neurobio 913 ch 8 of Bear's book: the chemical senses part 1 (taste umami bitter sweet smell T2

Card Set Information

neurobio 913 ch 8 of Bear's book: the chemical senses part 1 (taste umami bitter sweet smell T2
2014-03-23 14:55:46
neurobio 913 Bear book chemical senses part taste umami bitter sweet smell T2Rs pheromones olfactory epithelium
neurobio 913 ch 8 of Bear's book: the chemical senses part 1 (taste, umami, bitter, sweet, smell, T2Rs, pheromones, olfactory epithelium)
Show Answers:

  1. what is the chemically sensitive part of a taste receptor cell called?
    the apical end
  2. what structures are found on the apical end of the taste receptor cell?
    the apical ends hve thin extensions called microvilli that project into the taste pore, a small opening on the surface of the tongue where the taste cell is exposed to the contents of the mouth
  3. what is a taste bud?
    a taste bud is a cluster of taste receptor cells
  4. on what structure are taste buds anchored to?
    taste buds are located in the "wells" of papillae
  5. what are the three mechanisms by which a tastant can affect a taste cell?
    the tastants may directly pass through ionb channels, bind to and block ion channels, or bind to G protein coupled receptors in the membrane that activate second messengers, that, in turn, open ion channels.
  6. how does the mechanism for detecting salty taste work?
    taste cells for saltiness have Na ion channels that are open all the time. when the concentration of Na increases in the mouth, the Na diffuses into the taste cells and causes depolarization, triggering a receptor potential.
  7. true or false, the anions that are associated with the Na have no effect on salty taste?
    false, the anions of salts affect the taste of the cations.
  8. what is the mechanism for sour taste?
    the H+ ions can go through the amiloride-sensitive Na channels that are responsible for salty taste, and they can bind to K chennals, which blocks the K channels. This results in depolarization.
  9. what similarity do bitter, sweet, and umami receptors have?
    each of these receptors are G-protein coupled receptors. Each of them triggers the same exact second messenger systems.
  10. explain the second messenger pathway of bitter, sweet, and umami cells
    when a tastant binds to one of these cells, it activates G proteins, which stiulate the enzyme phospholipase C, thereby increasing production of the intracellular messenger IP3. The IP3 activates a special type of ion channel depolarizing the cell. This depolarization, n turn, causes calcium channels to open, allowing Ca to flow inside. IP3 can also trigger realease of Ca from intracellular storage sites. These two sources of Ca both help trigger neurotransmitter release, thereby stimulating the gustatory afferent axon.
  11. what are the two proteins subunits that sweet receptors are made up of?
    T1R2 and T1R3
  12. what are the two protein subunits that umami receptors are made up of?
    T1R1 and T1R3
  13. what are the three steps to distinguish the unique flavors of a food?
    • 1. each food activates a diff. combination of taste receptors.
    • 2. has a distinct smell.
    • 3. other sensory modalities (texture, temperature, and pain)
  14. True or false, most papillae tend to be sensitive to only one basic taste when taste stimuli is low, but sensitive to all when stimuli concentration is high
  15. taste receptors are linked to what type of nerves?
    cranial nerves
  16. describe the pathway that info. takes from taste cells to the brain
    The information travels up cranial nerves. The information then enters the gustatory nucleus in the medulla.Neurons of the gustatory nucleus synapse on a subset of small neurons in the ventral posterior medial nucleus, a portion of the thalamus that deals with sensory information from the head. The VPM taste neurons then send axons to the primary gustatory cortex.
  17. why is gustation important?
    It helps us stay away from poisonous substances. It also is important for many basic behaviors such as the control of feeding and digestion.
  18. explain population coding
    population coding refers to the idea that responses from a large number of broadly tuned neurons, rather than a small number of precisely tuned neurons, are used to specify the properties of a particular stimulus, such as taste.
  19. what is responsible for our sense of smell?
    olfactory epithelium
  20. true or false, olfactory cells are not neurons
    false, olfactory cells are neurons, as opposed to taste cells, which are not
  21. what are pheromones?
    chemicals released by the body