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Special sense Physiology > Retina > Flashcards

Retina Flashcards

1
Q

بسم الله الرحمن الرحيم
__________________
Mention layers of Retina

A

Pigmented epithelium
Layer of phororeceptors
Outer limiting membrane
Outer nuclear Layer
Outer plexiform layer
Inner nuclear layer
inner plexiform layer
Ganglion cell layer
Optic nerve fibers
Inner limiting membrane

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2
Q

¶ Retina is transparent.
¶ Retina has no pain nerve supply → painless.
¶ The outer 5 layers of retina supplied from ???????
¶ The inner 5 layers of retina supplied from ???????
but there is no sufficient anastomosis between these vessels.
¶ Retina has no lymphatics.

A

Choroid blood vessels
_____________
inner retinal + choroid blood vessels

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3
Q

Mention nucelar cells of retina

A

Outer nuclear for ( Rods and cones nuclei
Inner nuclear for ( Bipolar + horizontal + amacrine
Gagnlion cell layer

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4
Q

retinal detachment is damaging to the receptors. of rods and cones why?

A

Because Rods and cones receptors are supplied by Capillary pleux in the choroid

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5
Q

Bipolar and ganglion cells are supplied by?

A

Retinal blood vessels

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6
Q

A single melanin containing cell layer in a direct contact with
choroid.
Mention it and its functions

A

Pigmented epitehlium layer ASP

____________________-
-Absoprtion of extra light cannor bea absorbed by Rods and cones photoreceptors preventing Ligth reflection
-Storage of Lare quantities of Vit A
-Phagocytosis of membrene discs and debris of photoreceptors

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7
Q

Inner nuclear layer of Retina explain

A

Formed of Bipolar cells + Amacrine + Horizontal
Muller
____________________________________
Bipolar receive imupulse from Photorecpetors or Horiztontal cells to sends it to Ganglion cells
1-directly
2-indirectly thorugh amacrine cells
_______________–
Bipolar cells are the First 1st order neuron

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8
Q

Mention types of Bipolar cells

A

Depolarizing due to stimulation by Photoreceptros Glutamate
Hyperpolarizing due to inhibtion by Horizontal cell GABA

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9
Q

Mention functions of Bipolar cells

A

1-First 1st order neruon of Visual pathway
2-Contrast due to Lateral inhibtion

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10
Q

Mention functions of Horizontal cells

A

Most imp cell of lateral inhibtion receving from Photoreceptors
_________________________________
Lateral inhibtion of Weakley or non stimulated Pathways = Enhancement of Contrast +sharpening of borders
Lateral inhibtion of some color specific ganglion cells for color differentiation

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11
Q

Mention functions of amacrine cells

A

Carries impulses from bipolar to ganglion cells
Resonsible for Sharpening of Vision + Vision analysis
Onset of visual signals
Offset of Visual signals
Bilateral amacrine cells respnds to movement of a spot across retina in a specific direction

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12
Q

Mention functons of Muller cells >

A

Forming outer &inner limiting membranes
Retinal metabolism in
-storing Glycogen
-Removal of debris + uptake of NTs

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13
Q

The Ganglion cells:
????? order neurons in visual pathway
 Receive impulses from?????& ?????cells.
 Their axons form o????????
 Continuously transmit impulses to the brain.

A

2nd order Neuron
______________
Bipolar + Amacrine
__________________-
Optic nerve fibers

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14
Q

Compare between Magnocellular and parvocellular Ganglion cells ( حجم مجال منتهي مسئولية”

A

Size:
Magno: Large rapid
Parvo : small slower
________________
Receptice field:
Magno Large less acuity
Parvo : small more acuity
_____________________
Projecto to ?
Magno to Magnoceulluar layer of LGB
Parvo to parcocellular layer of LGB
________________________
Respnisible for :
Magno for Movement + Light intensity
Parvo for Boundaries + edges + Details

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15
Q

Particular area of retina sending impulses to certain Bipolar + Ganglion cells

A

Receptive field
Large in Magnocellular so less acuity so for movement and ligth inetensity
Less in parcocellular so high acuity so for Details + boundaries and edges

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16
Q

Optic disc ( physiological blind spot):
 1.5 mm in diameter.
 3 mm …….to the center of retina.
Why called blind spot ?
 Pale pink, well defined, has a physiologic cup.
 At which:
???
1-
2-
3-

A

Medial to center
______________
blind spot as it is insensitive to light and has no photoreceptors
_________________________-
At which
All retinal layers end except ? Ganglion cell fibers
Retinal vessels enter
Optic nerve exit

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17
Q

Optic disc abnormailtis :-
a) ↑ cupping: by?????
b) Swelling (papilledema): by ??????
c) White disc with deep cupping: ????

A

a)Increased IOP
b)Increased Intracranial pressure
c) Optic atrophy

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18
Q

Macula lutea:
 Yellowish spot at the center of retina.
 Contains MAINLY???photoreceptor
 Contains ?????, which is a special type of melanin that:
??????
1-
2-
3-

A

Cones
___________
Xanthopyll
______________
1-Absorb extra light
2-Xanthopyll works as antioxidant
3-Xanthopyll prtoects photorecptors by filtring UV rays

19
Q

Area of sharpest vision ?
site?
photorecpetos?

