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Flashcards in L15 Taste and Smell Deck (11):

What did taste and smell primitively act as?

A protective mechanism


now provide pleasure and comfort as well as warning


What functions do smell and taste have?

  • Protective
  • Reproductive function
  • Menstrual cycles of females living together synchronise due to pheromone release


What is the olfactory mucous membrane?

a specialised area of nasal mucosa composed of cells adapted for chemotransduction of odours into electrical signals. 

(yellow in diagram)


Explain the act of sniffing

Normally air flows smoothly past the nasal turbinates, but the act of sniffing makes the flow turbulent and draws air up onto the olfactory membrane.


  1. What supports the receptor cells?
  2. What do the receptor cells have on their surface
  3. How do receptor cells link to the olfactory cortex?
  4. What can explain the link between smell and memories?
  5. What explains how a simple organ with 10000 R cells can sense over 10,000 smells
  6. Discuss human smell

  1. Mucous-secreting sustentacular cells
  2. Cilia
  3. connect via complex intermediate neurons 
  4. The olfactory cortex is part of the limbic system and the frontal lobe
  5. The complex linkage between receptors and cortex 
  6. can recognise over 10,000 separate odours.  Intensity discrimination, however, is not great.  Although one can detect certain odours at very low concentrations, it takes a change in odorant concentration of about 30% before a difference is detected (contrasting with 1% difference in light intensity perceptible).


How many different modalities can the tongue discriminate?


  • Sweet
  • Salty
  • Bitter - particularly sensitive, alerting us to poisons
  • Sour
  • umami (detects glutamate and is pleasant and sweet)


What do each of the 5 modalities  sense?

  1. Bitter - quinine
  2. Sour - H+  Organic acids, HCl etc
  3. Salty - Na, K
  4. Sweet - di- & monosaccharides, some amino-acids, cyclamate
  5. Umami - glutamate (apparently is activated maximally by MSG in asian food)

thought that taste is also added to by irritant and pain receptors to the capsaicin found in chillies and to some substances found in curries


What innervates the tongue?

Chorda tympani N. (VII)

Glossopharyngeal N. (IX)


Hypoglossal N. (XII)


How is taste detected?

chemoreceptor cells with microvilli (gustatory hairs), 40 or 50 of which go to make up a taste bud

the gustatory hairs project through a pore

Binding of the chemical particular for the cell causes release of neurotransmitter from the cell



How is taste sensation carried to the brain?

Carried by two nerves: Chorda tympani N. (VII), Glossopharyngeal N. (IX)

Project to Nucleus of the Tractus Solitarius (NTS) in the medulla oblongata, then travels to the face area of the sensory cortex of the Post Central Gyrus


Sum up taste and smell

Smell and taste are chemoreceptive senses, important for survival and emotional well-being.

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