Vision Flashcards
What physical aspect is the difference between the low-res and high-res eye?
The high-res has a focusing lens
What was the origin of the Opsin protein?
From a melatonin binding protein
What does opsin bind to in humans?
What does it form?
Binds to Retinal
Forms Rhodopsin
Where are the highest number of cones found?
In the fovea
What do rods detect?
What do cones detect?
Light or absence of light
Colour
What photopigment do rods use?
What photopigment do cones use?
Rods - Rhodopsin
Cones - Photoposins
Define scotopic and mesopic
Scotopic - nocturnal
Mesopic - works best at dusk or dawn
What is the first cell to start an action potential in the eye?
Ganglion cells
What cells receive input from photoreceptors?
Bipolar cells
Are the photoreceptors cis or trans-retinal in the presence of light?
Trans
List the process of phototransduction after light enters the cell
- Retinal is recycled
- Alpha GDP from transducin binds to opsin to form GTP
- GTP binds to PDE to activate it and cause AP
What is the membrane polarity in darkness?
In light activation?
Depolarized
Hyperpolarized
Is neurotransmitter release all or nothing?
No, they are graded based on amount of light
What does the receptive field contain?
All photoreceptors and bipolar cells feeding to one ganglion
What neurotransmitter is used in phototransduction?
Describe what cells secrete it when it is dark, or when it is light, and whether it is stimulatory or inhibitory
Glutamate
Cones or rods secrete inhibitory glutamate in dark
Bipolar cells secrete stimulatory glutamate when activated by light
