Hirsch - Eye Flashcards Preview

Neurobiology > Hirsch - Eye > Flashcards

Flashcards in Hirsch - Eye Deck (26):
1

Surface features of the eye

Sclera - Iris - Pupil

2

Eyeball

Cornea & Sclera
Aqueous humor in anterior chamber
Ciliary muscle & choroid
Retina
Iris & Pupil
Ciliary muscle & Zonule fibers & Lens
Vitreous humor (jelly-like)
Fovea
Optic disk

3

Choroid

nourish neural part of eyeball; rods and cons

4

Focal planes with respect to the retina

Emmetropia
Myopia - nearsighted
Hyperopia - far sighted

5

ciliary muscle contract, springs (zonule fibers) .... the lens ....

when ciliary muscle contract,
zonule fibers become loose
lens focuses close object to retina

6

ciliary muscle relax, spring (zonule fibers) .... the lens ....

when ciliary muscle relax,
zonule fibers become tight,
lens focuses distant object to retina

7

myopia or nearsighted when...

eye too long
lens too round
need concave lens

8

hyperopia or far-sighted

eye too short
lens too flat
need convex lens

9

Why are rods and cons far back near choroid?

high metabolic demands
choroid nourishes the cells

10

Basic Retinal Anatomy from proximal to distal

*light come in*
---- inner limiting membrane
---- nerve fiber layer
ganglion cell layer(ganglion cells)
inner plexiform layer(amacrine cells)
inner nuclear layer (bipolar cells)
outer plaxiform later(horizontal cells)
outer nulear layer (muller cells)
---- outer limiting membrane
photoreceptor layer (rods, cones, pigment epithelium)

11

thickness of retina

thick centrally and thin peripherally

12

the fovea

visual acuity maximized
cones only - smaller dense
* outer cones largerand less dense
* outer rods max around fovea and decrease (due to thinner retina)
foveal pit (around: foveal slope)

13

Disease in retina

macular (foveal pit, foveal slope, para & peri fovea) degenration
retinitus pigmentosa
diabetic retinopathy

14

disks in conse ve. rods

cone; outer surface of disks embedded in the cell membrane; faster
rods; disks are stacked inside of cell membrane; slower

15

rod vs. cone

slow vs fast
less light vs more light

16

recording of rod during stimulation of punctate sites with a llaser

no matter where a photon lands, the whole outer segment of rod hyperpolarizes

17

origin of receptor currents

when dark; depolarized; sodium influx
when light; hyperpolarized; sodium block

18

phototransduction cascade under dark and under light


lots of cGMP in cytoplasm keep open Na channels in outer membrane

1. opsin molecule (e.g. rhodopsion in rod, embeded in the disks) switches from 11-cis to all-trans (e.g. metarhodopsin)
2. in all-trans state opsin activates GTP-binding protein - transducin(its alpha subunit binds GTP and activates a phosphodiesterase;PDE)
3. phosphodiesterase (PDE) hydrolyzes cGMP to GMP
4. concentration of cGMP drops. many cGMP fall away from NA channal closing the channel, hyperpolarizing the cell

19

one photon absorbed by one molecule of opsin activates --- molecules of dransducin

800 molecules of transducin

20

each molecule of transducin activate ---- phosphodiesterase

1 phosphodiesterase (PDE)

21

each molecule of phosphodiesterase hydrolizes

upto 6 molecules of cGMP

22

how does one photon affect sodium channes and membrane potential?

one photon leads to the closure of 200 sodium channels and drop 1mV in membrane potential

23

adaptation

great sensitivity of phototransduction cascade ---> early saturation
adaptation extend the dynamic range of response
dependent on Ca (retinal Na Channel also permeable to Ca)
Na channel closure -> Ca decrease -> increased guanylate cyclase activity - increase more cGMP - and rhodopsin kinase activity - phosphorylated metarhodopsin binds arrestin interferes ability of metarhodopsin to activate transducin - (which are inhibited by Ca)

24

decrease in calcium concentration in Rod

increase guanylate cyclase => increase cGMP
increase rhodopsin kinase => phosphorylate metarhodopsin -> bind arrestin which conflicts with transducin

25

sensitivity of rods and cones

blue(cone) - rod - green (cone) - red (cone)

26

Ocular dominance

Perceive depth