PHOTORECEPTORS CELLS.pptx
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Rods and cones are photoreceptor cells that assist in vision by absorbing light and converting it into signals that trigger changes in membrane potential. Rods and cones differ in structure and function, with rods being more sensitive to light but unable to distinguish colors, and cones providing color vision but requiring brighter light. The document goes on to discuss the distribution and specific functions of rods and cones in vision.
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Visual pathway
The visual pathway conveys visual signals from the retina to the visual cortex. Light is detected by photoreceptors (rods and cones) and converted to electrical signals. These signals pass through bipolar and ganglion cells in the retina and then through the optic nerve, optic chiasm, optic tracts and lateral geniculate body to the visual cortex via the optic radiations. Lesions along this pathway can cause different visual field defects including hemianopia and quadrantic defects depending on the location of the lesion. Common causes of lesions include tumors, vascular abnormalities and infections.
PHYSIOLOGY OF VISION
This document summarizes the physiology of vision. It discusses:
1) How visual impulses are processed and transmitted from photoreceptors in the retina through the visual pathway to the visual cortex.
2) The types of cells involved in retinal processing and their functions, including rods, cones, horizontal cells, bipolar cells, amacrine cells and ganglion cells.
3) How visual signals are transmitted from the retina through the optic nerve, lateral geniculate body, and optic radiations to the primary visual cortex.
4) The layers and connections of the primary visual cortex and properties of simple, complex and hypercomplex cells in the visual cortex.
Retina
The retinal anatomy document summarizes the layers and structures of the retina. It notes that the retina consists of 10 distinct layers, including the retinal pigment epithelium, photoreceptor layer, and ganglion cell layer. It describes landmarks such as the macula lutea, fovea centralis, and optic disc. The document also discusses the blood supply to the retina from the central retinal artery and choroidal capillaries, as well as the neuroglial and neurotransmitter components of the retina.
visual pathway
The visual pathway begins when light enters the eye and strikes the retina. Optic nerve fibers carry the visual information from the retina to the optic chiasm, where fibers from the nasal retina cross over. The fibers then continue along the optic tracts to the lateral geniculate bodies before projecting to the primary visual cortex via the optic radiations. The primary visual cortex is located in the occipital lobe.
Physiology retina
The retinal pigment epithelium (RPE) performs several important functions to support photoreceptor cells in the retina. It acts as a barrier between the retina and choroid, transports nutrients between the retina and blood vessels, regulates the subretinal space ion concentration, engages in the visual cycle to regenerate photopigments, and phagocytoses shed photoreceptor outer segments. Phototransduction is the process where photons are converted to electrical signals in the photoreceptor cells. It involves photoisomerization of rhodopsin triggering a biochemical cascade that modulates cyclic GMP levels and closes cation channels, ultimately leading to hyperpolarization.
Embryology of the human eye
The development of the human eye begins around day 22 of gestation as the optic vesicle forms laterally from the prosencephalon. The optic vesicle invaginates and contacts the overlying surface ectoderm to form the lens placode. By day 33, the lens vesicle separates from the surface ectoderm. The optic vesicle then forms the double-layered optic cup, with the lens vesicle embedded within. Various ocular structures develop from the optic cup, surface ectoderm, and surrounding mesenchyme including the retina, lens, cornea, iris, ciliary body, and more. The development of the eye is complete by birth.
Light and Dark Adaptation
This document discusses light and dark adaptation in the eye. It describes how the eye adjusts to bright light through light adaptation over 1-10 minutes as cones take over from rods. Dark adaptation is the eye's ability to recover sensitivity in low light after exposure to bright light, which can take rods up to 30-35 minutes. The mechanisms that allow vision over a wide range of light levels include pupil changes, rods and cones in the duplex retina, dark adaptation, and light adaptation of the visual system. Dark adaptometry is used clinically to diagnose retinal disorders by measuring dark adaptation recovery curves.
Light and dark adaptation chinnu
This document discusses light and dark adaptation in the visual system. It describes the roles of rods and cones in scotopic and photopic vision. Dark adaptation allows the visual system to adjust to low light levels and involves both rods and cones, with rods taking longer to recover sensitivity after being bleached. The document outlines the dark adaptation curve and factors that influence it such as pre-adapting light intensity and duration. Light adaptation occurs more quickly and allows the visual system to function across a wide range of background illuminations.
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1) How visual impulses are processed and transmitted from photoreceptors in the retina through the visual pathway to the visual cortex.
