Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physiology > Retina > Flashcards

Retina Flashcards

1
Q

What are retinal pigments formed from?

A

Opsin - cell specific apoprotein long chain of amino acids

Chromophore derived from vitamin A

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the rod pigment?

A

Rhodopsin

Absorption spectrum of the dark adapted retina (peak at 500nm)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the inner segment of photoreceptors made up of? Function?

A

Ellipsoid - energy production (mitochondria are elipse)

Hyoid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Cones vs rods

A

Opsins in cones differ so that photopigments have maximal sensitivity to red blue or green light

Cone opsins differents from rhodopsin but similar structure

Red and green opsins have high homocology, blur opsin different

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What happens to outer segments each morning

A

Shedding of apical sections of photoreceptor outer segments

In rods maximal 1h after light exposure
Cones 2-3h after darkness

RPE cells phagocytose outer segments followed by digestion by lysosomal acid hydrolases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Differences between rods and cones

A

Cones 25-100 times less sensitive to single photon

Cones catch fewer photons

Cones have faster kinetics

Cones have grater ability to adapt to background light

Cones do not saturate at normal environmental light levels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens after phototransduction by photoreceptors

A

Motion and contrast information coded at ganglion cell level in rates of action potential.

Graded hyperpolarisation of photoreceptor is converted to phasic ganglion cell activity via various configuration of horizontal and bipolar cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What neurotransmitter to photoreceptors and bipolar cells use?

A

Glutamate

  • Glutamate is continuously released by photoreceptors and OFF bipolar cells

Activation by light stimuli decreases glutamate in the synaptic cleft

This is controlled by calcium concentration - increase in Ca2+ causes exocytosis whereas decrease results in more endocytosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What NT do horizontal and amacrine cells yse?

A

GABA or glycine - inhibtory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Initial step of glucose metabolism?

A

Glycolysis (no oxygen required)
Glucose -> pyruvate + 2 ATP + 2 NADH

Pyruvate enters TCA cycle which requires oxygen
- 36 molecules of ATP for each glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What pathway is active in rod outer segments for rhodopsin regeneration and protection from oxidative damage

A

Pentose phosphate pathway

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How does glucose enter the retina?

A

Throught RPE and retinal blood vessels

Facilitated diffusion through the RPE lying over fenestrated vessels of the choroid and endothelial cells of retinal vessels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How can glucose be stored in the retina?

A

Stored as glycogen in Muller glial cells and some retinal neurones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the processes of rod phototransduction?

A

Rhodopsin phosphorylation
Transducin GTPase
cGMP synthesis
ABCR retinal transport
Na extrusion by NA K pump

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does the outer and inner retina metabolism differ

A

Outer retina - 80% of glucose results in lactate formation - light decreases glucose consumption by reducing lactate.

Inner retina 70% of glucose is oxidized

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the highest oxygen consuming tissue retina or brain? What cells consume the most energy?

A

Retina

Photoreceptors - inner segments (ellipsoid), outer plexiformlayer, inner plexiform layer - synaptic terminals

17
Q

Where is the first synpase of the retina?

A

Outer plexiform layer

18
Q

Where is static information processed? Where is phasic information processed?

A

Static - outer plexiform layer

Phasic (movement) - inner plexiform layer

19
Q

What is the rod pathway?

A

Rod synaps with bipolar cell at OPL, this then snapses with amacrine cell and then ganglion cell

Take info to the LGN,

20
Q

What happens to photoreceptors in reposnse to light?

A

Hyperpolarise

Hyperpolarisation in OFF bipolar cells
Depolarisation in ON bipolar cells

21
Q

What are function of parasol and midget cells

A

P system codes for colour
M system repsonse to other stimuli

Detect reolution of fine detail and detection of general background illumination

22
Q

What is the rod photoreceptor pathway invovled in?

A

Vision in dim light (scotopic)

23
Q

How many rods? Cones? Ganglion cells?

A

120million rods
6 million cones
1 million ganglion cells

24
Q

What is convergence in rod system?

A

75000 rods drive 5000 ON depolarising bipolar cells and 250 amacine cells before converging on 1 ganglion cell

Increases sensitivity at the expense of resolution

25
Q

What is the cone pathway?

A

Cone photoreceptors contact bipolar cells which contact ganglion cells

Three types of cones

Cones can indicue hyperpolarisation or depolarisation in bipolar cells

For high resolution, foveal cone cells connect to a system of small bipolar and ganglion cells - midget cell system
Minimal convergence - midget ganglion cells project to individual parvocellular layer of LGN

26
Q

What are functions of RPE?

A

Photoreceptor renewal
Retinal attachment
Interphotoreceptor matric production
TRansport of water and metabolistes
REtinoid metabolism
Blood retinal barrier
Immunoregulation
Free radical scavenging

27
Q

What is the strucutre of the RPE

A

Monolayer of hexagonal cuboidal cells

Pigment granules in apical cytoplasm

28
Q

How does transport occur in the RPE

A

Tight junctions between RPE cells so transport occurs through them

NA K pumpst to generate sodium gradient and drive other transport systems by active transport

RPE absorbs water 2ml per 24h

29
Q

What are muller cells?

A

Glial cells of retina extend through whole thickness of retina

MAny fine processes which cover most surfaces of neuron cell bodies in nuclear layers and dendritic processes in plexiform layers

INSULATES electrically and cehmically

30
Q

What are functions of muller cells

A

Insulate retinal neurones
Structural support
Regulate extracellular environment of retina by buffering light evoked variation of K+ concentration
Take up glutamate form extracellular space
Store glycogen
Provide glucose to retinal neurones

31
Q

What is the choroid?

A

Lymphovascular supply of posterior segment, for nourishing overlying retina

Blood vessels in loose CT with type III 3 collagen

No lymphatics but immune cells inc mast cells, macrophages, dendritic cells

32
Q

what is the choriocapillaris?

A

Highly fenestrated leaky blood vessels
Drain into four vortex veins one in each quadrant of globe

Necessary permeatbilty to keep high glucose concentration at RPE and supply amino acids for producing vitamin A

33
Q

What forms the blood retina barrier?

A

Zonula occludens between endothelial cells - tight junctions
Tight junctions of RPE cells

There is a defect in the blood retinal barrier at the optic disc where water soluble substances enter the anterior optic nerve by diffusion form the extravascular space of choroid

34
Q

What happens in phototransduction

A

11-cis-retinal to all-trans-retinal

Transducin coverts GDP to GTP

Sodium channels close and cause hyperpolarisation

35
Q

What is the macula defined as hitologically/

A

Area of retina where ganglion cell layer is more than one cell thick

36
Q

What is the percentage of oxygen transfer in choroidal capillaries

A

Low
5-10%
High blood flow rate
Drains into vortex veins

37
Q

How long does it take for migration of disc from base of rod to outersegment to where it is shed

A

10 days

38
Q

What is maximal spectral sensitivity of the rod, cones

A

Rod 496nm (blue green)

Blue cone 440nm

Green cone 535nm

Red cone 570nm

Physiology (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions