Chemical Senses

  1. Key Topics in Chemical Senses:

    • Taste and smell receptors

    • Cortical pathways for taste and smell

    • Flavour perception (combination of taste + smell)

    • Retronasal and orthonasal olfaction

    • Multisensory integration in the orbitofrontal cortex

    • Taste, smell, and memory connection

  2. Taste:

    • Acts as a gatekeeper for survival (detecting harmful or nutritious substances).

    • Basic tastes: salty, sour, sweet, bitter, and umami (savory).

    • Taste system structure involves papillae (e.g., filiform, fungiform) containing taste buds and cells that regenerate every 1-2 weeks.

    • Central pathway: Taste signals travel via specific nerves (e.g., chorda tympani) to the thalamus, then to the insula and frontal operculum (gustatory cortex).

  3. Smell (Olfaction):

    • Humans have a less acute sense of smell (microsmatic) compared to macrosmatic animals.

    • Olfactory system processes odors via receptors in the olfactory mucosa, which send signals to the olfactory bulb and cortical areas like the piriform cortex and amygdala.

    • Smell is linked to memory and emotions.

    • Chemotopic maps in the olfactory bulb represent molecular similarities.

  4. Flavour Perception:

    • Combines taste and smell (via retronasal and orthonasal olfaction).

    • Multisensory interactions (taste, smell, vision, touch) occur in the orbitofrontal cortex, where bimodal neurons process congruent sensory qualities.This integration enhances our overall flavor experience and allows for more complex perceptions of food.