A

Fovea centralis
Center of Macula lutea (center of center of vision)
Photorecpetors : = Cones only 1:1 to bipolar cells

19
Q

GR/Fovea centralis is the sharpest vision area

A

Contains only cones!
Light falls directly on cones due to no BVs + layers of retina are displaced to sides
Each cone connected to one Bipolar to single Ganglion to single optic nerve fiber 1:1 with no convergence for more sharpness
Pigmented Xanthopyll epithelium

20
Q

Donut vision explain

A

When there is age related mauclr degneration which is degeneration of photoreceptors in Macula +Fovea
this leads to :
Loss of central shapest vision
Perservation of less sharp Periopheral vision
causing Donut vision

20
Q

Compare between Fovea and Extra Foval regions
in
1-Receptors
2-Connections

A

Receptors :
Fovea: Only small cones
ExtraF: Rods mainly + large cones
__________________________________
Connections:
Fovea : 1:1:1 single cone to single bipolar to single ganglion cell
ExtraF: 200 -300 receptors : 1 bipolar
5 bipolar : 1 ganglion

21
Q

Compare between fovea and extra foveal region in
Nutirition

A

Fovea: Avascular depends on choroid Capillary by diffusion
ExtraFovea: Choroid and Retinal BVs

22
Q

Compare between Fovea + extra fovea in
Sensitivity
Threshold
Acuity
Colors
Vision

A

Sensitivtiy and threshold and acuity:
Fovea less sensitive with high threshold and high acuity of vision so diffentiate colors and used in Photopic vision =vision of the day

ExtraFovea :more sensitive with less thresholld and low acuity so cannot differentiate colors for Scotopic vision dim light of night +photopic also

23
Q

List segments Photoreceptors

A

Outer segment :- Contains 1000 discs containing Photosensitive pigments as shelvels in Cones and Separated by membranes in Rods
Inner segments: Mitochondria
Nucelus
Synaptic body

24
Q

Photosnestive chemical or substance or pigments conisits of ??

A

1-Opsin : serpntine carrier protein
Scotopsin in rods
Photopsin in cones
2-Vit A = 11 Cis Retinal

25
Q

What happens in case of Vit A def ?

A

4D
Dark adapation failure = Night blindenss =nyctalopia
Degenration of Cones
Degentaion of retinal neeural layers
Dryness of eye and damage to cornea called Xeropthalmia

26
Q

Compre between Rods and cones in
Number + Distribution

A

Rodes 120 million mainly in peripheral less in center absent in fovea
Cones 6 million mainly in Fovea and center less in peripheral

27
Q

Compare between rods and cones in Connections + photosensitve pigments

A

Rods : 200-300 receptors with ? 1 bipolar cell
Have iodopsin or Scotopsin for night vision
Cones : 1 receptro to 1 bipolar celss 1:1 ratio
Have Rhodopsin or photopsin for Day detalied colored vision

28
Q

Compare between rods and cones
in
Sens-threshold-ACuity- color -

A

Rods : more sensitive less thrshold with less acuity cannot differentiate colors so used in night vision
Cones: less sensitive more threshold more acuity differntiaintg colors so for detaild day colored vision

29
Q

Scotopsin found in … which functions are?

A

Rods
fucntions :
Scotopic nigh vision dim light vision
Peripheral vision

30
Q

Photopsin found in ,,,,,,, which functions are ?

A

Cones
Photopic day vision
central vision

31
Q

wHAT Type of changes occur when light falls on retina ?

A

1- Photochemical changes
2-phototransuction changes

32
Q

Describe bleaching of Phororeceptor pigment mechanism

A

When light falls on Rhodopsin
Rhodopsin conveteidin into ?
Bathorhodopsin - lumirhodopsin - Metarhodopisn 1 - meta rhosopsin 2 which is active Rhodopsin
Rhodopsin is separated into :
OPsin
All trans retinal straight chain unable to combine with rhodopsin

33
Q

all phtocemincal changes of the pigment are indpenednt on light except?

A

Conversion of 11 cis retinal to
All trans retinal

34
Q

How to regenerate Rhodopsin ?

A

1-Isomerase converting all trans retinal into 11 cis retinal
2-dehydrogenas converting all trans reinal into all tran Retionl then isomerase to 11 cis retional then reductase to 11 cis Retinal in Retinal pigmented Epithelium

35
Q

Describe state of photoreceptors during dark or resting state

A

The inner segment ouflows Na that ascends to the outersegment to enter it again by cGMP depednednt Na channels maintaining the Membrane potential at -40 mv which is partially polarized relasing GlUTAMATE inhibiotry transmitter to Bipolars

36
Q

What happens on light exposure on retina to phtoreceptors according phototransduction

A

MetRhodopsin II activated (Phospodiesterases) that breaks down cGMP causing Na channels closure so the membrane of receptor is hyperpolarized inhibiting Glutamate release causing disinhibtion of bipolar cells stimulating it to reach the optic nerve fiber of ganglion cell to brain

37
Q

The degree of hyperpolariztion of photorecptor membrane is directly proprtionate to ?

A

Logartithm of Light intensity
intensity change : 10x-100x-1000x
Membrane potenital change : 1x-2x-3x

38
Q

What happens to membrane potential on removal of light ?

A

Rhodopsin Kinase inactivates phosopdiestarse making it open for cGMP to be resynthesized so reopen of Na channels and restoring partilly deoplarized membrane potenial at -40mv
reinhibtion of bipolar cells by glutamate release

39
Q

Only retinal cells respond by action potential are ?

A

Ganglion cells
the other by locally graded local potential

40
Q

SO stimulation of photoreceptors cause?

A

Hyperpolarization and
decreased of NTs release so
disinhibiton of visual pathway

41
Q

 Receptor potential α logarithm of light intensity
why?????
 Receptor potential in rods:
 Reaches a peak in 0.3 seconds
 Lasts for more than 1 second.
 Cone responses are 4 time faster than rods.

A

To help discrimniation a wide range of Light intesnisty

42
Q

” رب هب لي حكما وألحقني بالصالحين “

A

Special sense Physiology (8 decks)

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