Lecture 9 for Neurobiology
Lecture 9 for Neurobiology Bil 268
Popular in Neurobiology
Popular in Neurobiology
This 3 page Class Notes was uploaded by Pooja Dave on Thursday September 29, 2016. The Class Notes belongs to Bil 268 at University of Miami taught by Dr. Zhongmin in Fall 2016. Since its upload, it has received 6 views. For similar materials see Neurobiology in Neurobiology at University of Miami.
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Date Created: 09/29/16
Neurobio Lecture 9: Vision I 20/20 = normal vision o 20 ft away from eye chart o numerator = you, denominator = normal people o 20/40 = worse vision than normal people o 20/10 = better vision than normal people, fighter jet pilots o UK: 6/6 m not ft Light o Electromagnetic radiation o Visible light = 400-700nm Energy is proportional to frequency or inversely proportional to wavelength High energy = gamma radiation and cool colors Low energy = radio waves and hot colors o Optics Absorption = Light absorbed by surface, dark Refraction = light bends in source, two different densities The bending makes the perceived distance from object wrong Fish is closer to you than you see it is Reflection = light bounces back The eye o Pupil = light enters to stimulate retina o Iris = color of eye, circular pigmented muscle that contracts or relaxes the size of pupil and controls amount of light that enters eye o Sclera = white part of eye o Conjunctiva = inner surface of eyelid o Cornea = first structure the light hits, covering for eye, provides focusing power o 3 layers of muscles = medial, lateral, oblique o Strabismus = cross eye, misalignment of lateral eye muscle o Amblyopia = lazy eye, hide good eye and let lazy eye do the work when young o Cataract = cloudy lenses o Lens = connected by zonule fibers that connect to ciliary muscle Elasticity = allow for contraction and relaxation, decreases with age ciliary muscle contracts, lens releases, increase curvature Ciliary muscle relax, lens contracts, decreases curvature o Light enters: Hits cornea first Then aqueous humor Pupil then aqueous humor then lens Vitreous humor Retina with receptor cells o Glaucoma = high pressure of aqueous humor that pushes vitreous humor back and harms optic nerve o Retina Left eye = P282 Optic disk = blind spot, no photo receptors Macula = yellowish area Fovea = central area of macula, o Image formation Refraction of cornea = light bends in the cornea allow focusing power Refractive power = 1/focal distance Accommodation of lens Emmetropia = normal Myopia = concave lens for near sightedness, Hyperopia = convex lens for far sightedness Far point = flat lens Near point = fat lens Disease usually caused by elongation of eye ball Retina o Structure Laminar = layer Inside out = layers of cells are backwards 3 cell layer Ganglion cell = first to be hit by light, neurons Bipolar cell = in between ganglion and photo receptor, neurons that do not fire APs (non-spiking neurons) Photo receptor = outer layer of eye, capable of generating AP but not neurons o Rods and cones Light pathways = goes from ganglion to photoreceptor Response pathway = goes from photo receptor where it is converted to chemical signal to ganglion onto the brain o Photoreceptors Rods = works well in dim light situation Cones = works well in bright light situation, color vision Duplex Scotopic = rods, photopic = cones Distribution Fovea = has highest number of cones and almost no rods Blind spot = has no photorecptors Outside of fovea = rods has higher density than cones Rods have many to one ganglion, cones have one to one ganglion Fovea = no rods, has highest visual acuity, pit so that light directly hits the cones o Phototransduction Rods = depolarized without light stimulation, stimulated by light hyperpolarizes membrane cGMP gated Na ion channel = cGMP high in the darkness causing influx of Na in the dark (dark current), channel closed when light stimulated so hyperpolarized rods have rhodopsin that changes configuration and activates GMP to close Na channel when light stimulates it cones 3 types of opsins: RGB o Each color cone has one photopigment – red, blue, green o Sensitive to different wavelengths depending on the color Color vision: young-helmholtz trichromacy theory Dark and light adaptation 20-26 minutes All cone to all rod Factor = dilation of pupils, regeneration of unbleached rhodopsin, adjustment of functional circuitry o Calciums role in light adaption Ca concentration changes in photoreceptors Indirectly regulates levels of cGMP and ion channels Calcium leaks in and reduces cGMP concentration and closes Na channel o