The document summarizes the structure and function of the retina. It describes the 11 layers of the retina, including the pigmented layer that contains melanin and prevents light reflection. It discusses the roles of rods and cones in vision, including color vision mediated by red, green, and blue cones. The retina contains specialized cone cells in the fovea that provide high visual acuity. Dark and light adaptation involve changes in rods, cones, pupil size, and neural pathways. The document also outlines the photoreception process in rods and cones and how this leads to a hyperpolarized receptor potential.
Retinal Pigment epithelial cells perform a multitude of functions to protect the retina and maintain normal vision. Any kind of RPE malfunction leads to a variety of ocular diseases.
This PPT explains the various functions performed by RPE to maintain normal vision.
Retinal Pigment epithelial cells perform a multitude of functions to protect the retina and maintain normal vision. Any kind of RPE malfunction leads to a variety of ocular diseases.
This PPT explains the various functions performed by RPE to maintain normal vision.
This is an Educational presentation on mechanism of vision. In this presentation layers of retina, process of transduction and electrical signals generation is well explained and finally optic nerve pathway is well illustrated.
21. Excitation of the photo receptors
• Excitation of the rod causes increased negativity
of the intrarod membrane potential, which is a
state of hyperpolarization, there are more
negativity than normal inside the rod membrane.
• This is opposite to the decreased negativity thatopposite to the decreased negativity that
occurs in other sensory receptors.occurs in other sensory receptors.
• When rhodopsin(visual purple) at the outer
segment of the rod decomposes by light, the
conductance of sodium decreases at the outer
segment.
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22. Excitation of the photo receptors
• Sodium ions continued to be pumped
outward through the membrane of the inner
segment.
• More sodium ion leave than leave back, there
will be more negativity inside causing greater
hyperpolarization
• At maximum light intensity, the membrane
potential approaches -70 to-80 millivolts
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23. Rod under dark condition
• The inner segment of the rod continually
pump sodium from inside the rod to the
outside, creating negative potential on the
inside of the entire cell.
• The outer segment of the rod is very leaky to
the sodium ion. Positively charged sodium
ions continually leak back. There is reduced
electronegativity inside measuring about -40
millivolts
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24. Hyperpolarization receptor potential
• Both rods and cones go
through hyperpolarization.
• The bipolar and horizontal
cells become depolarized by
inhibitory neurotransmitter;
and they are hyperpolarized
by excitatory
neurotransmitter.
• Decreased c-GMP causes
hyperpolarization of rods and
cones
• Neurotransmitters are
released by hyperpolarization
of rods and cones
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