In this part I will talk about the histology and physiology of the retina;And its photoreceptor.

1. THE RETINA
In this part I will talk about the histology and physiology of
the retina
And its photoreceptor.

2. THE RETINA
INTHE RETINA there is two type of photoreceptor
1.The cons which more sensitive to color
2.The rods which more sensitive to B/W

3. Cods and rods

4. THE DIFFERANCE
The rods dose not take more light rather than
the con will take a lot
So the use of this cell depended on the amount
of the light which transported to the retina

5. THE DIFFERENCE
IF you look to some one in dim you start to see
a little details as you cant see much details as
you would if there was a lot of light out side

6. THE DIFFERENCE
THE REASON IS the amplification of the signal
because many rods are connecting to on
nervous path way to brain so this enough that the
photo hits of these handereds rods to send signal
to brain.

7. THE DIFFERANCE
BUT in the case of cons only a few of them are
connecting to one path way so lower ampilification
of the cons mean also an improvement in the
resolution to give clearly in details and colors.

8. THE DIFFERENCE
 SOWE CAN SAY : that the activity of any type
of the cells of the retina stimulated by two
factors:
 1- the quantity of light and we explain it.
 2- ???

9. THE DIFFERENCE
 THE 2 FACTORE IS :
The distribution of cons
and rods in retina .
The cons is more than
rod in fovea .
So if the light comes with
direct spectrum so the
picture will be clearly and
in details .

10. THE DIFFERANCE
BUT if I look to something
that is not in the direct of
my vision I will see it but
with no clear vision
(penumbra).

11. HISTOLOGY OF RETINA
We will take about the histology
of the retina rapidly.
Histologically, the retina can be
divided into 10 layers
And all of this found in the hand
book but I will talk about the cell
of layers which is very important
to
Distinguish the color:

12. Histologically, the retina can be divided into 10 layers (Kolb et al., 1995) (Figure 2). From the inner
to the outer part of the retina, these retinal layers are organized as follows.The first layer, the
inner limiting membrane (ILM) is formed by the conical endfeet of the Müller cells and astrocytes.
The second layer, the nerve fiber layer (NFL) consists of axons of ganglion cells, retinal vessels
and glial cells.The third layer, the ganglion cell layer (GCL) predominantly contains the nucleus
of ganglion cells, vessel cells, glial cells, and some displaced amacrine cells.The forth layer is the
inner plexiform layer (IPL) where bipolar, amacrine, and ganglion cells interact.The fifth layer,
the inner nuclear layer (INL) harbors the nuclei from bipolar, horizontal, amacrine, and Muller
cells.The sixth layer is the outer plexiform layer (OPL) where photoreceptor cells connect with
bipolar cells, and where horizontal cells interact closely with both photoreceptors and bipolar
cells.The seventh layer, the outer nuclear layer (ONL) contains nuclei from photoreceptor cells.
The eighth layer, the outer limiting membrane (OLM) is created by junctional complexes between
adjacent Muller cells as well as between Muller and photoreceptor cells.The ninth layer, the
photoreceptor layer (PL) contains tightly stacked cones and rods forming a pallisading layer of
photoreceptors.The tenth layer results from tight junctional complexes between RPE cells
forming a continuous RPE monolayer. Moreover, the RPE is separated from the choriocapillaris by
the Bruch's membrane composed of 5 layers: the basement membrane of the choriocapillaries, an
outer collagenous layer, a central elastic layer, an inner collagenous layer, and the basement
membrane of the RPE. Basically, photons first pass through the neuroretina before activating the
photoreceptor cells. A reduction in the circulating current triggers a change in the excitatory
signaling to bipolar cells and subsequently ganglion cells. Bipolar and ganglion cell responses are
modulated by horizontal and amacrine cells responses, respectively. Ganglion cell axons
converge to form the optic nerve which carries the signal to the brain ( in hand

13. histology
 THERE is three main
layer of nerve cells
 1- the outer layer is a
photoreceptor layer
which is very important
to detect the light and
there is a cons which is
classification to S/M/L

14. HISTOLOGY
 S mean sense to short
wave length like blue.
 M mean sense to
medium wave length
like green .
 L mean sense to long
wave length like red.

15. HISTOLOGY
 INTHE MIDDLE layer:
Contain 1- bipolar cells
which transport impulse
from outer layer to the
inner layer.
2- the horizontal cell
3-the amacrine cell

16. Question ?
If we know that the light impossible to mixing
and we have only three type of cons for
so how can we detect the other color
like yellow ,brown and etc…..

17. ANSWER
IFWE LOOKINGTO SOMETHING WITHYELLOW
COLORTHAT’S NOT MEANTHIS CAR OR BALL
Reflect the yellow color because there is no mixing in
the wave length but it reflect the red and the green
color (700 and 540) wave length I have
confirmed this phase because the
determination of color is a variable from
one to another . And for this rang of
wave some cons will be stimuli to creates
impulse for red wave and impulse for
green wave so where the yellow
color??

