Animal physiology, gyton and hall, structure of eye, retina

1. W E L C O M E
THE SENSE OF
VISION
A PRESENTATION BY:
MUHAMMMAD SOHAIB
RANA ZAIN ALI
PRESENTED TO:
PROF. WAJIHAASIF

2. TABLE OF CONTENTS
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 Anatomy of eye
 Neural function of eye
 Photochemistry of vision

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5.  Superior oblique muscle
 Inferior oblique muscle
 Superior rectus muscle
 Inferior rectus muscle
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EXTRAOCULAR MUSCLES
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7.  PRINCIPAL FOCUS
The point on the axis of a lens or mirror to which parallel rays of
light converge or from which they appear to diverge after refraction
or reflection.
 FOCAL LENGTH
Focal length of a lens is the distance between centre of lens and
focal point . Focal point is a point on principal axis , at which light
rays meet after refraction through lens.
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8. Human eye is composed of four refractive interfaces:
1. The interface between the air and the anterior surface of cornea.
2. The interface between the posterior surface of cornea and the aqueous humor.
3. The interface between the aqueous humor and the anterior surface of the lens.
4. The interface between the posterior surface of the lens and the vitreous humor.
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IMAGE FORMATION IN HUMAN
EYE
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9. ACCOMMODATION
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10. NEAR SIGHTEDNESS
 FAR SIGHTEDNESS
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DISEASES
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11.  DEUTERANOPIA ( Green )
 PROFTANOPIA ( Red )
 TRITANOPIA ( Blue )
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COLOR BLINDNESS

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13. 1. LAYERS OF RETINA
 Pigmented layer
• Melanin pigment
• Prevent light reflection & enhances visual acuity
• Also stores Vitamin A
• Albinos lack melanin
 Layers of rods and cones
 Outer nuclear layer
 Outer plexiform layer
 Inner nuclear layer
 Inner plexiform layer
 Ganglionic layer
 Layer of optic nerve fibers
 Inner limiting membrane
ANATOMY AND FUNCTIONS OF
RETINA
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14. SNELLEN EYE CHART
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15. 2. FOVEAL REGION
• Minute area in the centre of retina ( 1 mm2 )
• Cones with slender and long bodies
• Rods are absent
• Blood vessels, ganglion cells, inner nuclear layer of cells and plexiform
layer are displaced aside
• Provides acute and detailed vision
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ANATOMY AND FUNCTIONS OF
RETINA
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16. 3. RODS & CONES
• Rods are longer and narrower ( 2 – 5 mm in peripheral retina)
• Cones are shorter and broader ( 5 – 8 mm in peripheral retina )
• Rods contain Rhodopsin
• Cones contain Iodopsin ( color pigment )
 PARTS OF RODS AND CONES
o Outer segment
• Discs of folded cell membrane ( 1000 )
• Photochemical pigment ( 40% )
o Inner segment
• Mitochondria which provides energy
• Other cytoplasmic organelles
o Synaptic body
• Connect to neuronal cells, horizontal and bipolar cells
COURTESY: ZAIN & SOHAIB
ANATOMY AND FUNCTIONS OF
RETINA
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NEURAL FUNCTION OF RETINA
 THE PHOTORECEPTORS ( RODS AND CONES )
• Transmit signals to outer plexiform layer
• Synapse with bipolar and horizontal cells
 THE HORIZONTIAL CELLS
• Transmit signals horizontally from rods and cones to
bipolar cells
 THE BIPOLAR CELLS
• Transmit signals from rods & horizontal cells to inner
plexiform layer
• Synapse with ganglion cells and amacrine cells
 THE AMACRINE CELLS
• Transmit signals from bipolar cells to amacrine cells
 THE GANGLION CELLS
• Transmit output signals from retina through optic
nerve to brain
 THE INTERPLEXIFORM CELLS
• Transmit signals in retrograde direction ( from inner
to outer plexiform layer )
• Inhibitory signals control the lateral spread of signals
by horizontal cells
• Control degree of contrast in the visual image
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PHOTOCHEMISTRY OF VISION
Fig: The rhodopsin - retinal visual cycle
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19. EXCITATION OF ROD WHEN RHODOPSIN IS
ACTIVATED BY LIGHT
• The rod receptor potential is
Hyperpolarization, Not Depolarization
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PHOTOCHEMISTRY OF VISION
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21. WHY DO WE HAVE TWO EYES?
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