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Bio 8: Grey Matter > The Eye > Flashcards

The Eye Flashcards

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Biology 101 flashcards
1
Q

List the structure of the eye we need to know

A
  • The pupil
  • The lens
  • Iris
  • Blind spot
  • Fovea
  • Retina
  • Optic nerve
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2
Q

What is the function of the pupil in the eye?

A

Where light enters the eye

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3
Q

What is the function of the iris in the eye?

A

Controls how much light enters the eye

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4
Q

What is the function of the fovea in the eye?

A

Area of retina containing many photoreceptor cells - mostly cones

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5
Q

What is the function of the retina in the eye?

A

Full of photoreceptor cells to detect light

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6
Q

What is the optic nerve?

A

Bundle of nerves that carries nerve impulses from the retina to the brain

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7
Q

What is the blind spot?

A
  • Area of the eye with the retina photoreceptors

- Where optic nerve leaves eye

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8
Q

Label an eye diagram

A

See notes

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9
Q

How do the photoreceptors in eye conduct impulses to the brain? 6

A
  • Light is focused onto retina by lens
  • Absorbed by pigments in the photoreceptors
  • Causes some sodium ion channels to open
  • If threshold is reached an action potential is generated
  • Carried through bipolar neurone to optic nerve
  • Takes impulses to the brain
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10
Q

What are the 2 types of photoreceptor?

A
  • Rods

- Cones

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11
Q

List the properties of the rod cells 4

A
  • Monochromatic [one pigment: black/white]
  • Low visual acuity
  • More sensitive to low light
  • 3 rods to one bipolar neurone
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12
Q

Where are rod cells mostly found?

A

Peripheral part of retina

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13
Q

Where are cone cells mostly found?

A

Concentrated in the fovea

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14
Q

List the properties of cone cells 4

A
  • High visual acuity
  • Trichromatic [three pigments]
  • 1 cone to each bipolar neurone
  • Less sensitive to low light
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15
Q

What optical pigments do cone cells detect?

A
  • Red pigment
  • Green pigment
  • Blue pigment
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16
Q

How are different colours seen?

A

Different proportions of optical pigments are stimulated

17
Q

How do pupils react to low light? 5

A
  • Photoreceptor detects low light
  • Transmits impulses along sensory neurone to CNS
  • CNS via relay neurone to radial muscles in iris
  • Radial muscles contract
  • Pupils dilate
18
Q

How do pupils react to bright light? 5

A
  • Photoreceptor detects bright light
  • Transmits impulses along sensory neurone to CNS
  • CNS via relay neurone to circular muscles in iris
  • Circular muscles contract
  • Pupils contract
19
Q

How is pupil dilation/contraction an example of a reflex?

A
  • It’s fast

- It’s unconsciously done

20
Q

Explain what happens to rod cells in the dark. 13

A
  • Steady flow of Na+ ions into outer segment
  • Through open cation channels
  • Through the cell surface membrane
  • At the same time CSM actively pumps Na+ out of cell
  • Active transport needs ATP from mitochondria in inner segment
  • Concentration gradient maintained between inner and outer segment
  • Na+ ions flow down
  • Depolarises cell slightly
  • Potential difference across is -40mV
  • Cell releases glutamate neurotransmitter across synapse
  • Binds to bipolar cell and stops depolarisation
  • Stops cation channels in bipolar cell opening so no Na+ enters
  • No action potential generated in optic nerve synapsing with bipolar cell
21
Q

Explain what happens to rod cells in the light 12

A
  • Light on the retina causes rhodopsin to break down by bleaching
  • Into trans-retinal and opsin
  • Opsin catalyses a series of membrane bound reactions
  • Closing the cation channels in the outer segment
  • Influx of Na+ ions blocked
  • Inner segment actively pumps out Na+
  • Interior of cell is more negative causing hyperpolarisation
  • Neurotransmitter glutamate not released across synapse
  • Depolarisation occurs in bipolar cell
  • Because cation channels are still open
  • Action potential generated in optic nerve
  • Transmitted to visual cortex of the brain
22
Q

What must occur for the rod cell to be restimulated in the light?

A

Rhodopsin must be reformed

23
Q

How is rhodopsin reformed? 3

A
  • ATP from the mitochondria in the inner segment
  • Converts trans-retinal back into cis-retinal
  • Rejoins to opsin and rhodopsin is reformed

Bio 8: Grey Matter (11 decks)

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