2) The types of cells involved in retinal processing and their functions, including rods, cones, horizontal cells, bipolar cells, amacrine cells and ganglion cells.
3) How visual signals are transmitted from the retina through the optic nerve, lateral geniculate body, and optic radiations to the primary visual cortex.
4) The layers and connections of the primary visual cortex and properties of simple, complex and hypercomplex cells in the visual cortex.
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visual pathway
The visual pathway begins when light enters the eye and strikes the retina. Optic nerve fibers carry the visual information from the retina to the optic chiasm, where fibers from the nasal retina cross over. The fibers then continue along the optic tracts to the lateral geniculate bodies before projecting to the primary visual cortex via the optic radiations. The primary visual cortex is located in the occipital lobe.
Physiology retina
The retinal pigment epithelium (RPE) performs several important functions to support photoreceptor cells in the retina. It acts as a barrier between the retina and choroid, transports nutrients between the retina and blood vessels, regulates the subretinal space ion concentration, engages in the visual cycle to regenerate photopigments, and phagocytoses shed photoreceptor outer segments. Phototransduction is the process where photons are converted to electrical signals in the photoreceptor cells. It involves photoisomerization of rhodopsin triggering a biochemical cascade that modulates cyclic GMP levels and closes cation channels, ultimately leading to hyperpolarization.
Embryology of the human eye
The development of the human eye begins around day 22 of gestation as the optic vesicle forms laterally from the prosencephalon. The optic vesicle invaginates and contacts the overlying surface ectoderm to form the lens placode. By day 33, the lens vesicle separates from the surface ectoderm. The optic vesicle then forms the double-layered optic cup, with the lens vesicle embedded within. Various ocular structures develop from the optic cup, surface ectoderm, and surrounding mesenchyme including the retina, lens, cornea, iris, ciliary body, and more. The development of the eye is complete by birth.
Light and Dark Adaptation
This document discusses light and dark adaptation in the eye. It describes how the eye adjusts to bright light through light adaptation over 1-10 minutes as cones take over from rods. Dark adaptation is the eye's ability to recover sensitivity in low light after exposure to bright light, which can take rods up to 30-35 minutes. The mechanisms that allow vision over a wide range of light levels include pupil changes, rods and cones in the duplex retina, dark adaptation, and light adaptation of the visual system. Dark adaptometry is used clinically to diagnose retinal disorders by measuring dark adaptation recovery curves.
Light and dark adaptation chinnu
This document discusses light and dark adaptation in the visual system. It describes the roles of rods and cones in scotopic and photopic vision. Dark adaptation allows the visual system to adjust to low light levels and involves both rods and cones, with rods taking longer to recover sensitivity after being bleached. The document outlines the dark adaptation curve and factors that influence it such as pre-adapting light intensity and duration. Light adaptation occurs more quickly and allows the visual system to function across a wide range of background illuminations.
Vision
The document summarizes key aspects of physiology of vision. It discusses how light is captured by the eye and transmitted through the retina, aqueous humor, lens, and vitreous humor to form an image on the retina. It describes accommodation which allows the lens to change curvature for focusing on near and far objects. It also outlines common refractive errors like myopia and hypermetropia and how they are corrected.
visual pathway
The visual pathway/visual system is the part of central nervous system which gives organisms the ability to process visual detail , as well as enabling the formation of several non-image photo response functions.
It detects interprets information from visible light to build a representation of the surrounding environment .
The visual system carries out a number of complex tasks , including the reception of light and the formation of monocular representations; the buildup of a nuclear binocular perception from a pair of two dimensional projections ; the identification and categorization of visual objects ; assessing distances to and between objects and guiding body movements in relation to the objects seen.
Physiology of vision
Vision occurs through a process called phototransduction where light is converted to nerve impulses in the retina. In photoreceptors like rods and cones, light causes changes in the visual pigment rhodopsin which initiates a biochemical cascade leading to hyperpolarization and decreased neurotransmitter release. Ganglion cell signals are transmitted to the brain where visual perception involves the integration of light sense, form sense, contrast sense and color sense provided by trichromatic and opponent process theories of color vision.
