The Eye (II) Flashcards
What allows interaction between outputs in retina
Horizontal and amacrine cells
True or false. Many rods can converge to a single bipolar cell to increase light sensitivity
True
True or false. It is only 1 bipolar cell which attaches to ganglion cell
False. Many bipolar cells can converge
Where do AP first appear
Ganglion cell (rest is graded potentials)
Are bipolar cells always excited by glutamate (in dark)
No, some are inhibited by glutamate release in dark so are active in light
What does a ganglion cell receptive field mean
Area of retina which excites the ganglion cell
What is the receptive field of ganglion cells called
Centre surround organisation
Explain centre surround organisation
Two types of ganglion cell
On centre/off surround
Off centre/on surround
What does on centre off surround mean
Excitation via light on the centre of ganglion causes AP
Inhibition due to light on the surround, responds to dark more
Why is the AP weak of light is shone to ganglion cell whole of it
Because it excites one but inhibits the other
Contrast is better where dark is at the inhibitory site and light at excitatory
What process allows edges to be defined at ganglion cells
Lateral inhibition
Which organisation do cone ganglion cells have and what are the 2 types
Centre surround organisation
Red(long wavelength) - green (medium wavelength) : one excites one inhibits
Blue (short wavelength) - yellow (mix of long and medium green and red)
What would happen if white light with red and green wavelengths was shone onto cone red green ganglion cell
Weak excitation
Red would stimulate but green would inhibit
Where does info cross over from the optic fibre
Optic chiasm
Which fibres cross over in chiasm
One from each nasal retina
Where do fibres from right eye go from chiasm
Right lateral geniculate body (thalamus)
Where does info go from right lateral geniculate body for the left eye go
Left visual cortex
Where is the visual cortex
Occipital lobe
Which receptive field do neurones in lateral geniculate body have
Centre surround organisation
How are neurones at visual cortex more specific for stimulation/ receptive field
Prefer bars not dots
Need to be in correct position for stimulus
Need to be in right orientation for stimulus
Do neurones in visual cortex prefer moving objects
Yes
What are the neurones for specific position or orientation calls
Position - simple
Orientation - complex
What are the 2 pathways info goes down in visual cortex
Dorsal stream - action pathway
Ventral stream - recognition pathway
What does dorsal stream action pathway do
Decide how to act on stimulus / light
What does ventral recognition pathway do
Detect edges and shape to identify object
