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Dark Adaptation

Describe what happens in the retina (at the cellular level) when you "get used to the dark. Why is it not possible to see color at night?

This question involves neurotransmitters and channels. Text for course is "from neuron to brain" if you have access.

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Let's start by examining the mechanism of light detection in the eye. The retina is composed of cones and rods. The cones are focused at the center of the fovea at the back of the eye and are responsible for color sensitivity. The rods are more spread out and are responsible for light level detection. They are responsible for night vision. See for a good illustration and description.

Rods are incredibly sensitive to light and can detect as little as one quantum of light. Our rods can adjust to detecting light on the intensity of a moonless, cloudy night. This sensitivity allows us to see at night. Within the rods are photopigments ...