Dark adaptation of light

[scilearner]

Hello everyone,

 

What is dark adaptation of light? Is it the adaptation of rods and cones, when you are exposed to bright light for some time, and then move to a dark area. I know some chanes that occur.

 

1.the retinal and opsins in the rods and cones are converted back into the light-sensitive pigments

2. Pupils dilate- Why is that? I know light of more intensity enters, but if light sensitive pigments are not generated, how could this be beneficial.

3. The other mechanism is neural adaptation, involving the neurons in the successive stages of the visual chain in the retina itself and in the brain. What exactly is this neural adaptation.

 

Also what is the textbook saying in this paragraph.

 

Value of Light and Dark Adaptation in Vision. Between the limits of maximal dark adaptation and maximal light adaptation, the eye can change its sensitivity to light as much as 500,000 to 1 million times, the sensitivity automatically adjusting to changes in illumination.

Because registration of images by the retina requires detection of both dark and light spots in the image, it is essential that the sensitivity of the retina always be adjusted so that the receptors respond to the lighter areas but not to the darker areas. An example of maladjustment of retinal adaptation occurs when a person leaves a movie theater and enters the bright sunlight. Then, even the dark spots in the images seem exceedingly bright, and as a consequence, the entire visual image is bleached, having little contrast among its different parts. This is poor vision, and it remains poor until the retina has adapted sufficiently so that the darker areas of the image no longer stimulate the receptors excessively.

Conversely, when a person first enters darkness, the sensitivity of the retina is usually so slight that even the light spots in the image cannot excite the retina. After dark adaptation, the light spots begin to register. As an example of the extremes of light and dark adaptation, the intensity of sunlight is about 10 billion times that of starlight, yet the eye can function both in bright sunlight after light adaptation and in starlight after dark adaptation.

 

Thanks

[hypervalent_iodine]

Hello everyone,

 

What is dark adaptation of light? Is it the adaptation of rods and cones, when you are exposed to bright light for some time, and then move to a dark area. I know some chanes that occur.

 

1.the retinal and opsins in the rods and cones are converted back into the light-sensitive pigments

2. Pupils dilate- Why is that? I know light of more intensity enters, but if light sensitive pigments are not generated, how could this be beneficial.

3. The other mechanism is neural adaptation, involving the neurons in the successive stages of the visual chain in the retina itself and in the brain. What exactly is this neural adaptation.

 

Also what is the textbook saying in this paragraph.

 

 

 

Thanks

 

 

 

From memory, a lot of it has to do with phosphorylation and dephosphorylation of one of the proteins in your retina in response to light (or a lack there-of). I'm afraid it's been a while since I've done this, so I don't know much more than that without looking it up.