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Physiology semester 2 > The eye Ch. 51 > Flashcards

The eye Ch. 51 Flashcards

receptor and neural function of the retina

1
Q

Light path to retina

A

lens – vitreous humor –>retina (bounces off pigmented layer in retina)

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2
Q

How many layers does the retina have?

A

9 (light pathway begins with pigmented layer)

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3
Q

At central foveal region, inside layers

A

are NOT present to increase visual acuity

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4
Q

Rods are useful in the

A

dark

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5
Q

cones are useful in the

A

light

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6
Q

Components of rods and cones (4)

A
  1. outer segment
  2. inner segment
  3. nucleus
  4. synaptic body
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7
Q

Inner segment of cones and rods have

A

mitochondria (ATP needed to activate enzymes)

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8
Q

Types of cones (3)

A
  1. Red
  2. Blue
  3. Green
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9
Q

Light sensitive chemical is located on

A

outer segment

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10
Q

Outer segment contains

A

1000 discs

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11
Q

Color pigments are located

A

on outer segment in disc membranes

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12
Q

Inner segments contain

A

Organelles, cytoplasm, many mitochondria

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13
Q

Synaptic body role

A

connects with neuronal cells: horizontal and bipolar cells

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14
Q

Melanin role

A

Prevents light reflection through eyeball = enhances contrast for formation of precise image

albinism = bad vision

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15
Q

Vitamin A is a precursor for

A

rhodopsin

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16
Q

Retinal blood supply

A

central retinal artery via optic nerve

highly vascular tissue between retina and sclera

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17
Q

Retinal detachment

A

retina detaches from pigment epithelium = fluid and blood collect between layers

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18
Q

Rhodopsin location

A

outer segment of rod

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19
Q

Once light energy is absorbed, what happens (photochemistry)

A

Rhodopsin begins to rapidly decompose due to photoactivation of electrons = changes from cis to trans form

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20
Q

Photochemistry of vision

A

Revisit slide 5 and ninja nerd special senses video
https://www.youtube.com/watch?v=GKaFjw8N8zQ

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21
Q

Vitamin A

A

precursor with isomerase to convert all-trans retinal to 11-cis retinold

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22
Q

Low vitamin A levels can cause

A

night blindness

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23
Q

Rod excitation is

A

Hyperpolarizing

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24
Q

What causes hyperpolarization of rods?

A

Rhodopsin decomposes and membrane conduction decreases for sodium ions

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25
Q

Sodium flows into rods in the

A

dark

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26
Q

Sodium flows through ___ in rods

A

cGMP-gated channels

27
Q

In the light, what happens to sodium flow in rods?

A

cGMP channels close, stopping flow of sodium into rod

28
Q

What rodopsin is activated cGMP channels are

A

closed

29
Q

activated rodopsin stimulates

A

G-protein transducin

30
Q

transducin

A

activates cGMP phosphodiesterase

31
Q

cGMP phosphodiesterase breaks down

A

cGMP to 5’-cGMP. Reduced cGMP closes channels (-70mV)

32
Q

In the dark, sodium flows through cGMP gated channels and causes membrane potential to be

A

-40 mV

33
Q

Rod excitation cascade

A
  1. photon (light) activates electron in 11-cis retinol –> metarhodopsin II
  2. activated rhodopsin enzymatic function –>activates transducin
    3.activates phosphodiesterase
    4.hydrolyzes cGMP –>sodium channels close
    5.Rhodopsin kinase –>inactivates metharhodopsin and cascade reverses (including opening sodium channels)
34
Q

Cones are more/less sensitive than rods

A

30-300 times less sensitive

35
Q

cones use ___ for activation

A

photopsins

36
Q

Long exposure to light leads to

A

retinal and opsins

37
Q

retinal is converted to

A

Vitamin A

38
Q

Long exposure to darkness results in (2)

A
  1. retinal and opsin conversion to light-sensitive pigments
  2. Vitamin A converted to light sensitive pigments
39
Q

Cones adapt after

A

a few minutes

40
Q

Rods adapt for

A

minutes to hours and show extreme sensitivity

41
Q

Mechanisms of light and dark adaptation beyond rod/cone adaptation (2)

A
  1. pupil size
  2. neuronal adaptation
42
Q

Color vision

A

Blue, green and red cones each absorb separate certain % of light nm

Brain interprets these absorptions as color

43
Q

Red-green colorblindness occurs when

A

red or green cones are missing, X - linked

44
Q

Photoreptors are

A

rods and cones

45
Q

Rods and cones synapse on

A

horiztonal and bipolar cells

46
Q

Bipolar cells transmit signals

A

vertically

47
Q

Bipolar cells synapse on

A

Amnicrine and ganglion cells

48
Q

Amnicrine cells synapse on

A
  1. bipolar to ganglion
  2. horiztonally to inner plexiform from axons of bipolar cells
49
Q

Ganglion cells role

A

sent signals from retina to optic nerve of brain

50
Q

Foveal vision pathway

A

cones –>bipolar cells –>ganglion cells

51
Q

Peripheral retina pathway

A

rods –>bipolar cells –>amacrine cels –> ganglion cells

52
Q

Rods and cones release _____

A

glutamate when synapsing with bipolar cells

53
Q

amarcrine cells secreute

A

Inhibitory nuerotransmitters (usually)

GABA, glycine, dopamine, acetylcholine, indolamine

54
Q

all retinal neurons except _____ transmit via_____

A

except ganglion cells transmit via electronic conduction

55
Q

Electronic conduction is

A

graded conduction of signal strength

56
Q

Output from horizontal cells is always

A

inhibitory

lateral inhibition = stops the spread

57
Q

Lateral inhibition creates

A

contrast borders in image

58
Q

Amacrine cells respond to (2)

A
  1. Change in illumination
  2. movement of a spot - directionally sensitive
59
Q

How many rods converge on an optic nerve fiber?

A

Up to 200 = summation

60
Q

P ganglion cells

A

slower impulse, stimuli sustained, sensitive to color

NOT sensitive to low contrast (not great in dark)

“new” brain

61
Q

M ganglion cells

A

Large, faster impulse, not sensitive to color (black and white stimuli)

“reptile”. brain

62
Q

Ganglion cells receive signal from

A

bipolar cells (could be excitatory or inhibitory)

63
Q

How is color contrast created?

A

One ganglion can be stimulated by several or only a few cones

some ganglion cells are excited by one type and inhibited by a second type

64
Q
A

Physiology semester 2 (7 decks)

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