Lecture 02 - Vision 1

Question 1

Cornea and sclera

Answer 1

cornea = super organized, distinct planes = clear
sclera = disorganized, randomly oriented= opaque
-though, thick, inelastic collagen, outer wall of eye

Question 2

Anterior chamber (aqueous humour)

Answer 2

between cornea and iris

• clear, watery aqueous humor
• measure this for dilation

Question 3

Iris

Answer 3

vascular muscular diaphragm

• pupil: central opening
• diameter of pupil under neural control (PS, Symp)

Question 4

Lens

Answer 4

proteins (collagen) assembled to be optically clear and flexible
-lens epithelial cells organized front to back organization because size limited

Question 5

Ciliary body

Answer 5

• connects lens to scleral wall
• muscle and secretory epithelium
• neural control of ciliary muscle affects shape of lens, independent of iris/pupil
• lens capsule is under constant pull from ciliary muscle
• relax muscle, lens naturally curl up and change shape –> accomodation

Question 6

Vitreous Chamber/cavity

Answer 6

optically empty gel of hyaluronic acid molecules

-physically supports retina layer to remain in place against scleral wall

Question 7

Retina and Choroid

Answer 7

Neural and vascular layers lining inside of scleral wall

-minimize blood structures blocking vision

Question 8

Optic Nerve

Answer 8

collection of retinal nerve cell axons transmitting info to Lateral Geniculate Body via optive nerve –> optic chiasm –> optic tract –> lateral geniculate body

• outer sheath is contiguous with CNS dura mater
• get myeline so light passage isn’t disturbed
• ganglion cell bodies in retina, axons travel to common exit area and gather into cylinder

Question 9

Hyaloid Canal

Answer 9

Remnant of embryology
-eye starts as tube and develops into sphere
-canal is not visible clinically
(potential structure, not anatomic)

Question 10

Principles of Refraction

Answer 10

At interface of two materials of different optical densities, light bends towards the perpendicular of the surface of the interface
-affect bending by changing curvature of the interface or changing optical densities

• **surface of cornea is more important for light focusing because of the curvature than lens
• largest refraction at air:tear interface

Question 11

Function of the lens

Answer 11

refraction/focusing of image by accomodation

• change lens shape to focus on distant or near images (changing focal distance)
• relaxing ciliary muscle –> lens become more round

Question 12

Accomodation

Answer 12

lens capsule is elastic
-totally relaxed state of lens = round
-ciliary muscle contracts to allow the lens to be more round
- Parasymp:
edinger-westphal –> CN3 –> ciliary ganglion (in eye socket) ***synapse –> ciliary nerve –> ciliary muscle

Question 13

Pulillary Aperture

Answer 13

pupil size important variable in vision

• adapt to amount of ambient light
• smaller pupil = increased depth field = “pinhole effect”
• pinhole minimizes blur of other light rays coming in
• distinguishes between lens refraction angle issues from other issues like optic nerve/retina problems

Question 14

Structure of Pupil

Answer 14

Constrictor

• pupil margin = circular muscle (sphincter pupillae)
• parasymp control (ACh, pilocarpine
• edinger-westphal –> CN3 –> ciliary ganglion –> ciliary nerve –> sphincter

Dilator

• within stroma of pupil = radial muscle (dilator pupillae)
• symp control (epinephrine, congeners)
• pharmacologically parasymp antagonists = dilation (drops for dilation)
• lateral horn –> superior cervical ganglion –> ciliary nerve –> dilator

Question 15

Retinal cell types

Answer 15

4 types of cells

1. Retinal pigment epithelium - support photoreceptors, absorb light and heat (lots of blood, garbage trucks for 2)
2. Rods and cones - change light energy to synaptic energy (physical to chemical)
3. Interneurons - relay, process, modify image signals WITHIN RETINA
4. Ganglion cells - relay, process, modify image signals TO BRAIN (brain can’t interpret if these are lesioned)

Question 16

photoreceptors

Answer 16

convert photons into neural information

Question 17

interneurons & ganglion cells

Answer 17

process and transmit neural info

Question 18

retinal pigment epithelium

Answer 18

support metabolic needs of photoreceptors
heat sink
absorb unprocessed photons

Question 19

Rods

Answer 19

Rods are sensitive (function even in low light)
“white” only - no color perception
great numbers in retinal periphery (image locator)
none in center
wide connections to interneurons - 1000 rods to 1 ganglion
allows sensitivity

Question 20

Cones

Answer 20

insensitive: require much ambient light
color vision (RBG)
greater number in central retina (macula) to give detail and locater analyze function (image resolution)
none in peripheral retina
very narrow connections to interneurons (often 1:1)
allows detail
cell bodies form foveal pit
different cones combine to get different colors

Question 21

Foveal Pit

Answer 21

Mostly cones - RBG analyzer

• age related macular degeneration = color degen
• forms dark circle in the eye because absorbing color, not bouncing light off on the way
• curved fibers

Question 22

Central visual pathways

Answer 22

visual fields
retinal projections
visual cortex

Question 23

Visual fields

Answer 23

receptive areas of retinal cells

• geographically organized –> lateral geniculate body
• split from Right/Left eye into Right/Left fields of vision
• right field, left field overlap = true binocular vision
• right fields and left fields become joined/overlaid at optic chiasm

Question 24

Retinal projections

Answer 24

lateral geniculate = synapse

segregation/retinotopy - right/left and upper/lower

Question 25

Visual cortex

Answer 25

From lateral geniculate body to cortex - optic radiations