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biology - 18 - response to stimuli > The Eye > Flashcards

The Eye Flashcards

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1
Q

What are the light receptors in the eye

A

Rods and cones

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2
Q

Why are the rides and cones also transducers

A

They convert light energy into the electrical energy of a nerve impulse

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3
Q

What are light sensitive pigments

A

They breakdown when exposed to certain intensities or wavelengths of light

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4
Q

Where do pigments breakdown

A

Photoreceptors

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5
Q

What does the breakdown of pigment in the photoreceptors trigger

A

Generator potential in bipolar neurones they synapse with

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6
Q

What do bipolar neurones synapse with

A

Sensory neurones in the optic nerve which directly connect with the brain

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7
Q

What photosensitive pigment do rod cells contain

A

Rhodopsin

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8
Q

What does rhodopsin detect and in what light intensity

A

Detect light at very low light intensity

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9
Q

How do rod cells cross the threshold value to reduce a generator potential

A
  • low light intensity has enough energy to breakdown rhodopsin
  • retinal convergence occurs
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10
Q

What is retinal convergence

A

A number of rods are connected to 1 bipolar neurone which gives a greater chance of crossing the threshold in the bipolar neurone and creating a generator potential

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11
Q

Why must a the threshold value be crossed

A

To make sure generator potential occurs leading to a action potential being transmitted to bipolar neurone and impulse goes to the brain

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12
Q

Explain why rod cells don’t see colour

A

Cannot distinguish differences between wavelengths of light therefore images appear in back and white

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13
Q

What type of intensity to cone cells respond to

A

High light intensity

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14
Q

What photosensitive pigment do cone cells contain

A

Iodopsin

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15
Q

Why do cone cells only respond to high light institute

A

Iodopsin in cone clls is only broken down at high light intensity
They are each connected to a single bipolar neurone so stimulation of a number of cone cells can’t be combined to exceed the threshold value = low retinal convegance

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16
Q

How do cone cells allows us to see colour

A
  • 3 different type of cone each witch different type of Iodopsin
  • each type of Iodopsin is sensitive to a specific range of wave lengths
  • depending on proportion of each type of stimulation we see imagines in full images
17
Q

What is trichromatic theory

A
  • depends on colour mixing of the primary colour green red and blue
  • Proposes there are 3 types of of cone sensitive to three wavelengths, if one of these types is stimulated on its own we will see that colour
18
Q

What is colour seen also determined by

A

Excitation of the 3 receptors

19
Q

Red

A

Cone sensitive to red

20
Q

Green

A

Cone sensitive to green

21
Q

Blue

A

Cone sensitive to blue

22
Q

Yellow

A

Cone sensitive to red and green

23
Q

Cyan

A

Cone sensitive to green and blue light

24
Q

Magenta/purple

A

Cone sensitive to blue and red light

25
Q

White

A

Cone sensitive to red blue and green light

26
Q

What is visual acuity

A

The ability for the eye to resolve 2 or more stimuli separated spatially

27
Q

Are cones or rods responsible for visual acuity

A

Cones

28
Q

Why do rod cells give low visual acuity

A
  • objects cannot be distinguished as separate due to low visual acuity
  • connected to same bipolar neurone = high density
  • light received fro rod cells sharing same cell only generate a singe impulse regardless of number of rods that are stimulated
29
Q

High visual acuity

A
  • Objects can be distinguished as separate due to high visual acuity
    Connected to separate bipolar neurones - low sensitivity
30
Q

What part of retina are cones situated

A

The fovea

31
Q

Rod connection

A
  • high retinal conveyance
  • greater chance threshold value is reached at low light intensity = high sensitivity
  • low visual acuity
32
Q

Cone connection

A
  • low retinal convergence
  • Smaller chance of threshold value will be reached at low light intensity = low sensitivity
  • high visual acuity
33
Q

Importance of fovea

A

Enables accurate vision in bight light and colour vision

34
Q

What allows us to detect objects in ver low light

A

Retinal convergnace - many rods synapse to a single neurone

35
Q

What allows us to distinguish between points very close together

A

Visual acuity - one cone synapses to a singe neurone

biology - 18 - response to stimuli (7 decks)

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