Structures of the tongue involved in the sense of taste • Figure 8.5
Vallate papilla
Fungiform papilla
Palatine tonsil
Lingual tonsil
Papillae are elevations on the
upper surface of tongue on
which taste buds are found.
• Vallate —
• Fungiform
b. Details of
papillae
Taste bud
Gustatory hairs
project from each
gustatory receptor.
Gustatory receptor
senses taste.
Connective tissue -
supports taste bud.
a.
Dorsum of tongue
showing location
of papillae
Taste pore is the
opening in the taste bud.
Stratified
squamous
epithelium
makes up
papilla.
Gustatory sensory neurons
synapse on gustatory
receptors.
Epiglottis
c.
Structure of
a
taste bud
Gustation Involves Receptors from
Both the Oral and Nasal Cavities
Like odors, molecules that are collectively called tastants
bind to taste receptors (gustatory receptors) on the
tongue (Figure 8.5). While we can detect 10,000 differ-
ent odors, we can detect only about five primary tastes:
sour, sweet, bitter, salty, and umami (u-MAM-e). Umami is
described as “meaty” or “savory.” In the gustatory center,
combinations of these five primary tastes and the associ-
ated smells allow detection of hundreds of flavors.
Unlike the nose, the tongue has no “sticky” mucus to
trap tastant molecules. Instead, the tastants dissolve in
saliva, enter taste pores, and contact the hairs of gusta-
tory receptors on the tongue. The gustatory receptors
transmit their information via several cranial nerves
(VII, IX, X; see Figure 7.18) to the primary gustatory
area in the parietal lobe of the cerebrum, the limbic sys-
tem, and the hypothalamus (see Figure 7.10). Because
gustatory information is sent to the limbic system, some
tastes may evoke strong memories. Some memories may
be strong and unpleasant and cause you to avoid certain
tastes (taste aversion); others may evoke more positive
responses, such as reminding you of your mother’s deli-
cious pie.
Individual gustatory receptors may respond to one of
the five primary tastes and may adapt completely to a spe-
cific taste within one to five minutes of continuous stimu-
lation. There is a tendency for the first bite of food to be
more “flavorful” than that last bite on the plate. Different
tastes arise from different patterns of activation of various
taste buds as well as activation of the various olfactory re-
ceptors. In the absence of smell (such as when your nose is
stuffy with a cold), flavors tend to “taste” differently.
CONCEPT CHECK
1.
Which
cells in the olfactory pathway detect
odors?
2.
How
are odorants transformed into neural sig-
nals?
3.
What
structures are involved in detecting a
tastant?
4.
Through
what cranial nerves do nerve impulses
from taste buds pass?
234 CHAPTER 8
Somatic Senses and Special Senses
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