Exam 2 Koh- Retina Biochem 3 Flashcards Preview

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

Flashcards in Exam 2 Koh- Retina Biochem 3 Deck (52):
1

Tonic cells for _____, phasic cells for _______

Color, movement

2

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

1-3%

3

What are melanopsin ganglion cells for?

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

4

How do ipRGCs respond to light?

Via the photopigement melanopsin

5

Melanopsin shares more homology with what?

Invertebrate rhadomeric opsins

6

Glutamate

Major excitatory transmitter of horizontal cells, ganglion cells

7

GABA

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

8

Glycine

Inhibitory neurotransmitter in amacrine cells

9

Acetylcholine

Major excitatory transmitter of amacrine cells

10

Dopamine occurs in ____ cells

Amacrine

11

Taurine

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

12

Photoreception ranges cover ___ orders of magnitude in intensity

~12

13

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

2-3

14

What is light adaptation?

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

15

Bleaching of cone photopigment has a ______ effect on cone thresholds

Smaller

16

Bleaching rhodopsin by 1% raises threshold by how much?

10 (decreases sensitivity by 10)

17

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

Less

18

Biochemical and neural feedback do what to the cone response?

Speed up

19

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

Faster

20

How big is the pupillary aperture?

1.5mm to 8mm

21

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

30

22

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

Decrease sensitivity

23

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

Increase sensitivity

24

What is the adaptation at the neural level of light?

Retinal neurons in all layers increase or decrease signal output

25

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

500, 50

26

Low calcium leads to what things?

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

_____ adaption takes longer to achieve than ____ adaption

Dark, bright

28

What happens in dark adaptation?

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

29

What happens in bright adaptation?

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

Why do pilots wear red goggles in strong light?

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

What are Muller cells?

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

32

What are astrocytes?

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

33

What are microglias?

Can be stimulated into macrophagic function after trauma to retina

34

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

Retina

35

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

High, facilitatively

36

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

Na/K ATPase actively

37

______ is an insulin-independent tissue

Retina

38

How does glucose enter the retina?

From choroid and retinal blood vessels

39

Where are glucose transporters found?

RPE, retina, retinal blood vessels

40

Where is glucose stored?

As glycogen in Muller cells and also in some retinal neurons

41

What supplies the main source of ATP?

Glucose metabolism

42

_____% of glucose is used in photoreceptors

>80

43

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

ATP

44

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

Inner

45

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

75

46

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

85

47

Retina metbolizes majority of glucose ______ brain does it ______

Anerobically, aeorbically

48

The retina can also use what 3 things for ATP?

Glutamate, malate, and succinate

49

Retinal lipids are made up of mainly what?

Phospholipids

50

What are the 2 predominant retinal lipids?

Phosphatidylcholine and phosphotidylethanolamine

51

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

Oxidative

52

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

PE (phosphotidylethanolamine), cholesterol