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Anatomy and Biochemisty > Exam 2 Koh- Retina Biochem 3 > Flashcards

Exam 2 Koh- Retina Biochem 3 Flashcards

1
Q

Tonic cells for _____, phasic cells for _______

A

Color, movement

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2
Q

What percentage of intrinsically photosensitive retinal ganglion cells are retinal ganglion cells?

A

1-3%

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3
Q

What are melanopsin ganglion cells for?

A

Unconscious visual reflexes: pupillary constriction, daily behavioral and physiological rhythms (circadian rhythms)

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4
Q

How do ipRGCs respond to light?

A

Via the photopigement melanopsin

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5
Q

Melanopsin shares more homology with what?

A

Invertebrate rhadomeric opsins

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6
Q

Glutamate

A

Major excitatory transmitter of horizontal cells, ganglion cells

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7
Q

GABA

A

Functions particularly in the horizontal and amacrine cells as an inhibitory mediator

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8
Q

Glycine

A

Inhibitory neurotransmitter in amacrine cells

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9
Q

Acetylcholine

A

Major excitatory transmitter of amacrine cells

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10
Q

Dopamine occurs in ____ cells

A

Amacrine

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11
Q

Taurine

A

An amino acid closely related to Gaba and glycine, (ox bile), has unclear function, but cone degeneration is seen in cat without taurine in diet

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12
Q

Photoreception ranges cover ___ orders of magnitude in intensity

A

~12

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13
Q

At any given level of adaptation we can only discriminate within an intensity range of _____ orders of magnitude

A

2-3

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14
Q

What is light adaptation?

A

The process by which a photoreceptor exposed to a constant background light bright enough to saturate the receptor, regains the ability to respond incrementally to brighter light stimuli

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15
Q

Bleaching of cone photopigment has a ______ effect on cone thresholds

A

Smaller

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16
Q

Bleaching rhodopsin by 1% raises threshold by how much?

A

10 (decreases sensitivity by 10)

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17
Q

High levels of illumination bleach away photopigments making the outer segment ____ sensitive to light

A

Less

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18
Q

Biochemical and neural feedback do what to the cone response?

A

Speed up

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19
Q

The life span of activated cone opsin, its turn off, and the turn off of cone transducin are _____ than they are in rods

A

Faster

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20
Q

How big is the pupillary aperture?

A

1.5mm to 8mm

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21
Q

A ____ fold change of quantity of light entering the eye response in seconds

A

30

22
Q

What are the chemical processes in the photoreceptors for bright light?

A

Decrease sensitivity

23
Q

What are the chemical processes in the photoreceptors for dim light?

A

Increase sensitivity

24
Q

What is the adaptation at the neural level of light?

A

Retinal neurons in all layers increase or decrease signal output

25
Q

In the photoreceptor outer segment, free intracellular Ca2+ can fall from ___ nM in dark-adapted rods to ____ nM on illumination

A

500, 50

26
Q

Low calcium leads to what things?

A

1) activation of rhodopsin kinase phosphorylates of Rh+ 2) activation of guanylate cyclase activating proteins 3) increase in affinity of cation channel proteins for cGMP

27
Q

_____ adaption takes longer to achieve than ____ adaption

A

Dark, bright

28
Q

What happens in dark adaptation?

A

Rhodopsin are bleached and desensitized, cones are not stimulated, low intensity, takes about 20 min

29
Q

What happens in bright adaptation?

A

Cones are bleached at first, then adapt to a higher threshold, about 5 min, meta II of cone pigments forms faster than that of rhodopsin, meta II decays ~10-50x faster than that of rhodopsins, clearance of Ca2+ from cone outer segments is several times faster than rods

30
Q

Why do pilots wear red goggles in strong light?

A

Rods are insensitive to red but sensitive to other colors, if you wear a red filter then you help protect many of the rods from bleaching. If you go to a dim environment, you can take off the red filter and the rods will be ready to adapt to the dark environment

31
Q

What are Muller cells?

A

Rid waste, phagocytosis, neuroprotection, GABA, DA, taurine, glycogen, retinoic acid synthesis, ion homeostasis

32
Q

What are astrocytes?

A

Supportive role to the retinal ganglion cells, supports NFL, myelinating nerve fiber, covers BVs that feed the NFL, can store glycogen, ion homeostasis

33
Q

What are microglias?

A

Can be stimulated into macrophagic function after trauma to retina

34
Q

Blood flows to the ______ is relatively high in relation to other tissues

A

Retina

35
Q

The retina has a ____ metabolic rate; glucose is _____ transported

A

High, facilitatively

36
Q

Millions of ATP molecules is used per second by rods to run ________ actively

A

Na/K ATPase actively

37
Q

______ is an insulin-independent tissue

A

Retina

38
Q

How does glucose enter the retina?

A

From choroid and retinal blood vessels

39
Q

Where are glucose transporters found?

A

RPE, retina, retinal blood vessels

40
Q

Where is glucose stored?

A

As glycogen in Muller cells and also in some retinal neurons

41
Q

What supplies the main source of ATP?

A

Glucose metabolism

42
Q

_____% of glucose is used in photoreceptors

A

> 80

43
Q

Glucose is mainly used for _____ rather than fat or protein degradation

A

ATP

44
Q

Aerobic yield is 36 ATP per glucose and is confined to the _____ segment

A

Inner

45
Q

The isolated retina can produce ____% of its normal ATP production by glycolysis in the absence of oxygen

A

75

46
Q

In hypoglycemic conditions (1 mM glucose) it generates ___% of its normal ATP needs by oxidative metabolism

A

85

47
Q

Retina metbolizes majority of glucose ______ brain does it ______

A

Anerobically, aeorbically

48
Q

The retina can also use what 3 things for ATP?

A

Glutamate, malate, and succinate

49
Q

Retinal lipids are made up of mainly what?

A

Phospholipids

50
Q

What are the 2 predominant retinal lipids?

A

Phosphatidylcholine and phosphotidylethanolamine

51
Q

High content of polyunsaturated fatty acids in the outer segment are susceptible to ______ damage

A

Oxidative

52
Q

Disc membranes of photoreceptors are made of ____, while plasma membrane are comprised of _____

A

PE (phosphotidylethanolamine), cholesterol

Anatomy and Biochemisty (15 decks)

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