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LS 2 Final > Final: Sensory Systems: Eyes Slides > Flashcards

Final: Sensory Systems: Eyes Slides Flashcards

1
Q

What is the stimulus for eyes?

A

Light (have light-sensitive photoreceptors, that have pigment that senses light)

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2
Q

What are the layers of the eye (outer to inner)?

A

Fibrous, vascular, neural

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3
Q

What does each layer of the eye do (general)?

A

Fibrous: outer layer that provides protection with its fibers
Vascular: middle layer; where blood vessels are (provide nourishment)
Neural: inner layer; convert light info to electrical activity

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4
Q

Parts of fibrous layer

A

Cornea and sclera

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5
Q

Sclera function

A

Muscle attachment; allows precise movement of eyeballs without needing to move whole head

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6
Q

Sclera structure and location

A

Majority of outer layer; white part of eye

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7
Q

Cornea structure and location

A

On top of colored part of eye; thick, transparent membrane; convex

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8
Q

Cornea functions

A

Protection but more importantly, corrects vision: convex shape corrects for distortion caused by movement of light through different medias (air then liquid)

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9
Q

Parts of vascular layer (6)

A

Ciliary muscles (smooth), iris, pupil, zonular fibers, lens, choroid

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10
Q

Choroid structure and function

A

Dark, pigmented layer to concentrate light (contains blood vessels)

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11
Q

Zonular fiber function

A

Hold lens in place

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12
Q

Ciliary muscle function

A

Accommodation: allows objects to be focused on retina no matter how near or distant they are (perfect camera that immediately adjusts) - changes shape of lens

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13
Q

Pupil function

A

Opening for light to enter (covered by cornea)

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14
Q

What type of muscles are ciliary muscles?

A

Involuntary smooth muscle

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15
Q

When is the lens in each shape?

A

Flattened (ciliary muscles relax, zonular fibers tight): object is far
Rounded (ciliary muscles contract, zonular fibers loose): object is near

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16
Q

What is the iris?

A

Colored part of the eye, with pupil at center

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17
Q

How/when does pupil size change?

A

Dim light: radial smooth muscles contract, pupil dilates

Bright light: circular smooth muscles contract, pupil constricts (smaller)

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18
Q

What happens in the neural layer?

A

Transduction: light converted to electrical activity, which is sent to the brain (neurons are here)

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19
Q

Retina function

A

Contains photoreceptors to receive light and send it to brain through optic nerve

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20
Q

Where is the highest density of photoreceptors?

A

Fovea centralis (high visual acuity)

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21
Q

Types of cells in retina (5)

A

Ganglion cells, amacrine, bipolar, horizontal, photoreceptors (rods and cones)

22
Q

Ganglion cell function

A

Send signal to brain to be interpreted

23
Q

Amacrine cell function

A

Support synapses between bipolar and ganglion cells

24
Q

Horizontal cell function

A

Support/strengthen synapses between photoreceptors and bipolar cells

25
Q

What’s the formula for sensation?

A

Need a receptor cell to synapse with neuron

26
Q

Pathway after light hits photoreceptors (rods/cones)

A

Rods and cones form connections with bipolar cells/neurons - bipolar cells form connections with ganglion cells - ganglion cells send signal to brain

27
Q

Difference between rods and cones

A

Rods: see B&W, more sensitive (extremely sensitive) to light, respond to low illumination
Cones: see more details (color), less sensitive to light (need a lot of light for stimulation), respond to high illumination

28
Q

What do photoreceptors need to absorb light?

A

Pigment

29
Q

Pigment-containing protein in rods

A

Rhodopsin (starts process of electrical activity)

30
Q

Pigment-containing protein in cones

A

Photopsin

31
Q

Which pigment do the proteins in rods and cones contain?

A

Retinal

32
Q

Types of pigments in cones

A

Small (blue), medium (green), large (red) - size refers to wavelength

33
Q

When are cones and rods depolarized?

A

When we CAN’T see (counter-intuitive)

34
Q

When are cones and rods hyperpolarized?

A

When we CAN see

35
Q

Cones/rods in the dark

A

high cGMP levels - Na+ channels open - Na+ influx causes depolarization - Ca2+ channels open - Ca2+ influx - NT (glutamate) release - graded potential in bipolar cells

36
Q

What do Na+ channels in photoreceptors respond to?

A

Chemically gated; respond to cGMP (open with cGMP is high, closed when it’s low)

37
Q

How does light induce chemical change in rods (start signal pathway)?

A

Retinal (pigment) changes chemical conformation - rhodopsin changes shape - activates transducin - alpha subunit translocates and activates phosphodiesterase - breaks down cGMP - Na+ channels close - hyperpolarization - no receptor potential, no NT release, no bipolar cell activity - brain IS getting signal

38
Q

What is transducin?

A

Very similar to G protein - has three subunits; alpha subunit translocates and activates phosphodiesterase in photoreceptors

39
Q

Rods/cones when exposed to light

A

low cGMP levels - Na+ channels closed - hyperpolarization - no NT release - no graded potential - nothing happens in bipolar cells - brain receives signal

40
Q

Visual field

A

When you fixate on one point, what you can see without moving your head

41
Q

Central vision

A

What you can see clearly in the visual field (in front of you)

42
Q

Peripheral vision

A

Outer edges of vision; things still visible but no longer clear

43
Q

Why is central vision clear?

A

Binocular vision: seeing things with both eyes visual fields overlap

44
Q

Where in the thalamus do visual signals go?

A

Lateral geniculate nucleus

45
Q

General neural pathway of vision

A

Nasal/temporal retina - optic nerve - optic chiasm - optic tract - lateral geniculate nucleus - visual cortex

46
Q

Which side of brain do nasal retina signals (from both R and L) go to?

A

Left side

47
Q

Which side of brain do temporal retina signals (from both R and L) go to?

A

Right side

48
Q

Macular degeneration

A

Lose central vision, but not peripheral vision

49
Q

Two optic nerves meet to form ____ _____

A

Optic chiasm

50
Q

What forms optic tracts?

A

Some axons cross to opposite side of brain

LS 2 Final (10 decks)

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