C5 VISUAL SYSTEM

• defined as waves of electromagnetic energy between 380 and 760 nanometers in length

  light
• 2 properties of light

  wavelength

  intensity
• plays an important role in the perception of color

  wavelength
• plays an important role in the perception of brightness

  intensity
• ability to detect the presence of dimly lit objects

  sensitivity
• ability to see the details of objects

  acuity
• regulated donut-shaped bands of contractile tissue

  retina
• give our eyes their characteristic color

  iris
• hole in the iris

  pupil
• greater range of depths is simultaneously kept in focus on the retinas

  depth of focus
• focuses incoming light on the retina

  lens
• tension on the ligaments holding each lens in place

  ciliary muscles
• process of adjusting the configuration of the lenses to bring images into focus on the retina

  accomodation
• difference in the position of the same image on the 2 retinas

  binocular disparity
• 5 different types of neurons in retina

  receptors

  horizontal cells

  bipolar cells

  amacrine cells

  retinal ganglion cells
• communication across the major channels of sensory input

  lateral communication
• bundle of retinal ganglion cell axons to leave the eye, there must be a gap in the receptor layer, this gap is called ___

  blind spot
• indentation about 0.33 centimeter in diameter, at the center of retina, area of the retina that is specialized for high-acuity vision

  fovea
• process by which we perceive surfaces, visual system extracts information about edges and from it infers the appearance of large surfaces


  surface interpolation
• 2 different receptor types in human retina

  cones

  rods
• cone-shaped receptors

  cones
• rod-shaped receptors

  rods
• theory that cones and rods mediate different kinds of vision

  duplexity theory
• cone-mediated vision, predominated in good lighting and provides high-acuity colored perception of the world

  photopic vision
• rod-mediated vision

  scotopic vision
• half of each retina next to the nose

  nasal hemiretina
• half of retina next to the temples

  temporal hemiretina
• graph of the relative brightness of lights of the same intensity presented at different wavelengths

  spectral sensitivity curve
• can be determined by having subjects judge the relative brightness of different wavelengths of light shone on the fovea

  photopic spectral sensitivity curve
• can be determined by asking subjects to judge the relative brightness of different wavelengths of light shone on the periphery of the retina at an intensity too low to activate the few peripheral cones located there

  scotopic spectral sensitivity curve
• an interesting visual effect can be observed during the transition from photopic to scotopic vision

  purkinje effect
• entire area that you can see at a particular moment

  visual field
• eyes continuously move even when we try to keep them still

  involuntary fixational eye movements
• 3 kinds of involuntary fixational eye movements

  tremor

  drifts

  saccades
• small jerky movements or flicks

  saccades
• conversion of one form of energy to another

  transduction
• conversion of light to neural signals by the visual receptors

  visual transduction
• any substance that absorbs light

  pigment
• pigment exposed to continuous intense light, bleached and lost its ability to absorb light

  rhodopsin
• G-protein-coupled receptor that responds to light rather than to neurotransmitter molecules

  rhodopsin