Chapter 1 People Gustav Fechner Ernst Weber o Weber s law Joseph Fourier Johannes Muller o Thought by some to be the founder of experimental psychology o Invented psychophysics o Fechner s law o Struggled with the mind body problem o Discovered the smallest detectable change in a stimulus is a constant proportion of the stimulus level o Fourier Analysis any complex sound can be broken down into individual sine wave components through this process o Formulated the doctrine of specific nerve energies o Discovered its more important which nerves are stimulated not how they are stimulated Hermann Ludwig Ferdinand von Helmholtz o Thought behavior should be explained by only physical forces o First person to measure the speed of neural impulses o Demonstrated that neurons follow the laws of physics o Invented the ophthalmoscope Santiago Ramon y Cajal o Known for his artistry detailed drawing o Discovered the direction of travel of nerve impulses Chapter Two Definitions Light visible light Electromagnetic radiation that can be conceptualized as a wave or a Wave Oscillation that travels through medium by transferring energy from one particle stream of photons or point to another Photon a quantum of visible light or other electromagnetic radiation demonstrating both particle and wave properties Particle Something with mass and energy Absorbed Energy e g light that is taken up and not transmitted i e it is transformed into different form of potential or kinetic energy Scattered Energy that is dispersed in an irregular fashion i e randomly When light enters the atmosphere much of it is absorbed or scattered and never reaches our eyes Reflected Energy that is redirected when it strikes a surface Transmitted Energy that is passed on through a surface when it is neither reflected nor absorbed by the surface Refracted Energy that is altered as it passes into another medium e g light entering water from the air or a lens system e g the eye Index of Refraction Indicates how much light bends when it goes from one medium to another o Responsible for image formation and rainbows Cornea The front part of the eye a transparent window into the eyeball Aqueous Humor The watery fluid in the anterior chamber between cornea and lens o Provides oxygen nutrients and o Removes waste from cornea lens Crystalline Lens The lens inside the eye which allows changing focus Pupil The circular opening aperture at the center of the iris in the eye where light Accommodation enters the eye Iris The colored part of the eye between the sclera white part and the pupil consisting of a muscular diaphragm surrounding the pupil and regulating the light entering the eye by expanding and contracting the pupil Vitreous Humor The transparent fluid that fills the large vitreous chamber in the posterior part of the eye i e between the lens and the retina o Where floaters occur Retina A light sensitive membrane in the back of the eye that contains rods and cones and other neurons supporting vessels and structures which receives an image from the lens and sends it to the brain through the optic nerve Accommodation change in focus The process in which the lens shape is changed by the ciliary muscle thus altering its refractive power Emmetropia No refractive error no need for corrective eyewear Diopter unit of measurement of the optical power of a lens or curved mirror Reciprocal of focal length in meters D 1 f m Myopia When light entering the eye is focused in front of the retina and distant objects cannot be seen sharply nearsightedness Hyperopia When light entering the eye is focused behind the retina farsightedness Presbiopia old sight Hardening of the crystalline lens The lens becomes sclerotic harder and the capsule that encircles the lens enabling it to change shape loses its elasticity Astigmatism A visual defect caused by the unequal curving of one or more of the refractive surfaces of the eye usually the cornea requiring cylinder correction Photoreceptors Cells in the retina that initially transduce light energy into neural energy color reflective Rods Photoreceptors that are specialized for night vision o Respond well in low luminance conditions o Do not process color Cones Photoreceptors that are specialized for daylight vision fine visual acuity and o Respond best in high luminance conditions Duplex Retina retina with cones and rods for day and night vision Pigment Epithelium Provides nutrients to photoreceptors Usually opaque sometimes Photoreceptors Rods dim light larger more numerous more sensitive not in fovea Cones better acuity daylight mostly in fovea few in periphery usu 3 types S M L Horizontal Cells located between photoreceptors and bipolar cells Perform lateral inhibition Responsible for center surround receptive fields Bipolar Cells bridge between photoreceptors and ganglion cells Two types midget 1 1 cone ganglion giving low convergence and diffuse connected to several photoreceptors giving high convergence Amacrine Cells less well understood Seem to integrate information from groups of bipolar cells and communicate to ganglion cells Ganglion Cells Connection between eye and brain Recieves information from bipolar cells and amacrine cells and sends info via the optic nerve Age related Macular Degeneration AMD A disease associated with aging that affects the macula AMD gradually destroys sharp central vision Macula The central part of the retina containing the fovea Scotoma AMD causes central vision loss resulting in a blind spot in this visual field Wet AMD Abnormal blood vessels grow under the macula and can leak blood and fluid raising the macula and impairing central vision As the macula is displaced straight lines may look wavy Dry AMD More common Occurs when macula cones degenerate Sometimes dry AMD turns into wet AMD Once dry AMD is advanced no treatment can reverse the loss of vision Horizontal cells Specialized retinal cells that run perpendicular to the photoreceptors and make contact with photoreceptors and bipolar cells o Responsible for lateral inhibition which creates the center surround receptive field structure of retinal ganglion cells Amacrine cells These cells synapse horizontally between bipolar cells and retinal ganglion cells Horizontal Pathway Horizontal cells amacrine cells Bipolar cell A retinal cell that synapses with one or more rods or cones not both and with horizontal cells and then passes the signals on to ganglion cells o Diffuse bipolar cell A bipolar cell that receives input