Physiology of Vision Flashcards
what’s the function of the iris
controls size of pupil
effects amount of light entering the eye
what’s the aqueous humor and what’s its function
transparent gel
anterior part of eye
maintains intraocular pressure (IOP)
what causes glaucoma
increased IOP
degeneration of trabecular meshwork
what’s the function of the trabecular meshwork
drain the aqueous humor
what’re the 3 layers of the posterior eye from inside out
- retina
- fovea
- sclera
how many layers are in the retina
10
what cells are in the retina (6)
.
P
M
B
H
G
rods & cones
pigment cells photoreceptor cells
muller cells
bipolar cells
horizontal cells
ganglion cells
what’s the difference between rods and cones
RODS
- no colour
- low light levels
- high sensitivity to light
- more photopigment
- slow response
cones
- colour
- daylight
- low sensitivity to light
- less photopigment
- fast response
where in the rods and cones are the photopigments held
membrane disks
what’s the function of bipolar cells
create pathway form photoreceptors -> ganglion cells
what the function of horizontal cells
feed information horizontally in ‘outer plexiform layer’
what’s the role of amacrine cells
control majority of inputs & responses to ganglion cells
what’s the role of muller cells
hold nerve cells in place (glial cell)
- ensheath all retinal neurones
how many opsins are there in rods
3 (green, red, blue)
what is the purpose and what’re the steps of the phototransducer pathway
(HINTS:
1.______ signals -> _____ signals in _____ & ______
2. photopigment proteins ____ & ____
3. ____ bind to _____
4. _____ hit this^
5. Triggers ______
- light -> electrical signals in rods & cones
- photopigment protein (opsin & rhodopsin)
- g-protein coupled receptor binds to vit. A
- light photons hit
- cascade within cell & visual process
describe the steps of ‘signal transducer in photoreceptors’
(HINTS
1. ____ activated
2. ______ exchanges ____ for ____
3.the currently activated ______, _______ and activates ____ & ___
4._____ hydrolyses ____ -> _____which causes decreased levels of _____ in ____
5. _______ close = membrane ________
6.____ released into ______
7. cascade
- rhodopsin activation
- GDP-bound-transducin -> exchange GDP for GTP
- GTP-bound-transducin, dissociates -> activates cGMP & PDE
- PDE hydrolyses cGMP -> 5’cGMP = decreased levels of cGMP in cytoplasm
- cGMP-gated ion channels close = membrane hyperpolorisation
- neurotransmitters released in photoreceptors
- cascade
what’re the 2 types of receptive fields
direct
indirect
what’s the direct receptive field
photoreceptors -> bipolar cells
what’s the indirect receptive field
photoreceptors -> horizontal cells -> bipolar cells
What’re the names of the 10 retinal layers from inside out
- Internal limiting membrane
- Muller cells
- basal lamina - Nerve fibre layer
- axon of ganglion cells - Ganglion cell layer
- ganglion cell bodies - Inner plexiform layer
- synapses between bipolar & ganglion cells
- actin site for amacrine cells - Inner nuclear layer
- nuclei & cell bodies of:
- bipolar
- muller
- amacrine - Outer plexiform layer
- synapses of:
- bipolar
- horizontal
- photoreceptor - Outer nuclear layer
- photoreceptor nuclei & cell body - External limiting membrane
- inner segment of photoreceptors
- apical process of muller cells - Photoreceptor layer
- rods & cones - Retinal pigment epithelium
- pigment cells
What’s the meaning of Dichromacy?
1/3 colour mechanism not functioning (green, red, blue)
What’s the meaning of Deuteranopia?
Mutation of green opsin (X-linked)
What’s the meaning of Protanopia?
Mutation of red opsin (x-linked)
What’s the meaning of Tritanopia ?
Mutation of blue opsin
