Chemical Senses

• How is smell defined according to Kushner (1993)?

  Smell is made up of the molecules of what you're smelling.
• What is the neurogenesis time frame for taste and smell receptors?

  1-2 weeks for taste receptors and 5-7 weeks for smell receptors.
• What are the importance and functions of taste and smell?

  • Prepare the body for digestion
  • Serve as a "gatekeeper"
  • Contribute to the "flavour" of food
  • Strongly connected to memory
• What is the gatekeeper function of taste?

  It identifies what the body needs for survival and detects substances that are damaging to the body.
• What are the four basic tastes and their associated substances?

  • Salty: sodium chloride
  • Sour: hydrochloric acid
  • Sweet: sucrose
  • Bitter: quinine
  • Umami: associated with monosodium glutamate (MSG)
• What are the types of papillae found on the tongue and their characteristics?

  • Filiform: cone shape, no taste buds
  • Fungiform: mushroom shape, contains taste buds
  • Foliate: folds, contains taste buds
  • Circumvilliate: flat-mounds shape, contains taste buds
• How many taste cells does each taste bud contain?

  Each taste bud contains 50-100 taste cells.
• What is the central pathway for taste?

  The central pathway for taste includes the frontal operculum.
• Where does transduction occur in the taste system?

  Transduction occurs at the taste receptors.
• What are the primary taste cortical areas?

  The insula and the frontal operculum, combined as the gustatory cortex.
• How do humans differ from many animals in terms of olfaction?

  Humans are microsmatic, meaning smell is not crucial to survival, while many animals are macrosmatic with a good sense of smell important for survival.
• Why is it difficult to describe smells compared to other senses?

  We lack many words to describe smells, and similar molecules can smell very different while different molecules can smell very similar.
• What is the detection threshold for T-butyl mercaptan?

  0.3 parts per billion.
• What is the role of olfactory receptors in the olfactory bulb?

  Each olfactory receptor is specific to a narrow range of chemicals, and signals are transmitted to the glomerulus.
• What is the chemotopic map in the olfactory bulb?

  The chemotopic map represents different features of molecules by different regions on the olfactory bulb, with longer carbon chains activating receptors further left.
• What are the brain pathways for olfactory signals?

  Olfactory signals travel from the olfactory bulb to the piriform cortex, orbitofrontal cortex, and amygdala.
• What is the role of the piriform cortex in odour perception?

  The piriform cortex participates in the formation of odour objects through a process of pattern completion.
• How is flavour defined and what are its components?

  • Flavour = Taste + Smell
  • Retronasal olfaction: Odorant molecules in the oral cavity reaching olfactory mucosa
  • Orthonasal olfaction: Odorant molecules via the nose
• How do taste and olfaction interact with other senses in the brain?

  Taste and olfaction areas in the brain interact with vision, touch, and sounds to enhance flavour perception.
• What is the orbitofrontal cortex's role in flavour processing?

  The orbitofrontal cortex is the first area where smell and taste signals meet.
• What are bimodal neurons in the orbitofrontal cortex?

  Bimodal neurons respond to more than one sense, such as taste and smell or taste and vision.
• How do congruent colours affect taste perception?

  Congruent colours can enhance taste, such as red enhancing the sweetness of strawberry-flavoured beverages.
• What is the significance of Proust's madeleine in relation to memory?

  • Taste and smell are more enduring and persistent than other senses.
  • They evoke memories and emotions associated with past experiences.
• How do odour-cued memories compare to other types of memories?

  Odour-cued memories are older and often evoke feelings of being brought back in time compared to word-cued or picture-cued memories.
• What is the relationship between smell and memory in the brain?

  Signals related to smell spread to brain areas involved in memory and emotion, such as the hippocampus and amygdala.