The senses, basic principles

• Vision


  electromagnetic radiation (wavelengths)
• Audition


  air pressure (wavelengths)
• olfaction


  volatile chemical molecules
• Taste


  non-volatile chemical molecules
• Vestibular


  movement of the head
• selectivity of visible light


  -energy= electromagnetic radtion

  -400-750 nanometers (~10^7 m)
• selectivity of pressure


  -energy = air pressure changes

  -20-20,000 Hz (cycles/sec)
• selectivity of taste


  -Energy= non-votile chemicals

  -5 tastes-chemical structures
• selectivity of smell


  -energy = Volatile chemicals

  -350+-unique chemical structures
• Minimal detectable intensity is influenced by


  context, motivation, expectations, attention, species specific
• sensation is an active process to

  capture the energy, transduction, extraction of feature, reconstruction of whole
• sensory organ for vison

  retina
• sensory receptor for vision

  photoreceptors (rods and cones)
• sensory organ for audition

  cochlea
• sensory receptor for audition

  hair cells
• sensory organ for taste


  taste buds and tongue
• sensory receptors for taste


  taste receptors cells
• sensory organ for olfaction

  nose
• sensory receptor for olfaction

  chemoreceptors, olfactory receptor cells
• sensory organ for kinesthetic

  joints/muscle
• sensory receptor for kinesthetic


  Neurons (proprioreceptors)
• sensory organ for vestibular


  otolith organ (semi-circular canals) attached to the cochlea
• sensory receptors for vestibular

  hair cells
• what captures the energy?

  sensory organs
• what transduces the energy?

  sensory receptors
• Transduction


  -a process by which energy is changed to another energy.

  -physical energy change to neural energy (graded potentials)

  -"generator potential"
• photopic system receptor


  cones
• scotopic system receptor


  rods
• number of receptors per eye for photopic system

  4 million
• number of receptors per eye for scotopic system

  100 million
• photopic system photopigments


  three classes of cone opsin; the basis of color vision
• scotopic system photopigments


  rhodopsin
• sensitivity of photopic system


  Low; needs relatively strong stimulation; used for day vision
• Sensitivity of scotopic system


  High; can be stimulated by weak light intensity; used for night vision
• location of photopic system in retina

  concentrated in and near fovea; present less densely throughout the retina
• location of scotopic system in retina

  outside fovea
• receptive-field size and visual activity of photopic system


  small in fovea, so acuity is high; larger outside fovea
• receptive-field size and visual activity of scotopic system

  lager, so acuity is lower
• photopic system response time

  rapid
• scotopic system response time

  slow