Photoreceptors Flashcards

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1
Q
A
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2
Q

Where are the rods and cones found?

A

the retina

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3
Q

What are rods?

A

cells which cannot distinguish between the different wavelengths of light and processes images in black and white

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4
Q

Why can rods detect light at very low intensities?

A

retinal convergence- many rod cells connect to one sensory neurone

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5
Q

what is the protein pigment found in rod cells?

A

rhodopsin

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6
Q

What does light cause to happen in the rod cells?

A

break down of rhodopsin

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7
Q

What cells link rod cells to the sensory neurone?

A

bipolar cells

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8
Q

Why can the threshold be met at low light intensities?

A
  • rhodopsin can be broken down at low light intensities
  • many rod cells are connected to one sensory neurone, so spatial summation occurs (collectively it is a big enough stimuli)
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9
Q

What is a disadvantage of retinal convergence?

A

less accurate vision at low intensities, as the brain cannot distinguish between the different light sources

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10
Q

What is meant by the term low visual acuity

A

two light sources close together cannot be seen as separate

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11
Q

What are the three iodopsin pigments found in the different type of cone cells?

A

red, green and blue

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12
Q

What is different about the 3 types of cone cells?

A

ca all absorb different wavelengths of light

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13
Q

What allows us to see colour images?

A

the varying proportions of light absorbed by cone cells

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14
Q

Why is a more light needed to stimulate a response in cone cells?

A
  • iodopsin is only broken down in high light intensities/requires more light energy to be broken down
  • no retinal convergence or spatial summation(one cone cell connected to one bipolar cell)
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15
Q

What is an advantage of not having retinal convergence in cone cells?

A

high visual acuity

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16
Q

Describe the distribution of rods and cones

A

uneven

17
Q

What is the fovea?

A

the point where the lens focuses most light, therefore the point receiving the highest light intensity

18
Q

Why are most cone cells located near the fovea?

A

as it is the area with the highest light intensity and cone cells require high light intensities to respond

19
Q

Why are rod cells further away from the fovea?

A

as they only need lower light intensities to respond

20
Q

What is the blind spot?

A

an area of the retina with no photoreceptors, so no light can be detected