Visual Processing Flashcards

1
Q

What are photoreceptors and where are they located?

A

Photoreceptors are light-sensitive neurons located in the retina.

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2
Q

What are the two main types of photoreceptors in the retina?

A

cones and rods.

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3
Q

How do photoreceptors respond to stimuli?

A

with graded membrane potentials instead of firing action potentials.

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4
Q

What is the structure of cones and rods?

A

Both cones and rods have outer segments with disk-like layers, inner segments, and a synapse

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5
Q

How does light affect photoreceptors?

A

When light hits photoreceptors, pigment molecules change shape, triggering a chemical cascade that hyperpolarizes the cell, reducing its release of glutamate.

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6
Q

What pigment is found in rods?

A

rhodopsin

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7
Q

What is the appearance of the fovea?

A

a central pit in the macula, densely packed with cones.

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8
Q

Where is the blindspot and why is it called a blindspot?

A

The blind spot occurs when the optic nerve exits the eye

there are no photoreceptors in this region.

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9
Q

What type of lighting conditions are cones mainly used in, why, and what is their job?

A

Cones are less sensitive and function in bright light, distinguishing colours.

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10
Q

How do rods adapt to darkness?

A

Rods rebuild their stores of rhodopsin over approximately 30 minutes in a process called dark adaptation.

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11
Q

How are cones and rods distributed in the retina?

A

Cones are concentrated in the fovea, while rods are mainly found in the peripheral retina, making peripheral vision more sensitive to light.

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12
Q

What is a receptive field in the visual system?

A

It refers to the set of photoreceptors influencing cell in the retina.

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13
Q

What is the difference between on-center and off-center bipolar cells?

A

On-center cells are excited by light in the center and inhibited by light in the surroundings, while off-center cells are the opposite.

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14
Q

How do bipolar cells respond to uniform lighting?

A

Bipolar cells do not respond to uniform lighting because the effects of the center and surroundings cancel out, reacting only to contrast.

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15
Q

What is the function of retinal ganglion cells? (3)

A

receive input from bipolar cells

detect contrast

transmit visual information via action potentials to the brain.

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16
Q

How is visual information compressed before reaching the brain?

A

The retina condenses input from 126 million photoreceptors into about 1 million ganglion cells

16
Q

Where is the optic chiasm located, and what happens there?

A

The optic chiasm is where optic nerve fibres cross, with nasal retina fibers crossing to the opposite side of the brain, while temporal fibers do not.

17
Q

what is the job of photoreceptors?

A

They convert light energy into electrical energy in cells through phototransduction.

18
Q

how many cones does the retina have?

A

6 million cones

19
Q

how many rods does the retina have?

A

120 million rods.

20
Q

what pigments are found in cones

A

cones have three different pigments corresponding to different types of cones.

21
Q

what is the job of the fovea and why?

A

It is used for detailed vision and has the highest visual acuity.

22
Q

What type of lighting conditions are rods mainly used in?

A

Rods are more sensitive, functioning in dim light but are bleached out in bright conditions.

23
Q

why is visual information compressed before reaching the brain?

A

reducing redundancy to transmit information efficiently.

24
Q

what does the outer layer contain in cone and rod structures?

A

visual pigments

25
Q

what does the inner layer contain in cone and rod structures?

A

nucleus and organelles

26
Q

what does the synapse in cones and rods release?

A

glutamate.