Week 9 - Vision Flashcards
(27 cards)
What is light?
Electromagnetic radiation measured in nanometers (nm); visible range is 380–760 nm.
What happens to light when it hits an object?
It can be reflected, absorbed, or refracted.
How does light enter the eye?
Through the cornea → pupil → lens → vitreous humour → retina.
What is the function of the lens?
Focuses light onto the retina by changing shape (accommodation).
What are the types of retinal neurons?
Photoreceptors, bipolar cells, ganglion cells, horizontal and amacrine cells.
What is the function of rods?
Located in periphery; sensitive to light; monochromatic; low acuity.
What are cones
Located in fovea; less sensitive; detect hue; high acuity.
What is transduction in vision?
Conversion of light to neural signals via photoreceptors.
What happens when light hits a photoreceptor?
It hyperpolarises and reduces glutamate release.
What happens in darkness?
Photoreceptors depolarise and increase glutamate release.
What is a receptive field?
Visual area that influences neuron firing.
How does receptive field size affect vision?
Small = high acuity, low sensitivity; large = low acuity, high sensitivity.
Where are parvocellular ganglion cells found?
In the fovea, small receptive fields, high acuity.
Where are magnocellular ganglion cells found?
In the periphery, large receptive fields, low acuity.
What is the retinofugal pathway?
Route from retina to visual cortex.
What happens at the optic chiasm?
Nasal axons cross; lateral axons remain on same side.
What visual field does each LGN receive?
Contralateral visual field.
What are magnocellular layers responsible for?
Movement, depth, form, light-dark contrast.
What are parvocellular layers responsible for?
Colour (red/green) and fine detail.
What are koniocellular layers responsible for?
Colour processing (blue-yellow).
What is V1?
Primary visual cortex (striate cortex), with six layers.
What is the extrastriate cortex?
Regions V2–V8; involved in higher-order processing.
What are the two visual streams?
Dorsal (‘where’ – motion/location) and ventral (‘what’ – object identity).
What is trichromatic coding?
Three cone types: red (long), green (medium), blue (short wavelengths).
