Taste

• What are the 3 types of taste papillae?

  Fungiform, circumvallate, foliate
• What are the 5 principle tastes?

  Bitter -> 2X – 25 T2Rs

  Salty -> Na+

  Sweet -> T1R2 & T1R3

  Unami -> T1R1 & T1R3

  Sour -> H+
• Why do we have so many receptors for bitter (25 T2Rs)?

  Detection of potentially harmful substances.

  -> poisonous things are usually bitter
• Fill in the blanks

  A) Circumvallate

  B) Foliate

  C) Fungiform

  
• Taste buds are comprmised of 4 principle cell types, what are these?

  Type I - 'glial-like' cells

  Type II - receptor for bitter, umami, sweet & salty

  Type III - receptor for sour

  Type IV - located basally, act as progenitor cells
• What are the 3 cranial nerves that innervate the tongue & where do they innervate?

  Facial nerve -> anterior 2/3 of tongue

  Glossopharyngeal nerve -> posterior 1/3 of tongue

  Vagus nerve -> back of larynx & epiglottis
• There is no evidence of a cortical map for taste.
• Taste

  Taste receptor detects its specific taste -> activates signalling cascade (depends on the taste & the receptor) -> release of ATP (type II cell) or serotonin (type III cell) -> AP generated -> signal travels along cranial nerve (which one depends on the location of the taste perceive on the tongue) -> projects to solitary nucleus ipsilaterally (in medulla) -> neurons project to ventral posterior medial nucleus of the thalamus AND parts of limbic system (amygdala) -> thalamicortical neurons projects to gustatory cortex (in insular lobe)