control > L33 - visual defects > Flashcards

L33 - visual defects Flashcards

(59 cards)

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1
Q

vitreous humour

A

viscous jellylike substance that lies between the lens and the retina

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2
Q

conversion of light into neural activity

A
  • light is focused by the conea, then the lens, then passes through the vitreous humour to the retina
  • retina lies in front of the pigment epithelium which absorbs any light not absorbed by the retina
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3
Q

pigment epithelium

A

filled with black pigment melanin which absorb any light not absorbed by the retina
- stops light bouncing inside the eye, improving resolution

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4
Q

what do bipolar neurones release

A

glutamate

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5
Q

phototransduction

A

conversion of light energy into electrical energy

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6
Q

where in cones does phototransduction occur

A

invaginated membrane

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7
Q

where in rods does phototransduction occur

A

membranous discs

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8
Q

photoreceptors in the dark

A

depolarised

continuously release glutamate

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9
Q

photoreceptors in the light

A
  • depolarised ion channels close
  • photons are absorbed
  • membrane is hyperpolarised
  • glutamate release reduced
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10
Q

photopigments

A

individual transmembrane proteins

G-protein coupled receptors

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11
Q

retinal

A
  • embedded within photopigments

- synthesised from vitamin A

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12
Q

what happens when retinal is hit with a photon if light

A

it undergoes a conformational change, activating Rhodopsin molecule

  • G-protein coupled amplification
  • activates transuding and phosphodiesterase
  • breakdown of cyclic GMP
  • when levels fall, ion channels are closed
  • hyperpolarisation
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13
Q

resolution when denser photoreceptors

A

better

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14
Q

on bipolar cells in light

A

depolarise

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15
Q

off bipolar cells in light

A

hyperpolarise

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16
Q

mechanism of off bipolar cells

A
  • glutamate receptors
  • Na can permeate through and depolarise the cell
  • when light comes along, glutamate decreases and unbinds
  • ion channels close
  • hyperpolarisation occurs
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17
Q

mechanism of on bipolar cells

A
  • glutamate activates G-protein coupled receptor, inhibiting an ion channel
  • when light comes along, glutamate decreases, preventing inhibiting of the ion channel
  • depolarisation
  • releasing inhibition
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18
Q

off bipolar cells as light gets dimmer

A

depolarises

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19
Q

on bipolar cells as light gets dimmer

A

hyperpolarises

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20
Q

receptive field

A

the area of the retina that causes any change in response of a neurone

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21
Q

outer retina receptive field

A

horizontal cells shape receptive fields of bipolar cells

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22
Q

inner retina receptive field

A

amacrine cells shape receptive fields of ganglion cells

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23
Q

lateral inhibition

A

regions of retina which are outside the lateral extent of the dendrites of the ganglion cells
- form inhibitory synapses with ganglion cells

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24
Q

In dim light, the presence of which molecules causes ion channels in rod cells to open?

Study These Flashcards
A

cGMP molecules

25
The 3 types of cone cells can detect which 3 colours (each cone has 1 of 3 opsins)?
blue green red
26
What happens to the size of photoreceptors further away from the fovea?
Photoreceptors further from the fovea are larger in size
27
What is the name of the pigment in all rod cells called?
Rhodopsin
28
What are the 2 colour opponent pathways?
red/green | blue ON/yellow OFF
29
opsin
receptor protein of rhodopsin
30
what colour do we see when all cone cells are equally active
white
31
what type of firing if just red hits the centre of the receptive field
maximum firing
32
firing if green surrounds and red is in the centre
green inhibits the excitation of red in the centre
33
What are ipRGCs (intrinsically photosensitive retinal ganglion cells) required for?
pupillary light reflex | they connect the Edinger-Westphal nuclei
34
striate cortex
primary visual cortex
35
melanospin
5th photopigment | expressed by retinal ganglion cells
36
where is melanopsin expressed
intrinsically photosensitive retinal ganglion cells
37
groups of layers of the LGN
parvocellular magnocellular koniocellular
38
layers 3-6 of the LGN
parvocellular (small cell bodies)
39
layers 1-2 of LGN
magnocellular layers (large cell bodies)
40
What is the name of the small layers between layers 1-6 in the LGN?
Koniocellular layers
41
What do magnocellular cells receive input from?
M-type ganglion cells
42
Magnocellular cells
- large receptive field - important for detection of stimulus movement - 5% population
43
parvocellular cells
- smaller cell type | - 90% populations
44
What do koniocellular cells receive input from?
K-type
45
What do parvocellular cells receive input from?
P-type
46
koniocellular cells
- medium cell type | - 5% population
47
ganglion cells
M ganglion cells P ganglion cell K ganglion cell
48
M ganglion cell
Large fields allow them to be responsive to motion as they can compare the visual fields the whole time
49
P ganglion cell
- Provides more high resolution information - Only receiving input from bipolar cells connected to photoreceptors - Concerned with working out what the stimulus is
50
K ganglion cells
works out which direction someone is coming towards you / object motion sensitive
51
What can be said about all neurons in the vertical column?
They display the same orientation specificity
52
what can be said about neighbouring columns
similar orientation but slightly shifted in angle
53
What is an orientation column?
A column of the cortex of neurones that are all connected to each other and are selective to the same orientation of a stimulus
54
Neurones in oblique rows display what kind of orientation specificity?
heterogenous
55
what are blobs
- pillars of neurones in the primary visual cortex - rich with cytochrome oxidase - where colour-processing occurs
56
Information from the primary visual cortex is transmitted to which lobe for processing of visual motion?
parietal lobe
57
Information from the primary visual cortex is transmitted to which lobe for recognition of objects?
temporal
58
What is the part of the brain that is involved in working out where objects are relative to ourselves?
Superior colliculus
59
cytochrome oxidase
mitochondrial enzyme - cell metabolism
control
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