Physiology Of Vision with General Introduction Of EyE

1. Yashpal Singh Chundawat
Jai Narain Vyas University, Jodhpur
Zoology Department

2. Refraction of light entering
the eye
Focusing of image on the
ratina by accommodation
of lens
Convergence of image
Photo-chemical activity in
retina and conversion into
neural impulse
01
02
03
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2
Events
of Vision
05 Processing in brain and
perception

3. Overview Of Eye Anatomy

4. 01
02
03
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Sclera
# “White of the eye”. # Dense fibrous Connective tissue.
# Contains Blood Vessels and Insertion site for extrinsic Eye
Muscle.
Cornea
# Thin, transporting epithilium.
# Continuous with the sclera, covering iris and pupil.
Iris
# “Colored part” of the eye. # Creates and adjust the pupil.
# Contains blood vessels, pigment cells, loose connective
tissue and pupillary muscle. # Regulates amount of light.
Lens
# Focused image on the retina.
# Colsely-packed concentric columnar cells.

5. 05 06 07 08
Ciliary Body
# Ring of smooth muscle around lens.
# Regulates the shape of the lens for
accommodation.
Suspensatory Ligaments
# Attach the ciliary body to the lens
Retina
# Lines the posterior part of the eye.
# Held in place by the Vitrous.
# Contains light-sensitive photoreceptors.
Choroid
# Pigmented to absorb exess light.
# Supplies the retina with nutrient and
oxygen via blood supply.

6. WHEN WE DECIDE TO LOOK AT SOMETHING, A
BRAINSTEM STRUCTURE CALLED PONS CALLED
INTO ACTION. IT CONTROLS EYE MOVEMENT ,
CONSTANTLY TELLING OUR EYE MUSCLES TO
MOVE TOWARD THE COREECT STIMULUS OF
LIGHT.

7. Accomodation
● The process of changing the shape ofthe lens while
focusing on the object.
● At rest focusing on distant object, needs to increase focal
power to focus on close object.
● The ciliary muscles contract and release tension in the
ligament and the lens becomes rounder.
● The increased curvature increaes the focal point closer to
the eye.

8. Lens Correction

9. Transduces light into neural signals and
passes on the information to other region
of the brain.
Displaced portion of the CNS contains the
light-sensitive cells.
The Ratina 9
In addition to Phtoreceptors contain 4
additional types of neurons that form an
orderly intricate neural circuit.
While ganglion cells communicate via
action potentials, the photoreceptorsand
other neurons communicate via
gradeynaotic potentials that are
conducted electrically.
Arranged with the light-senseing photoreceptors at the very posterior edge of the eye
where they are located near the PE and choroid which assiasts in regeneration.

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The Retinal
Anatomy
Ganglion cells
- Axons generate the optic nerve.
- Send action potential to the thalamus.
1*106 cells in the retina.
Amacrine cells
- Synapse within the inner layer of the ratina.
- Interconnect bipolar cells and gagnglion cells.
- Regulate communication between the ganglion cells
and the photoreceptor.
Bipolar cells
- Directly connected photoreceptors
and gaglion cells in a radial direction.
Harizontal Cells
- Synapse within the outer layer of the retina.
- Interconnect photoreceptors with bipolar cells in a
horizontal direction.
-Mediate interactions over a wide area of the retina.

12. Photoreceptors
- Rods - Detect
amount of light
present.
- Cones - Detect color.
- Highest density of
cones at fovea.
Pigmented Epithilium
- Absorb excess light.
-Involved in photoreceptor
regeneration.
The Ratinal Anatomy

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• Central area of the retina with cone-mediated
vision.
• Neurons are displaced laterally to the fovea to
minimize scattering.
• Very high resolution vision, due to 1:1:1 ratio of
photoreceptor : bipolar ganglion : ganglion cell.
• At the periphery the ratio of photoceptors to
ganglion cells is high, cover a large receptive field.
• Cone levels fall to a very low density outside the
fovea, where the rods take over.
• Peripheral vision is mediated by both rods and
cones.

14. Photoreceptors
Cones
# Higher threshold receptors for photopic vision and color
vision.
Rods
#Low threshold receptors for night vision (scotopic vision).
Rhodopsin/Visual purpule.
#Visula pigment present in rods.
#Rhodopsin = opsin + retinine(11-cis retina/vit A aldehyde).

15. Phototransduction
Phenomena of
conversion of
light energy into
nerve impulse
Light falls on ratina -->
cause photochemical
changes --> trigger
cascade of biochemical
reaction --> generation
of electrical impulses.
Photochemical
Changes
Rhodopsin
bleaching
Rhodopsin
regeneration

18. 1. Activation of the receptor protein.
• In rods, that is rhodopsin.
1 Photon ------> 1 Rhodopsin
Opsin Prorein 11- trans-retinal
Confermational Charge
Transducin

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POLARIZED STATE
RESTING POTENTIAL
- 60 mev

20. Transducin
Phosphodierase(PDE)
Transducin
Na+

21. Sodium Channels
Ligant gated ion channel Voltage Gated Ion Channel

22. Na+
GTP
cGMP
Na+
By the action on Guanyl Cyclase enzyme
Ligand gated
ion Channel

23. Voltage gated ion gates Open
Voltage gated
ion channel
Na+ Na+ Na+
Threshold
potential
- 30 mev

25. Terminal Synaptic Vessicle
(NEURO-TRANSMETERS)
POST
SYNAPTIC

26. PRE SYNAPTIC
BIPOLAR CELL
GAGNLIONIC CELL

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REFERANCES
Our evolution
Ppt -
“EYE PHYSIOLOGY AND VISION”
BY Tabitha Schrufer
Ppt -“PHYSIOLOGY OF VISION”
Prof. Vajira Weerasinghe
University of Peradeniya
Textbook of
MEDICAL PHYSIOLOGY
G.K. Pal
www.Allaboutvision.com
Artical By : Adam Debrowski

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Thank You