5.8 Flashcards

1
Q

Retina contains light-sensitive cells:

A

rods and cones

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2
Q

Rods and cones are

A

receptor cells

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3
Q

a receptor cell is able to

A

detect changes in the environment and converts sensory information into a form that can be transmitted to the CNS

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4
Q

The light has to travel through several layers of neurones to reach the

A

light-sensitive rods and cones

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5
Q

Underneath the rods and cones is a layer of cells containing the pigment, melanin which

A

absorbs any light that is not absorbed by the rods and cones

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6
Q

(Rods) outer segment contains many vesicles of the light-sensitive pigment

A

rhodopsin

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7
Q

when light hits a rod cell it causes the rhodopsin to

A

split into opsin and retinal

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8
Q

(rods) when rhodopsin splits it is a process known as

A

bleaching

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9
Q

Bleaching results in the permeability of the rod cell to sodium ions to be

A

altered

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10
Q

Rod cells set up a

A

generator potential

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11
Q

(ROD GP) if this is enough to overcome the threshold value, an AP is generated in the sensory neurone which carries the impulse along the

A

optic nerve to the brain

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12
Q

after, the rhodopsin is regenerated, which requires energy from

A

ATP

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13
Q

Rod cells are extremely sensitive to low light intensities, so they are most useful for

A

vision in dim light

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14
Q

rod cells cannot distinguish between different wavelengths, so they produce black and white images only, known as

A

monochromatic vision

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15
Q

several rods synapse with just one sensory neurone - means that rod cells have

A

low visual acuity

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16
Q

Grouping of rod cells together also increases their sensitivity known as

17
Q

if each of the several rod cells results in a tiny amount of neurotransmitter being released into the synaptic cleft, these small amounts ‘add together’ so that there is enough to set up an

A

action potential in the sensory neurone

18
Q

there are many more rod cells in the retina than

19
Q

rods are found evenly spread across the retina, although there are very few at the

20
Q

cones are similar in structure to rods, but contain a pigment of

21
Q

(Cones) 3 different kinds of iodopsin each sensitive to

A

red, green or blue light

22
Q

(cones) different colours are perceived depending on the

A

proportion of the different types of cone that are stimulated

23
Q

(CONES) e.g. if red and green cones are stimulated equally, the brain interprets the colour as yellow. this is called the

A

trichromatic theory of colour vision

24
Q

cone cells are not as sensitive to light as rods, so they only work in

A

high light intensity

25
there are fewer cones than rods in the
retina
26
most of these cone cells are concentrated at the
fovea
27
the fovea is the part of the retina where the centre of the image is focused when you
look straight at an object
28
most cones have an individual connection to a sensory neurone, meaning that
cones have much greater visual acuity than rods