Lecture Fourteen

• Two roles of gustation:

  • Evaluating the nutritional content of food
  • Preventing the ingestion of toxic compounds
• Five Agreed Concepts of Taste:

  • Sweet
  • Bitter
  • Sour
  • Salty
  • Umami
• Drosophila Taste Sensillum:

  • Have four chemoreceptors and one mechanoreceptor
  • Water cells
  • Sugar cells
  • Salt cells
  • Deterrent cells (Bitter)
  • Taste sensillum have a hole at the end that allows chemicals to enter
  • Found on legs and nose
• Taste Buds:

  • Tongue papillae contain taste buds
  • They do not rest on the surface of the tongue
  • Three types of taste buds:
  • Fungiform papillae: Located at the front of the tongue
  • Foliate papillae: Located on the side of the tongue near the back
  • Circumvallate papillae: Large taste buds at the back of the tongue
  • Each taste bud has 50-150 cells of 4 types
  • Receptors turn over in 5-10 days
  • Type I, II, III
  • Type IV basal cells become new taste receptors
  • Taste receptor cells have microvilli at the taste pore opening
• Taste Receptors:

  • Type I cells: function unknown
  • Type II cells: different variants for sweet, umami, and bitter
  • Type III: most likely used for sour
• Central Representation:

  • Afferents travel in the facial (VII), glossopharyngeal (IX), and vagus (X) nerves to the nucleus of the solitary tract in the brainstem