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Development of eye
The eyes develop from four sources during the 22nd day of intrauterine life. Optic grooves form on the forebrain which become optic vesicles that induce lens placodes in the surface ectoderm. The vesicles and placodes invaginate to form the optic cup and lens vesicle. The optic cup differentiates into the neural retina while the lens vesicle forms the lens. The surrounding mesenchyme develops into supporting structures like the choroid, sclera, cornea and vitreous body. Key genes like PAX6 and SHH regulate eye development through epithelial-mesenchymal interactions between the optic cup and surrounding tissues. Abnormalities can result in conditions like coloboma, catar
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2. The middle coat is the vascular tunic, also called the uvea. It contains the choroid, ciliary body, and iris. The choroid supplies blood vessels and nutrients to the eye, while the ciliary body anchors the lens and controls accommodation.
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1. Anatomy of the eye including layers, muscles, and humors.
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The retina contains rods and cones that contain photosensitive proteins like rhodopsin. Rods are for night vision while cones are for day and color vision. The fovea contains only cones for high visual acuity. Phototransduction occurs when light exposure causes rhodopsin to decompose, initiating a signaling cascade that leads to hyperpolarization of the cell. The retina adapts to different light levels through dark and light adaptation. Color vision results from three types of cones sensitive to different wavelengths. Ganglion cells transmit signals from the retina to the brain.
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The document provides information on the anatomy, physiology, and diseases of the lens. It discusses the lens's biconvex shape and ability to change shape to accommodate. The lens is divided into an anterior and posterior epithelium, cortex, and nucleus. It maintains transparency through organized fiber structure, hydration, and antioxidants. The lens focuses light and accommodates through changes in shape mediated by the ciliary body and zonules. Aging and various diseases can impact the lens's structure and function.
Colour vision
This document provides an overview of color vision, including:
- The mechanisms of color vision are based on cones in the retina that detect different wavelengths of light.
- Theories of color vision include Young-Helmholtz trichromatic theory involving red, green and blue cones, and Hering's opponent process theory involving blue-yellow and red-green opponent pairs.
- Color blindness is classified according to which cone is deficient, and can be tested using Ishihara plates or wool tests. Normal color vision is important for occupations like piloting that rely on color coding.
Photochemistry of vision
1. Photochemistry of vision involves photopic, scotopic, and mesopic vision depending on light levels and activation of rods versus cones.
2. Visual pigments such as rhodopsin and cone pigments absorb photons and undergo changes initiating the phototransduction cascade.
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The document summarizes key aspects of physiology of vision. It discusses how light is captured by the eye and transmitted through the retina, aqueous humor, lens, and vitreous humor to form an image on the retina. It describes accommodation which allows the lens to change curvature for focusing on near and far objects. It also outlines common refractive errors like myopia and hypermetropia and how they are corrected.
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It detects interprets information from visible light to build a representation of the surrounding environment .
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The visual pathway begins in the retina and passes through the optic nerves, optic chiasm, optic tracts, lateral geniculate nucleus, optic radiations, and terminates in the occipital lobe. Lesions along this pathway can cause various visual field defects including hemianopias and quadrantanopias depending on the location of the lesion. Lesions in the optic nerve cause blindness on the affected side while lesions in the optic chiasm or tracts cause incongruous homonymous hemianopias. Lesions of the optic radiations or visual cortex cause congruous homonymous defects.
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2. The middle coat is the vascular tunic, also called the uvea. It contains the choroid, ciliary body, and iris. The choroid supplies blood vessels and nutrients to the eye, while the ciliary body anchors the lens and controls accommodation.
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The document summarizes key aspects of vision physiology including:
1. Anatomy of the eye including layers, muscles, and humors.
2. Optics of vision including image formation, accommodation, and optical defects.
3. Visual pathways from the retina through the lateral geniculate nucleus and optic radiations to the primary visual cortex.
4. Photoreceptors including rods and cones and their role in signal transduction.
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Colour vision
This document provides an overview of color vision, including:
- The mechanisms of color vision are based on cones in the retina that detect different wavelengths of light.
- Theories of color vision include Young-Helmholtz trichromatic theory involving red, green and blue cones, and Hering's opponent process theory involving blue-yellow and red-green opponent pairs.
- Color blindness is classified according to which cone is deficient, and can be tested using Ishihara plates or wool tests. Normal color vision is important for occupations like piloting that rely on color coding.
Photochemistry of vision
1. Photochemistry of vision involves photopic, scotopic, and mesopic vision depending on light levels and activation of rods versus cones.
2. Visual pigments such as rhodopsin and cone pigments absorb photons and undergo changes initiating the phototransduction cascade.
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