Exam 2 Koh- Retina Biochem 3

Question 1

Tonic cells for _____, phasic cells for _______

Answer 1

Color, movement

Question 2

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

Answer 2

1-3%

Question 3

What are melanopsin ganglion cells for?

Answer 3

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

Question 4

How do ipRGCs respond to light?

Answer 4

Via the photopigement melanopsin

Question 5

Melanopsin shares more homology with what?

Answer 5

Invertebrate rhadomeric opsins

Question 6

Glutamate

Answer 6

Major excitatory transmitter of horizontal cells, ganglion cells

Question 7

GABA

Answer 7

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

Question 8

Glycine

Answer 8

Inhibitory neurotransmitter in amacrine cells

Question 9

Acetylcholine

Answer 9

Major excitatory transmitter of amacrine cells

Question 10

Dopamine occurs in ____ cells

Answer 10

Amacrine

Question 11

Taurine

Answer 11

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

Question 12

Photoreception ranges cover ___ orders of magnitude in intensity

Answer 12

~12

Question 13

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

Answer 13

2-3

Question 14

What is light adaptation?

Answer 14

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

Question 15

Bleaching of cone photopigment has a ______ effect on cone thresholds

Answer 15

Smaller

Question 16

Bleaching rhodopsin by 1% raises threshold by how much?

Answer 16

10 (decreases sensitivity by 10)

Question 17

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

Answer 17

Less

Question 18

Biochemical and neural feedback do what to the cone response?

Answer 18

Speed up

Question 19

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

Answer 19

Faster

Question 20

How big is the pupillary aperture?

Answer 20

1.5mm to 8mm

Question 21

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

Answer 21

30

Question 22

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

Answer 22

Decrease sensitivity

Question 23

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

Answer 23

Increase sensitivity

Question 24

What is the adaptation at the neural level of light?

Answer 24

Retinal neurons in all layers increase or decrease signal output

Question 25

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

Answer 25

500, 50

Question 26

Low calcium leads to what things?

Answer 26

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

Question 27

_____ adaption takes longer to achieve than ____ adaption

Answer 27

Dark, bright

Question 28

What happens in dark adaptation?

Answer 28

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

Question 29

What happens in bright adaptation?

Answer 29

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

Question 30

Why do pilots wear red goggles in strong light?

Answer 30

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

Question 31

What are Muller cells?

Answer 31

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

Question 32

What are astrocytes?

Answer 32

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

Question 33

What are microglias?

Answer 33

Can be stimulated into macrophagic function after trauma to retina

Question 34

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

Answer 34

Retina

Question 35

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

Answer 35

High, facilitatively

Question 36

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

Answer 36

Na/K ATPase actively

Question 37

______ is an insulin-independent tissue

Answer 37

Retina

Question 38

How does glucose enter the retina?

Answer 38

From choroid and retinal blood vessels

Question 39

Where are glucose transporters found?

Answer 39

RPE, retina, retinal blood vessels

Question 40

Where is glucose stored?

Answer 40

As glycogen in Muller cells and also in some retinal neurons

Question 41

What supplies the main source of ATP?

Answer 41

Glucose metabolism

Question 42

_____% of glucose is used in photoreceptors

Answer 42

>80

Question 43

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

Answer 43

ATP

Question 44

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

Answer 44

Inner

Question 45

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

Answer 45

75

Question 46

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

Answer 46

85

Question 47

Retina metbolizes majority of glucose ______ brain does it ______

Answer 47

Anerobically, aeorbically

Question 48

The retina can also use what 3 things for ATP?

Answer 48

Glutamate, malate, and succinate

Question 49

Retinal lipids are made up of mainly what?

Answer 49

Phospholipids

Question 50

What are the 2 predominant retinal lipids?

Answer 50

Phosphatidylcholine and phosphotidylethanolamine

Question 51

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

Answer 51

Oxidative

Question 52

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

Answer 52

PE (phosphotidylethanolamine), cholesterol