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neuro > The visual system: eye and retina > Flashcards

The visual system: eye and retina Flashcards

1
Q

How much of the neocortex is involved in analysing the visual world?

A

1/3

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2
Q

What colour do short wavelengths in visible light appear?

A

Blue

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3
Q

What is the wavelength?

A

Distance between peaks and throughs

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4
Q

What is the frequency?

A

Number of waves per second

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5
Q

What is the amplitude?

A

The difference between a wave peak and a trough

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6
Q

What are optics?

A

Light interacting with the environment

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7
Q

Why does refraction occur?

A

The speed of light differs between mediums

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8
Q

Function of the pupil

A

Lets light inside the eye

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9
Q

Function of the iris

A

Contains muscles which control the amount of light entering the eye

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10
Q

Function of the cornea

A

Glassy transparent covering of the pupil and iris
-Refracts light and focuses towards the back of the eye
- Nerve endings which adapt over time

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11
Q

Function of the sclera

A

Forms the tough, protective wall of the eyeball to give it shape

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12
Q

Function of the extraocular muscles

A

Move the eyeball
Controlled by oculomotor nerve (cranial nerve 3)

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13
Q

Function of the optic nerve

A

Carries axons from the retina to the brain
- Cranial nerve 3

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14
Q

What type of animal has horizontal pupils?

A

Prey animals
- For wider vision

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15
Q

What is the optic disk?

A

Origin of blood vessels and the optic nerve
- Cannot sense light

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16
Q

What is the macula?

A

Region of the retina for central vision
- Devoid of large blood vessels to improve vision quality

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17
Q

What is the fovea?

A

Thinnest section of the retina
- Area of highest visual acuity

18
Q

How does stretching of the lens occur?

A

Lens is suspended by zonal fibres (suspensory ligaments), attached to ciliary muscle, enabling stretching

19
Q

What is the degree of refraction determined by?

A

Difference in refractive indices between the two media
The angle at which light hits the interface between the two media

20
Q

Describe refraction by the cornea

A

Cornea is mainly water
- Light travels more slowly through water than air due to higher density so refraction occurs

21
Q

What is the focal distance?

A

Distance from refractive surface to convergence of parallel light rays

22
Q

What happens to the lens when objects are <7m away?

A

The lens fattens to provide additional refraction

23
Q

What is emmetropia?

A

Eye is in a normal state and can focus on the back of the retina

24
Q

What is hypertropia?

A

Eyeball is too short so near objects are focussed behind the retina due to lack of refraction

25
Q

How is hypertropia fixed?

A

With convex glasses

26
Q

What is myopia?

A

Eyeball is too long so near objects are focused before the retina

27
Q

How is myopia fixed?

A

Concave glasses

28
Q

What cells does light pass through before it reaches photoreceptors?

A

Ganglion and bipolar cells

29
Q

What are plexiform layers?

A

Regions where synaptic connections occur

30
Q

Function of a ganglion cell in the retina

A

Output from the retina
- Produce action potentials

31
Q

Function of an amacrine cell

A

Modulates information transfer between ganglion and bipolar cells

32
Q

Function of bipolar cells in the retina

A

Connect photoreceptors to ganglion cells

33
Q

Function of horizontal cells

A

Modulate information transfer between photoreceptors and bipolar cells

34
Q

Function of a photoreceptor in the retina

A

Sensory transducers
- Both rods and cones

35
Q

Describe the structure of a photoreceptor

A

Membranous disks that contain light-sensitive photopigments that absorb light

36
Q

Function of a rod

A

High sensitivity
- Enable vision in low light

37
Q

Function of a cone

A

High resolution
-Colour
- Daylight photopic

38
Q

Structure of a rod

A

Greater number of disks than a cone
Higher photopigment conc
100x more light sensitive than cones

39
Q

Structure of a cone

A

Fewer disks than rods

40
Q

Describe convergence, sensitivity and resolution in the central retina

A

Low convergence
Low sensitivity
High resolution

41
Q

Describe convergence, resolution and sensitivity in the peripheral retina

A

High convergence
High sensitivity
Low resolution

42
Q

What changes the polarity of bipolar cells ?

A

Glutamate release at the synapse

neuro (25 decks)

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