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visual science1 > Retinal Mechanism photoreceptors I > Flashcards

Retinal Mechanism photoreceptors I Flashcards

1
Q

How many rods and cones does the retina contain

A

120 million rods , 6 million cones

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2
Q

Where are visual pigments made

A

In the Inner segment

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3
Q

Where are visual pigments stored

A

In the outer segment

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4
Q

What does each visual pigment molecule consist of

A

A protein (opsin) and a retinal (aldehyde of vitamin a)

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5
Q

What is opsin

A

The structure that determines which wavelength of light they absorb

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6
Q

What is retinal

A

Portion that captures light photons

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7
Q

How many photo/visual pigments does the retina have

A

Four

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8
Q

How many visual pigments does every photo receptor have

A

Only 1 of the 4 types

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9
Q

What is the visual pigment that all rods have

A

Rhodopsin

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10
Q

What visual pigment does cone have

A

Each cone has 1 of 3 pigments; (L-cones/erythrolabe) responds to long wavelength, ( m-cones/chlorolabe) respond to medium wvl, and (s-cones/cynolabe) responds to short wvl

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11
Q

How are visual responses initiated

A

When an absorbed photon causes a change in the shape of chromophore molecule from cis to trans

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12
Q

What is the change from cis to trans called

A

Photoisomerisation

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13
Q

What is the pigment molecule that all mammalian have as their chromophore

A

11-cis retinal

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14
Q

The chance of photon being absorbed by a receptor depends on what

A

Frequency and spectral sensitivity of photoreceptor

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15
Q

How many photons can a person detect

A

100 photons

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16
Q

What happens to the photons detected

A

1/2 of photons bounce off cornea -> 50 photons reach retina -> only 7 visual pigments molecules are isomerized

17
Q

What happens to absorbed photons

A

Only 2/3 of photons absorbed by photoreceptors actually result in a response

18
Q

Where is the only place that the rod pathway neutrons doesn’t the cone system

A

Central fovea

19
Q

Why is there a high degree of convergence in peripheral vision

A

To ensure high sensitivity

visual science1 (1 decks)

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