1. Three types of Sensory Receptors
   1. exteroceptors
      1. adapted for reception of stimuli from external (out of body)
      2. Ex. Visual, auditory, tactile, olfactory and gustatory
   2. interoceptors
      1. receive info from inside body
      2. Ex. viscera, holow organs and glands such as stomach pain, pinched spinal nerve, or deep skin layer inflammation
   3. proprioceptors
      1. detect body position & movement
      2. located in muscles, tendons, and joints and in utricles, saccules and semicircular canals of inner ear (ex. labyrinths of ear)
2. Developmental Classification of Sensory Receptors
   1. Protopathic
      1. old phylogenetically, adapted to identify gross bodily sensation rather than specific thus cannot precisely locate pain origin. Detect crude touch & dull pain
      2. Evolutionary function: detect possible but not imminent environmental danger
      3. Child with DOMINANT PROTOPATHIC
         1. not able to receive good sensory info from environment or data for CNS is dulled (like wearing heavy coat). May display self-stimulation behaviors (rocking, biting oneself, humming)
   2. Epicritic
      1. recent, Detect with precision, accuracy, acuteness. Discriminative touch, sharp pain, exact joint position, and localization of stimulus
      2. Evolutionary function: allows explore environment w/ precise detail thus about imminent danger
      3. Child with DOMINANT EPICRITIC
         1. hypersensitive to sensation from environment, can be painful or intolerable. Ex. Tactile defensiveness, feel of water hitting the skin during shower is painful. Unable to tolerate movement due to gravitational insecurity
3. Sensory Receptors Classified by Anatomical Location
   1. Cutaneous
      1. respond to pain, temperature, pressure, vibration, and discriminative touch
      2. found: superficial and depp skin layers
      3. Classified: exteroreceptors or interoceptors
   2. Muscle, Tendon, and Joint (proprioceptors)
      1. detect muscle length, tension, joint position, deep muscular and joint pain and tendonitis
      2. found: muscles, tendons and joints
      3. Classified: proprioceptors
   3. Visceral
      1. respond to pressure and pain from internal organs
      2. Classified: interoceptors
   4. Special sense
      1. visual: rods & cones of retina, exteroceptors
      2. olfactory: hair cells in mucous lining of nasal canal, exteroceptors
      3. auditory: hair cells of cochlea, exteroceptors
      4. gustatory: taste buds on tongue, exteroceptors
      5. equilibrium: semicircular canals, utricles and saccules of inner ear, PROPRIOCEPTORS (head position related to body)
4. Sensory Receptors Classified by Structural Design
   1. Mechano
      1. detect touch, pressure, vibration, proprioception, equilibrium and audition
      2. response to mechanical pressure or deformation
      3. ex. hair cells of labyrinth system, skin, stretch skeletal muscles
      4. Types/ detect
         1. Pacinian corpuscles: rapid vibration
         2. Meissner corpuscles: light touch, texture change
         3. Merkel discs: sustained pressure
         4. Ruffini endings: pressure & tension in deep skin layers & fascia
         5. Free nerve endings: touch, pressure and stretch
         6. Baroreceptors: stretch of blood vessels
         7. Ligamentous receptors: ligament stretch & proprioception
   2. Thermo
      1. response to temp change, nociceptors detect harmful temp change
      2. Found: all over external and internal body, Cold receptors: facial skin, tongue, bladder and cornea
   3. Chemo
      1. detect chem stimuli from environment
      2. Types/ stimulation
         1. Direct: immediate contact with chem Ex. taste buds with food
         2. Distance: molecules in gaseous form Ex. scent of baked cookies,
   4. Photo
      1. detect light form environment
      2. Found: retina
      3. Type
         1. Rods: nightime Low light activation, black and white vision in periphery
         2. Cones: daytime, color vision, in fovea (central eye region)
5. Receptor Fields
   1. Def: body area that contains specific types of sensory receptor cells. Becomes activated when stimulated
   2. Location of Small & Large
      1. Small: greatest sensitivity (lips, hands, face, and soles)
      2. Large: less discriminative sensitivity (legs, abdomen, arms, back)
   3. Function of Small & Large
      1. Small: fine discrimination, for environmental exploration
      2. Large: gross discrimination
   4. Homunculus represents cortical
      1. Small: large amount of representation for both sensory and motor bc of sensitivity
      2. Large: smaller