6 Vision - Chapter 6 Vision The Stimulus Sensory...

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Chapter 6 Vision
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The Stimulus Sensory Transduction Light enters the eyes and affects sensory receptors Electrochemical signals sent back to the visual cortex Visible electromagnetic radiation for humans is between 380-760 nm
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The Stimulus Visible light is affected by three factors Hue (wavelength) Saturation (purity of light source) Brightness (amplitude)
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Anatomy of the Visual System Eyes Held in their orbits by muscle Connected to 4 cranial nerves (CN) CN 2. Optic Nerve: visual sensation CN 3. Oculomotor Nerve: ciliary muscle and most other muscles CN 4. Trochlear Nerve: oblique muscle CN 6. Abducens Nerve: Rectus lateralis muscle
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Anatomy of the Visual System Muscles of the eye are attached to the sclera Tough, white outer coat of the eye The conjunctiva fences off the outside with the inside of the orbital socket This stops you from seeing the eye muscles
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Anatomy of the Visual System
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Anatomy of the Visual System Eyes make 3 types of movements Vergence movements Keep the image on the proper location of the retina Saccadic movements Start-stop movements Pursuit movements Tracking a moving object The only thing that slows down the saccadic movements
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Anatomy of the Visual System Accommodation The process by which the ciliary muscles focus the lens Retina The retina contains the photoreceptors Humans have 120 million rods and 6 million cones Fovea Filled with cones only Looking directly at an object in low light may make it disappear from view
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Anatomy of the Visual System Blind Spot Also known as the optic disk
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Anatomy of the Visual System The retina has three layers of cells Ganglion cell layer (anterior) Bipolar cell layer Photoreceptor cell layer (caudal) There are a total of 55 cell types in the primate retina From light to action potential, the signal turns a circuitous route
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Anatomy of the Visual System
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Anatomy of the Visual System Photoreceptors The parts needed to convert light into a neural signal are: Lamellae (disks in the photoreceptor) Photopigments Opsin (protein), retinal (vitamin A) Rhodopsin breaks into rod opsin and retinal after being hit by light
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Anatomy of the Visual System
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Anatomy of the Visual System Normally open Ca2+ channels are closed when light is detected Retinal transducin Phosphodiesterase Cyclic GMP Closed ion channel When light is detected, it hyperpolarizes the photoreceptor, which therefore depolarizes the bipolar cell Normally the cyclic GMP receptor is open and that causes the bipolar cell to be hyperpolarized
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Anatomy of the Visual System
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The Six Steps of Converting Light into a Neural Signal in a Rod 1. Light strikes rhodopsin 2. Rhodopsin releases retinal 3. Retinal activates transducin (2 nd messenger) 4. Transducin activates phosphodiesterase
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This note was uploaded on 04/20/2011 for the course PSYCH 3053 taught by Professor Hubertz during the Spring '11 term at FAU.

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6 Vision - Chapter 6 Vision The Stimulus Sensory...

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