18. The retina dose not tell us how this is work so I will look
to early visual cortex in the brain (that’s mean
color is a special effect added on
what you see by your brain
“experience” with the help of 3
teams of special detectors in your
eyes)

19. HISTOLOGY
Horizontal cells are the laterally interconnecting neurons having
cell bodies in the inner nuclear layer of the retina of vertebrate
eyes.They help integrate and regulate the input from multiple
photoreceptor cells

20. HISTOLOGY
 Amacrine cells are interneurons in the retina.[1]They are
named from the Greek roots a– ("non"), makr– ("long")
and in– ("fiber"), because of their short neuritic
processes. Amacrine cells are inhibitory neurons, and
project their dendritic arbors to the inner plexiform layer
(IPL), there interacting with retinal ganglion cells and/or
bipolar cells.

21. HISTOLOGY
 THE inner layer : ganglions cells the have an
tall appendage called axon and form the optic
nerve which lead to brain.

24. THE PHYSIOLOGY
BEFOR I begin I want you to know that the
process that happen in the rods and the cons are
relatively similar and the difference in the sense
come from the difference in the chemical
composition .
Lets start

25. THE
PHYSIOLOGY
So here we are
inside the rod and
we find the major
thing that we
need and there
are three main
thing
1.Rhodopsin
2.Trimeric of
transducin
3.Aphosphodiest
erase

26. THE PHYSIOLOGY
1.Rhodopsin is a visual pigment that’s found in
the rods and composed of two molecule
a. Opsin (protein)
b. Retinol in cis form (inactive)
Retinol is aversion of vitamin A
This explains part of the reason
Why vitamin A help with vision.

27. THE PHYSIOLOGY
2- we have a trimeric molecule meaning it has
three subunits (transducin).

28. THE PHYSIOLOGY
3- the phosphodiesterase molecule

29. THE PHYSIOLOGY
 THE PROCESS : 1- IFTHE LIGHT comes in
and strikes rhodopsin so the cis- retinol will
change to another type called trans –retinol
which loss of its attraction for the opsin
molecule and exposed anew binding site in
opsin
OPSIN
CIS-
RETINOL
TRANS-
RETINOL
OPSIN

30. THE PHYSIOLOGY
 The binding site in Opsin can catalyzeThe
reaction of transducin that convert GDPTO
GTP and then leave the other two alpha
subunit of phosphodiesterase .
OPSIN
GDP
OPSIN
GT
P
TRANCDUSIN TRANCDUSIN

31. THE PHYSIOLOGY
 Then it removes that alpha subunit so you
can see that the goal was to free up this alpha
subunit .
PHOSPHDIASTERA
SE
GT
P
PHOSPHDIAST
ERASE

32. THE PHYSIOLOGY
 As we can see here there is only one alpha
subunit removed but we still have one more
alpha subunit in order
PHOSPHODISTA
ES

33. THE PHYSIOLOGY
 To remove this second alpha subunit we need
another GTP so we need two process of
activation to release one phosphodiesterase
PHOSPHODISTE
RASE
GTP
PHOSPHODIS
TERASE
THE MAIN MOLECULE

34. THE PHYSIOLOGY
 The phosphodisterase will convert CGMP--
TO GMP.WE know that the CGMP gated NA+
channel . *if sodium will rush in the membrane,
it will depolarize and the neurotransmitter will
Realized. *if phosphodiesterase is activated no
release of transmitter.

35. THE PHYSIOLOGY
0
0.5
1
1.5
2
2.5
3
0 0.5 1 1.5 2 2.5 3
Y-Values
Y-Values
The repolarization

36. THE PHYSIOLOGY
 INTHE hyperpolarization the
neurotransmitter
Will not released (inhibited) which cause inhibit
in the membrane of bipolar cell .
If the neurotransmitter inhibited the bipolar cell
will depolarized .

37. THE PHYSIOLOGY
0
0.5
1
1.5
2
2.5
3
3.5
0 0.5 1 1.5 2 2.5 3
Y-Values
Y-Values
Depolarization
of bipolar cell

38. THE PHYSIOLOGY
0
0.5
1
1.5
2
2.5
3
3.5
0 1 2 3
Y-Values
Y-Values
Depol
arizati
on of
bipola
0
0.5
1
1.5
2
2.5
3
0 1 2 3
Y-Values
Y-Values
The repolarization

39. THE PHYSIOLOGY
 So the bipolar will release a neurotransmitter
to synapse between it and ganglion cell.

40. THE PHYSIOLOGY
 SO LETS RETURNTHE INFORMATION
1- response to light the rod will be hyper
polarized.
2- neurotransmitter.
3- depolarization to bipolar cell
4- neurotransmitter.
5-ganglionic cell will fire to depolarization the
impulse to the brain where it will be intrepid.

41.  Thank you
 BY MUSTAFAHIKMAT
SAEED D2