Chapter 16: Chemical Senses

• Olfaction = smelling
  • Receptors regenerate every 5-7 weeks
• Molecule detectors = Taste
  • Regenerate every 1-2 weeks
• Relevant because….. Covid, or when you scald your tongue, chemo destroys rapidly generating neurons like taste receptors

Taste

• Goes from the stimulation of receptors on the tongue

Function of Taste

• To decide what to and what not to eat (tells us what is good and not good, helps us to detect things we should not eat)
  • Sweetness causes an automatic acceptance
  • Bitterness causes an automatic rejection (poison is bitter)
  • Genetic and cultural components involved (ex/ Duran you eat right before it goes bad)
  • We adjust to bitterness by combining it with sweet
• 4 (maybe 5) different archetypes of taste - most of what we taste are mixtures of these
  • Salty
  • Sour
  • Sweet
  • Bitter
  • Umami (meaty kind of MSG taste)
  • Each one of these have specific receptors on the tongue for that type of taste
• Taste and learning: taste is a powerful cue for learning
  • Taste aversion learning: taste something novel and then wait to see if they get sick before eating more than a little of it
  • Rats can’t vomit but they can dry heave - foods they dislike they will avoid at all costs

Structure of taste

• Starts at tongue
• Which contain papillae where the taste buds are (100k)
  • Mostly on the periphery of the tongue
  • Each taste bud has about 50-100 taste cells
  • Transduction is chemicals contacting these receptors generating graded potentials which can lead to action potentials
  • Nerves then enter the brain via the nucleus of the solitary tract
  • Thalamus
  • Insula and from operculum cortex (Figure 16.5)
  • The insula brain region is fundamental for a lot of cortical functions
  • The smell also involves the insula
• Taste = activity of different neurons (selective and nondiscriminatory neurons)

Taste is…

• Due to both selective firing of neurons and distributed firing of a variety of neurons