Sensory Physiology PPT

• General Classification of Receptors

  • I. Mechanoreceptors
  • II. Photoreceptors
  • III. Chemoreceptors
  • IV. Thermoreceptors
  • V. Nociceptors
  • VI. Electroreceptors
  • VII. Magnetoreceptors
• Receptor Roles


  • Exteroreceptors
  • Interoreceptors
  • Proprioceptors
• Uses for Information Detected by Receptors


  • for control of efferent output
  • for cortical arousal
  • for perception
  • for future reference

  
• Receptor Physiology


  • Receptors may fire continuously or adapt slowly or rapidly to sustained stimulation
• Tonic Receptors


  Muscle stretch receptors, joint proprioceptors
• Phasic Receptors


  Tactile receptors in skin
• Mechanoreceptors in the Integument

  • Pacinian Corpuscle
  • Meissner Corpuscle
  • Ruffini Corpuscle
  • Krause End Bulb
  • Free Nerve Ending
  • Merkel's Cell
• Statocyst


  Proprioceptor that detects motion and position
• Lateral line system


  Proprioceptor that detects fish orientation, swimming velocity, water currents and vibrations

  
• Parts of the Vestibular Apparatus

  • 3 Semicircular Canals
  • Otolith Organs
• Semicircular Canals


  Detect rotational or angular acceleration or deceleration of the head
• Otolith


  Detects position of the head relative to gravity and changes in rate of linear motion
• Mechanoreception of Sound Waves

  1. Sound waves → Body → Otolith (inner ear)

  2. Gas bladder → Weber bone → Inner ear

  3. Action of cilia in sensory cell → Action Potential

  
• Uses of Taste and Smell


  • in association with food intake in some species can influence the flow of digestive juices and affect appetite
  • permit social recognition of kin
  • induces pleasurable or objectionable sensations
  • has a major role in finding direction, finding shelter, seeking prey, avoiding predators, and sexual attraction to a mate
• Tastant


  Molecules in objects in contact with the taste cells
• Pathways of 5 Tastant Categories

  • Salt Taste
  • Sour Taste
  • Sweet Taste
  • Bitter Taste
  • Umami
• Salt Taste


  Stimulated by chemical salts, Na+ → specialized ion channels (regulated by ADH and aldosterone)
• Sour Taste

  Stimulated by acids, H+ blocks K+ channels, Depolarization
• Sweet Taste

  Stimulated by glucose, Glucose + taste cell receptor → activate G-protein → cAMP pathway in the taste cell, Activates IP3 pathway, Phoshorylation → blockage of K+ channels → Depolarization
• Bitter Taste


  Stimulated by alkaloids, Employ various signalling pathways to bring about a receptor potential
• Umami


  Stimulated by amino acid, Glutamate + G-protein coupled receptor → activate a second-messenger system, Details of pathway unknown
• Gustatory Pathway


  Pathway for taste sensation
• Olfactory mucosa


  Where smell sensation occurs, found in the nasal fossae
• Muscle Networks in the Iris

  • Circular
  • Radial
• Light


  Electromagnetic radiation
• Light ray


  Forward movement of a light wave in a particular direction
• Refraction

  Bending of light ray
• Degree of refraction

  The greater the difference in density, the greater the degree of bending, The greater the angle, the greater the refraction
• Accommodation

  The ability to adjust the lens strength in order to focus both near and distant objects
• Refractive Disorders

  • Hyperopia
  • Myopia
• Parts of the Retina

  • Fovea
  • Visual streak
  • Macula lutea
  • Blind spot/Optic disc
• Photoreceptors

  Cells in the retina that convert light energy to neural signals
• Photopigments

  Rhodopsin, Porphyropsin, Scotopsins
• Phototransduction

  Converts light energy to neural signals
• Photoreceptor Activity

  In the Dark
• Dark Adaption

  Adaptation of the eye to low light conditions
• Light Adaptation

  Adaptation of the eye to bright light conditions
• Night Blindness is a clinical correlation related to the visual pathway