(NAS Colloquium) Vision From Photon to Perception (1999) / Chapter Skim
Currently Skimming:
How photons start vision
How photons start vision
Pages 4-9
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 4... ...
The hyperpolarization relays visual information to the synaptic terminal, where it slows ongoing transmitter release. The cationic channels in the outer segment are controlled by the diffusible cytoplasmic ligand cGMP, which binds to channels in darkness to hold them open.
|
From page 5... ...
Dark Noise in Rods and Cones Dark noise sets the ultimate limit on the performance of many devices that count photons, and retinal rods are no exception. The electrical noise of rods contains two dominant components that may be confused with photon responses: (a)
|
From page 6... ...
In amphibian rods the noise has a magnitude and power spectrum consistent with a superposition of shot effects like those generated by absorption of photons, and it has been proposed that the noise arises from photoexcited rhodopsin which, during the shutoff process, escapes quenching and returns to the active state (19, 20~. In primate rods noise after bright light results partly from anomalous photon responses, which have a rectangular waveform (see below)
|
From page 7... ...
In one, the recombinant protein, kindly provided by Lubert Stryer, is being dialyzed into salamander rod outer segments. Leon Lagnado, Martha Erickson, and I have found that myristoylated (14-0)
|
From page 8... ...
Indeed, the single photon responses that arise in truncated rhodopsin molecules shut off after exponentially distributed delays with a mean of S s (Fig.
|
From page 9... ...
A light-triggered reduction in the activity of the glutamate receptor allows cGMP levels to rise, opening cationic channels in the surface membrane and producing a depolarization which carries the message onward. It will undoubtedly be satisfying to learn more about how synaptic transmission is "designed" to work in concert with the visual transduction mechanism.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.