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OAP B > RETINA > Flashcards

RETINA Flashcards

1
Q

WHAT IS THE VASCULAR TUNIC OF EYE?

A

CHOROID

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2
Q

WHEN ENTERING A DARK ROOM ON A SUNNY DAY, TAKES SOME TIME TO BE ABLE TO SEE, WHY?

A

TAKES TIME FOR RETINA TO REBUILD ITS RHODOPSIN

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3
Q

INTRAOCULAR PRESSURE PRIMARILY DUE TO WHAT?

A

AQUEOUS HUMOUR

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4
Q

AS NERVE FIBRES EXTEND FROM RETINA TO BRAIN…

A

FROM NASAL HALF OF EACH RETINA CROSS TO REACH THE OPPOSITE VISUAL CORTEX

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5
Q

WHICH CRANIAL NERVE CARRIES VISUAL IMPULSES TO BRAIN?

A

II (OPTIC)

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6
Q

CONSTRICTION OF PUPIL BROUGHT ABOUT BY CONTRACTION OF?

A

CIRCULAR MUSCLE OF IRIS

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7
Q

PHOTOPIGMENT IN RODS + CONES IS EMBEDDED IN THE?

A

MEMBRANE FOLDS OF THE OUTER SEGMENT OF THESE CELLS

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8
Q

IN DAYLIGHT, RODS CONTRIBUTE LITTLE TO VISION BECAUSE?

A

THE RHODOPSIN IS BLEACHED AS FAST AS IT IS REGENERATED

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9
Q

WHEN LIGHT HITS THE RODS..

A

NA+ CHANNELS CLOSE + LESS INHIBITORY NEUROTRANSMITTER IS RELEASED

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10
Q

TRANSDUCTION

A

light -> electrical potential

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11
Q

ENCODING

A

electrical potentials -> action potential sequences for retinal output

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12
Q

TEN LAYERS OF RETINA

A 
inner limiting membrane 
nerve fibre layer 
ganglion cell layer
inner plexiform layer
inner nuclear layer
outer plexiform layer
outer nuclear layer 
outer limiting membrane
photoreceptor layer
retinal pigmented epithelium
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13
Q

PARAFOVEA

A

rods + cones

inner + outer nuclear layers

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14
Q

PERIFOVEA

A

all retinal layers

thickest part

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15
Q

FOVEA

A

depression with inner retinal layers pushed aside

foveola - only long, slender cone outer segments

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16
Q

FUNCTIONS OF RPE

A
  • light absorption
  • epithelial transport
  • active potassium transport
  • vitamin A metabolism (visual cycle)
  • photoreceptor membrane recycling (phagocystosis)
  • hormone production + secretion
17
Q

RETINAL

A

small molecule made by modifying vitamin A

photons of light are absorbed by a transformation of retinal in photoreceptor membranes

retinal transformed in the rods is restored to its active state by enzymes in RPE

18
Q

RODS

A

110-130 million/ retina

long, slim cells

separate membrane discs

slow to respond

very sensitive

19
Q

CONES

A

5-7 million/ retina

wider cells

outer segment membrane continuous with plasma membrane

respond quickly

20
Q

RHODOPSIN

A

only in rods

a G-protein-coupled receptor

21
Q

PHOTOTRANSDUCTION IN DARKNESS

A

rod photoreceptors release the neurotransmitter GLUTAMATE

this inhibits bipolar cells from transmitting signals to ganglion cells which provide output from retina to brain

22
Q

PHOTOTRANSDUCTION IN LIGHT

A

rod photoreceptors are bleached + hyperpolarise

glutamate production stops + a sign reversal occurs in some bipolar cells that are excited into sending signals to ganglion cells which provide output from retina to brain

light is the ligand that triggers activation of the enzyme

23
Q

PHOTOTRANSDUCTION IN RODS

A

1 - activation of rhodopsin (R->R*)
2 - activation of transducin (G protein)
3 - activation of phosphodiesterase
4 - deactivation of chemical messenger, cyclic guanosine monophosphate (cGMP) closes cell

24
Q

OUTER PLEXIFORM LAYER

A

code neural signals for contrast (centre vs surround)

establish separate channels for detecting lighter objects + darker objects (ON vs OFF channels)

25
Q

WHAT IS NUCLEAR LAYERS MADE UP OF?

A

horizontal
amacrine
muller
bipolar cells

26
Q

WHAT IS PLEXIFORM LAYER MADE UP OF?

A

synapses

27
Q

RECEPTIVE FIELD

A

area of visual field that causes a response from a visual neuron (i.e. not necessarily the location of the cell)

28
Q

WHERE DO RODS + CONES SYNAPSE WITH INTEGRATOR NEURONS?

A

OUTER PLEXIFORM LAYER

29
Q

HORIZONTAL CELLS

A

communicate in outer plexiform layer

connect rods + cones with bipolar cells

30
Q

WHAT IS THE SIMPLEST + FASTEST PATHWAY FOR TRANSMISSION OF A SIGNAL?

A

CONE -> BIPOLAR CELL -> GANGLION CELL

31
Q

VISUAL PATHWAY

A

OPTIC NERVE (II)

  • > OPTIC CHIASM
  • > OPTIC TRACT
  • > LATERAL GENICULATE NUCLEUS OF THALAMUS
  • > OPTIC RADIATION
  • > PRIMARY VISUAL AREA OF VISUAL CORTEX IN OCCIPITAL LOBE
32
Q

MULLER CELL FUNCTIONS

A
  1. support metabolism to fuel aerobic production in nerve cells
  2. mops up neural waste products e.g. CO2 + NH3
  3. protects neurons from exposure to excess neurotransmitters e.g. glutamate (uptake + recycling mechanisms)
  4. control homeostasis + protect neurons by maintaining ionic environment
  5. regulation of K+ distribution across retinal vitreous border
33
Q

RPE - LIGHT ABSORPTION

A

melanin pigment granules absorb stray light

reduces light scatter from behind retina + between photoreceptors (apical processes)

improves resolution

34
Q

RPE - EPITHELIAL TRANSPORT

A

active import from CC:
- glucose, omega-3 fats, vit A

diffusion from CC:
- water + oxygen

active export to CC:
- waste products e.g. lactic acid

diffusion to CC:
- water, co2 + chloride

35
Q

RPE - ACTIVE POTASSIUM TRANSPORT

A

glial cell functions

ion levels must be stable for photoreceptors to function

ions rapidly exchanged during light-dependent activity

rapid ion compensation mechanisms in outer retina are by RPE cells + by muller cells in inner retina

36
Q

RPE - VITAMIN A METABOLISM

A

visual cycle

‘retinal’ is a small molecule made by modifying vitamin A

photons of light absorbed by a transformation of retinal in photoreceptor membranes

retinal transformed in rods is restored to its active state by enzymes in RPE

37
Q

RPE - PHOTORECEPTOR MEMBRANE RECYCLING

A

phagocytosis

photoreceptor membranes produces continuously + shed outer segments:

rod outer segments shed in morning (1-2 hours after dawn)

cone outer segments shed at night (3-5 hours after dark)

38
Q

RPE - HORMONE PRODUCTION + SECRETION

A

RPE produces + secretes a variety of factors + signalling molecules for regulation of metabolism, reactions to pathology/ injury etc

VEGF (vascular endothelial growth factor) - involved in making new blood vessels: angiogenic factor

PEDF (pigmented epithelium derived factor) - does opposite: antiangiogenic + neurotrophic protein of eye

OAP B (14 decks)

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