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PHYS 215 (11)
Lecture 10

PHYS 215 Lecture 10: Vision

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Ball State University
PHYS 215
Kelly Worden

1. Vision  Control of light o Iris  Pigmented region of the eye  Anaridia o Pupil  Circular muscle  Smaller  Radial muscle  Dilation  ANS control  Eye anatomy o Retina – innermost layer of the eye that contains the photoreceptors and neuron cells o Choroid – layer beneath the sclera that helps supply blood to the retina o Optic disk – blind spot where the optic nerve exits the eye o Fovea – the area of the retina with highest density of cones (color vision) within the macula luteal o Lens – transparent, biconvex structure of the eye that focuses light rays entering through the pupil to form an image on the retina o Cornea – transparent layer of fibrous connective tissue that with the lens refracts and focuses light rays o Ciliary body – muscles controlling the shape of the lens continuous with and beneath the iris  Light properties o Photons o Wavelength o Visible light  400 – 700 nm o Intensity o Ray  Refraction and accommodation o Refraction  Bending of a light ray o Concave o Convex o Cornea and lens o Accommodation  Increasing the strength (shape) of the lens (near visions)  Ciliary muscle  Visual problems o Myopia – nearsighted o Hyperopia – farsighted o Presbyopia – age related farsightedness o Astigmatism  Photoreceptors o Rods – night vision o Cones – day vision o Bipolar cells – synapse with rods and cones o Ganglion cells –receive input from bipolar cells, axons for the optic nerve o Rod signals travels from bipolar cells, through amacrine cells to ganglion cells  Phototransduction is the conversion of light stimuli into neural signals o Photoreceptor  Three parts: outer segment, an inner segment, and a synaptic terminal o Rhodopsin  Rods  Sodium channels  Open in the absence of light o Three photopigments  Red, green, and blue  Selective to wavelengths  Cones  C
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