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neural circuits > visual system > Flashcards

visual system Flashcards

1
Q

main function of retina

A

Main function of the retina is image acquisition

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2
Q

Lateral Geniculate nucleus function

A

Lateral Geniculate nucleus preprocess the visual information

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3
Q

where does most processing of info occur

A

visual cortex

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4
Q

Two main cortical visual pathways

A
  • ventral = object identification
    • inferior temporal
  • dorsal = object localisation
    • posterior parietal
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5
Q

Pupil function

A

regulates the amount of light that falls on the retina

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6
Q

Lens function

A

focuses image on the fovea

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7
Q

Fovea function

A

a part of the retina with highest visual acuity

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8
Q

distribution of rods and cones

A

more cones at fovea, more rods at periphery of retina

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9
Q

structure of retina

A

pigment epithelium
photoreceptors
horizontal cells
bipolar cells
amacrine cells
ganglion cells -> optic nerve

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10
Q

neurotransmitter released by bipolar cells

A

glutamate

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11
Q

Feedforward neurons

A

photoreceptors, bipolar cells and ganglion cells

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12
Q

Feedback neurons

A

horizontal cells and amacrine cells

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13
Q

outer plexiform layer

A

synapses between photoreceptors, bipolar cells and horizontal cells

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14
Q

inner plexiform layer

A

synapses between bipolar, amacrine and ganglion cells

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15
Q

rod and cone response to light intensity

A

Rods are active at dim light and cones are active at bright

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16
Q

where does phototransduction occur

A

outer segment of retina

17
Q

how do photoreceptors respond to light flashes

A

hyperpolarisation (decrease in membrane potential)

18
Q

phototransduction cascade

A
  • LIGHT = cGMP → GMP
  • GMP → cGMP by phospodiesterase
  • LIGHT = decreased glut
  • DARK = increased glut
    cGMP activates ion channels of membrane of photoreceptors
19
Q

glutamate release in photoreceptors

A

Constant release of glutamate in darkness
Less glutamate is released during activation by light

20
Q

laminar retinal organisation

A
  • Bipolar and horizontal cells receive input from photoreceptors in the outer plexiform layer (OPL)
  • Ganglion cells and amacrine cells receive input from bipolar cells (and ganglion cells from amacrine cells) in the inner plexiform layer (IPL)
21
Q

ON cells response to light

A

ON cells depolarise when light intensity

22
Q

OFF cells response to light

A

hyperpolarise in response to light

23
Q

On bipolar cell activation

A
  • Use mGluR instead of AMPAR
  • G-protein (Go), not the same as in photoreceptor cascade
  • Removal of cGMP is not required for ion channel closure
24
Q

proteins with role in on cell regulation

A

TRPM1: expressed in ON but not OFF cells
Nyctalopin, proteoglycan required for light and glutamate responses in ON cells

25
Q

on and off cell stratification in layers

A
  • OFF = project closest layer to bipolar cells
  • ON = project closest layer to ganglion cells
    Axons of ON bipolar cells and dendrites of ON ganglion and amacrine cells are located in the same sublaminae in the IPL
26
Q

Receptive field

A

= area in the retina (or space) which when illuminated activates a visual neuron

27
Q

centre surround organisation

A

= organisation of bipolar(and gaglion) cells
- illumination of the center and the surround leads to responses in opposite polarities
- Some activate directly (centre) while others activate via horizontal cells(surround) and therefore cause the cell to depolarise

28
Q

classes of ganglion cells

A
  • parvocellular
  • magnocellular
29
Q

parvocellular ganglion cells

A
  • are tuned to process information about shape and colour
  • sustained response
30
Q

magnocellular ganglion cells

A
  • process information about motion
  • fast responses
  • transient response
31
Q

morphology of ganglion cells dendritic trees

A

Morphology of ganglion cells differs in the size of the dendritic trees, some are assymetric, some are sparse and so on. Do not try to memorise each type. Just appreciate the diversity.
- E.G asymmetric dendritic trees
- useful directionality of motion

32
Q

What is response adaptations and sensitivity

A
  • Adaptation: decrease in activity (spiking rate)
  • Sensitisation: increase in activity

neural circuits (12 decks)

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