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Brain and behavior I > Chapter 4: Visual System > Flashcards

Chapter 4: Visual System Flashcards

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The Brain flashcards
1
Q

What is the function of the conjunctive?

A

Membrane that covers the front of the eye

Lines the inside of the eyelids

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2
Q

What is the function of the cornea?

A

Takes nutrients and fluid from the aqueous humour

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3
Q

What is the function of the pupil?

A

Opening that lets light enter the eye and reach the retina

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4
Q

What is the function of the iris?

A

Muscle that gives the eye its color and contraction lets eye adapt to changing light

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5
Q

What is the function of the lens?

A

Focuses light rays onto retina

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6
Q

What is the function of the retina?

A

Converts image formed by light rays into nerve impulses by photoreceptors

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7
Q

What bends light?

A

Aqueous and viteous humor

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8
Q

What do rods do?

A

Let you see shades of grey in low light conditions

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9
Q

What do cones do?

A

Sensitive to color in bright light conditions

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10
Q

What are the 3 categories of the opsins?

A

Blue cones
Red cones
Green cones

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11
Q

What is color blindness?

A

Lesions in part of the visual cortex

Cones containing opsins for seeing red-green absent

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12
Q

In what gene is the color blindness on?

A

x chromosome

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13
Q

What are the forms classified from for color blindness and what are they?

A

From the type of cone affected
Protanopia
Deuteranopia
Tritanopia

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14
Q

What is achromatopsy?

A

Total color blindness

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15
Q

What are the 3 layers of the retina?

A
  1. Photoreceptive layer
  2. Bipolar cell layer
  3. Ganglion cell layer
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16
Q

Describe layer 1 of the retina.

A
  • back of eye

- contains cones and rods

17
Q

Describe layer 2 of the retina.

A

conveys information from photoreceptors to ganglion cells

18
Q

Describe layer 3 of the retina.

A

Receives visual information from bipolar cells and axons give rise to optic nerve

19
Q

What is the dark current? And what is the membrane potential of the outer segment of rods in the dark?

A
  • When the retina is not stimulated, the photoreceptors continuously flow sodium
  • Approx. -30 mV
20
Q

What is the result of dark current?

A

Light hyperpolarizes photoreceptor cells and causes it to release fewer neurotransmitter molecules into synapse with bipolar cells

21
Q

Where is the fovea located and it’s the function?

A
  • region of retina
  • color-sensitive cones only in the fovea
  • acute vision of birds and higher mammals
22
Q

What is the optic disk’s location and function?

A
  • location of exit point from retina of fibers of ganglion cells
  • responsible for blind spot
23
Q

What is the path of the optic nerve?

A
  1. intersection of optic nerve of eyes at optic chiasm
  2. majority of optic tract projects to lateral geniculate nucleus
  3. projection from LGN to visual cortex via optic radiation
24
Q

What is the LGN?

A
  • 6 layers
  • receives input from only 1 eye (approx. 80%)
  • Layer 1-4-6: receive input from contralateral eye
  • Layer 2-3-5: receive input from ipsilateral eye
25
Q

what is the receptive field?

A

Portion of visual field where presence of a visual stimulus will modify the activity of a neuron in a layer of retina or cortex

26
Q

Describe what happens in presence and absence of light for bipolar cells.

A

Exposure of retina to light: hyperpolarizes rods and cones

Absence of light: neurons that connect rods and cones to ganglion cells actively inhibited by rods and cones

27
Q

What do the ganglion cells do?

A

Respond by increasing or decreasing the frequency with which they discharge action potentials

28
Q

What do complex cells do?

A

detect movement

29
Q

What do hyper-complex cells do?

A

See object’s edges and angles

30
Q

What is the role of the visual cortex (V1)?

A

Sends a large proportion of its connections to V2 and some directly to V5

31
Q

What does the ventral pathway allow and where does it entend to?

A
  • Temporal lobe
  • Allows to consciously perceive, recognize and identify objects by processing their intrinsic visual properties (shape and color)
32
Q

What does the dorsal pathway allow and where does it project to?

A
  • Parietal lobe

- Visual-motor control over objects by processing their extrinsic properties (size, position and orientation in space)

33
Q

What are the ventral (what) stream disorders?

A
  1. cerebral achromatopsia: complete or partial loss of color vision
  2. visual object agnosia: failure to recognize objects by the visual modality alone
  3. Pure Alexia:
    severe - can’t read words, numbers, letters, map signs or symbols
    mild - read abnormally slowly
  4. prosopagnosia: face blindness
34
Q

What are the dorsal (where) stream disorders?

A
  1. Akinetopsia: motion blindness
  2. Simultanagnosia: inability to sustain attention across different locations in visual field
  3. Contralateral neglect
  4. Blindsight

Brain and behavior I (6 decks)

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