Vision Flashcards
What are the pre-neural elements of the eye?
Cornea, lens and ocular media
All focus and filter the light before reaching the retina
What is light energy converted into ?
electrical signals
What does the retina do?
mediates the conversion of light energy to electrical signals
Describe the characteristics of Rods
- low spatial resolution
- high sensitivity ( 1 photon)
- dominant at night
- loss of function = night blindness
- less dense
- membrane disks unattached to outer mem
Describe the characteristics of cones
- high spatial resolution
- low sensitivity
- less saturation
- rapid recovery
- colour vision, dominant at daylight
loss of cone = blind - dense
- membrane disks attached to outer mem
What is the first stage in central processing of vision?
5 layers of retina
What are the five layers of the retina ?
- Photoreceptors
- Bipolar cells
- ganglion cells
- Amacrine cells
- Horizontal cells
What is the optic nerve made of ?
retinal ganglion cell axon
What happens at the optic chasm ?
partial crossing of optical nerves so the temporal fields cross
What information does the pretectal nucleus get?
reflexive eye movements
What information does the suprachismatic nucleus get?
sleep-wake cycle
What does peripheral vision mean ?
detected by one eye
What provides refraction in the eye?
cornea
What is accommodation in terms of vision?
changing ur optical power to focus near + far by relaxing and contracting
What do oposins do in phototransduction ?
Sit within the mem of disc
Sensitive to particular waves
How are signals terminated ?
calcium ion decrease as channels close
cGMP restored
Rhodopsin kinase gets activated and phosphorylated causing transducin displacement
How many logs of light intensity are there?
12
How do we see in colour?
Colour vision = trichromatic 3 cones all are monochromatic Blue - short Green - medium Red - long comparison of cones to extract colour info
What cells detect changes in luminance?
Ganglion cells
What are the classes of ganglion cells ?
on-centre (light in receptive field = AP)
off-centre (light turned off = AP)
Equal numbers of both
What NT do ganglion cells use?
glutamate
