CH 5 Sensation & Perception (QUESTIONS) Flashcards
How far can light travel in a second?
300,000 km/s
What determines the characteristics of light waves?
The speed it travels
What range of light is visible? (1,4)
380 to 760 nm (billionths of a meter)
- 400 nm = Violet
- 500 nm = Green
- 600 nm = Yellow
- 700 nm = Red
How many rods are in the eye?
125 million
How many cones are in the eye?
6.4 million
What are the receptors of vision?
Rods and Cones
What makes up the optic nerve?
Ganglion cells
Are photoreceptors equally distributed across the retina?
No, the density of cones and rods depends on the region of the eye
___________ contains only cones. What does this explain?
- Fovea
- The fovea gives you the sharpest vision, but it’s useless in dim light because cones don’t work well in the dark.
20° from the centre (in periphery), the ________ has a maximum density of ___________ cells. What does this explain?
- Retina
- Rod
- This explains why your peripheral vision works better in low light but lacks colour and detail.
How do the pigments in rods and cones differ?
- Rods: Contains Rhodopsin = Retinal + Scotopsin
- Cones: Contains Iodopspin = Retinal + Photopsin
How does transduction occur?
Transduction of light into neural energy occurs through absorption of photons
How many photons of light are able to produce a visual response
7
Processes of transduction
- When photons hit the photoreceptors, the retinal part of the pigment changes shape (isomerizes) and splits into components (bleached: splits into retinal and opsin)
- The bleached pigment can’t detect light until it’s regenerated by reattaching the retinal and opsin.
When is pigment regeneration most effective?
In the dark
What happens in the dark?
Visual sensitivity (to light) increases over time in the dark as the rods and cones adjust
What does the Dark Adaptation Curve represent?
The break in the curve occurs when the rods become more sensitive than the cones
Process of the discontinuous function during dark adaptation (2,1)
- Initial sensitivity due to fast cone adaptation (7-10 minutes)
- Later sensitivity due to slower rod adaptation (10-30 minutes)
- Related to pigment regeneration
