11 Light Sensitivity & Spatial Resolution Flashcards
Why do we have two photoreceptors?
Our species lives on a planet that has day and night
Slide 1
If more than one photons was needed to activate one receptor they would have to be ________
synchronous
Slide 2
For a rod that needed two photons to respond, light intensity has to increase
102,000
Slide 2
Chances of two photons captured by the same rod at the same time ( within 100 ms) ?
once every 16 years
Slide 2
Dim light is _____
NOISY. We can very reliably distinguish objects from one from the other.
Slide 3
Objects (at day and night) are seen against a _______ background
Noisy
Slide 4
What stops noisy background noise?
All the physiology we have talked about (horizontal cells, etc)
Slide 4
Rods are _____ but they are _______
noisy, reliable
Slide 5
Why are rods so noisy?
They fire spontaneously, even when they do not have a photon to activate them
Slide 5
Rods fire spontaneously every _____ minute(s).
2
Slide 5
what does “eigengrau” mean?
Spontaneous activity (in German)
Slide 5
In the picture in Slide 5 there are 3 colors. What does each mean?
Black =
Red =
Green =
Photon catch on rod of:
black = star red = sky green = eigengrau, rod pretends to catch photon
Slide 5
***Picture in slide 6, important concept.
Rods will _________
saturate
Slide 6
Rods will capture to 1, 2, 3 photons and _____ their amplitude of response.
At some point rods will _______ and stop increasing the amplitude of response.
increase, saturate
The rod cannot keep increasing their respond because what if 100 photons hit it? No….
Slide 6
If rods saturate, what does this mean for day light?
They are at their max response rate
Dynamic range of rods is ____ log units?
6
Summing responses of photons in rods is ___ log units?
2
A single rod can pick up a single photon within ___ seconds
30
In what conditions do rods do their best?
Dim light
Rods help detect slight gradations in what color?
Black/Grey
True/False: Rod bipolar cells receive the response from a single photon from a single rod (or from upwards of 200 photons from 10-15 different rods) and scales it before relaying the signal
True
Cones can respond to ________ photons/s catch rate
1,000000
Cones respond in ____ms and sum responses above rate of ____photons/s
50, 20
