Physiology of Vision Flashcards

1
Q

List some important characteristics of rods

A

-high sensitivity, specialized for night vision
-high amplification because of higher density of rods to cones and more connections to bipolar cells
-achromatic: one pigment
-free-floating discs

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2
Q

List some important characteristics of cones

A

-low sensitivity, specialized for day vision
-less amplification
-chromatic: three types of pigment

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3
Q

What is the phototransduction process?

A
  1. light activated rhodopsin by converting tis 11-cis retinal to the all trans state
  2. this leads to formation of metarhodopsin II which triggers the next steps in the process
  3. the semi-stable intermediate form of rhodopsin then converts back to its original state
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4
Q

What is the dark current?

A

The resting photoreceptor potential that is slightly depolarized because of Na+ entry, occurs when its dark

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5
Q

how is receptor potential generated?

A

after light activates rhodopsin, the g-protein transducin is stimulated which in turn activates cGMP phosphodiesterase which decreases cGMP and closes the Na+ currents of the “dark current”

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6
Q

Describe the effects of on-center/off-surround

A

light excited (depolarizes) the center bipolar cell, increasing APs while inhibiting (hyperpolarizing) the surrounding bipolar cells, decreasing APs

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7
Q

Describe the effects of off-center/on-surround

A

Light inhibits (hyperpolarizes) the center bipolar cell, decreasing APs while light excites (depolarizes) the surrounding bipolar cells, increasing APs

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8
Q

Why are there different bipolar cell responses?

A

Opposite effects of the glutamate neurotransmitter on the postsynaptic membrane

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9
Q

What is the lateral geniculate nucleus?

A

It receives visual information from the retina and sends it to the primary visual cortex area of the cerebral cortex for processing

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10
Q

What are the receptive fields of the visual cortex?

A

Simple, complex and movement-sensitive complex cells

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11
Q

What are simple cells and what do they do?

A

They respond best to bars of light that have the correct position and orientation and represent the converging input from the round lateral geniculate receptive fields

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12
Q

what are complex cells and what do they do?

A

They are larger receptive fields that may depend on an edge of the field being illuminated and represent converging input from a group of simple cells having the same axis of orientation

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13
Q

perception of color depends on what?

A

simulation of at least two sets of photoreceptors

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14
Q

what are the color vision receptive fields?

A

green vs. red and blue vs. yellow (red+green)

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