Taste and Smell

The receptors for taste and smell respond to molecules that are dissolved in fluid; hence, they are classified as chemoreceptors. Although there are only four basic modalities of taste, they combine in various ways and are influenced by the sense of smell, thus permitting a wide variety of different sensory experiences.

Chemoreceptors that respond to chemical changes in the internal environment are called interoceptors; those that respond to chemical changes in the external environment are exteroceptors. Included in the latter category are taste (gustatory) receptors, which respond to chemicals dissolved in food or drink, and smell (olfactory) receptors, which respond to gaseous molecules in the air. This distinction is somewhat arbitrary, however, because odorant molecules in air must first dissolve in fluid within the olfactory mucosa before the sense of smell can be stimulated. Also, the sense of olfaction strongly influences the sense of taste, as can easily be verified by eating an onion (or almost anything else) with the nostrils pinched together.

Tongue surface

Taste pore

Tongue surface

Taste pore

Sensory Nerve Taste Bud

Taste hair

Gustatory (taste) cell

Supporting cell

Sensory nerve fiber

Taste hair

Gustatory (taste) cell

Supporting cell

Sensory nerve fiber

■ Figure 10.7 A taste bud. Chemicals dissolved in the fluid at the pore bind to receptor proteins in the microvilli of the sensory cells. This ultimately leads to the release of neurotransmitter, which activates the associated sensory neuron.

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Responses

  • jamila tesfalem
    Where is the sensory nerve fiber on the tongue?
    8 years ago
  • JESSAMINE
    What is the physiology of olfaction steps?
    8 years ago
  • alfio marino
    Why are taste and smell receptors classified as chemoreceptors?
    8 years ago

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