1. 3 types of papillae
    • circumvallate
    • fungiform
    • foliate
  2. describe structure of taste bud
    • taste pore at top
    • receptor cell in middle
    • surrounded by supporting cells ('glial like')
    • basal cells at bottom dividing to create new receptor cells
    • synapse at bottom
  3. CN output of taste
    • glossopharyngeal
    • chorda tympani
    • superior laryngeal, from hypoglossal (on epitglottis)
  4. 3 categories of taste cells
    • receptor cells: narrow specificity, 2nd messenger: sweet, bitter, umami
    • presynaptic cells: sour
    • glial-like cells: K and transmitter homeostasis; salt
  5. where is first synapse in processing of taste?
    Within taste bud
  6. Describe different types of receptor cells
    • Umami: T1R1 and T1R3
    • Sweet: T1R2 and T1R3
    • Bitter: ~30 T2R
    • all heterodimeric, GPCR, 2nd messenger coupled
  7. describe transduction within receptor cells
    • GPCR
    • IP3 activated by beta-gamma unit
    • Ca release from intracellular stores
    • and opening of TRP5M cation channels
    • depolarisation
    • transmitter release (ATP) via gap junction hemichannels
  8. describe sour taste processing. Which cells?
    • Presynaptic cells
    • protons cause K channels to close, leading to depolarisation
    • Ca channel opening
    • graded depending on strength of acid
    • depolarisation causes vesicular serotonin release
  9. describe salt taste processing. Which cells?
    • Glial cells
    • ions enter directly through epithelial sodium leak channels
    • protons can also enter through these channels
  10. Difference between transmission from receptor cells and presynaptic cells
    • receptor: gap junction hemichannels (ATP)
    • presynaptic: vesicular serotonin
  11. first synapse of taste CNs
    nucleus of solitary tract of medulla in gustatory nucleus
  12. describe higher taste pathways
    • gustatory NST ? VPM nu of thalamus ? gustatory neocortex (in anterior insula) and frontal operculum
    • primary taste cortex ? orbitofrontal cortex (2ry taste area; pleasantness), amygdala (affective component), lateral hypothalamus (feeding behaviour)
  13. difference with higher taste pathways in lower mammals
    thalamocortical pathway has a pontine relay in parabrachial nucleus
  14. describe sensory coding in taste
    • 'across line'
    • different nerves respond to all different tastes, but in varying proportions
    • need to compare response
  15. 2 inputs to afferent smell fibres
    • ATP through gap junction hemichannels from receptor cells
    • serotonin from presynaptic cells (these themselves receive purinergic input)
Card Set
NHB taste