-avascular
-transparent to let light thru
-pain receptors
-regeneration + repair
(lots of refraction)

Question 13

Scleral venous sinus

Answer 13

• “canal of Schlemm)
• at junction of sclera and cornea
• fluid drains from anterior cavity of eye into blood

Question 14

Choroid

Answer 14

posterior to ciliary body

• blood vessels
• pigments (melanocytes) absorb light rays

Question 15

Ciliary body

Answer 15

• anterior to choroid
• ciliary processes = secrete aqueous humor made of filtrate from capilaries
• ciliary muscles = smooth muscle that alters lens shape –> alters tension of suspensory ligaments (ciliary zonules)

Question 16

Iris

Answer 16

-colred part (variations of brown pigment)

smooth muscles

• circular (sphincter pupillae/ pupillary constrictor) –> parasymp
• radial (dilator pupillae/pupillary dilator) –> symp

Question 17

Pupil

Answer 17

• central black hole
• size determines amt of light entering eye
• change in response to bright/dim light or emotions

Question 18

Pigmented layer of retina

Answer 18

• outer layer
• nonvisual
• next to choroid layer
• absorbs stray light
• phagocytes
• stores vit A

Question 19

Neural layer of retina

Answer 19

• inner layer
• visual

3 zones of neurons (post to ant)

• photoreceptors (rods and cones)
• bipolar cells
• ganglion cells (axon exit as optic nerve at optic disc=blind spot= no photoreceptors
• amacrine and horizontal cells modify elec. signals
• macula lutea and fovea centralis have a ton of cones for visual acuity
• ora serrata = boundary of photosensitive area

Question 20

Interior of eyeball (parts)

Answer 20

lens
anterior cavity
posterior cavity

Question 21

lesn

Answer 21

lacks blood vessels

• consists of a capsule with proteins (crystallins) in layers
• transparent

-divides eyeball into anterior and posterior cavities

Question 22

anterior cavity

Answer 22

• divided into anterior and posterior chambers
• both filled with aqueous humor
• aqueous humor is constantly refreshing

Question 23

posterior cavity

Answer 23

• “vitreous chamber”
• filled with jelly-like vitreous humor/ vitreous body
• vitreous humor is permanent

Question 24

Circulation of aqueous humor

Answer 24

1. forms by filtration from capillaries in ciliary processes
2. flows from posterior chamber, thru pupil, to anterior chamber (some also flows thru vitreous humor)
3. reabsorbed into venous blood by scleral venous sinus