Gustation and Olfaction
The Senses of Taste and Smell
Why do we study taste and smell
SENSORY INTERACTION: the principle that one
sense may influence another.
The senses of taste and smell have a very
cooperative working relationship.
Many of the subtle distinctions you may
think of as flavors really come from odors
 Often, if you can’t smell the food, you can’t
taste the food.
Gustation – The Sense of Taste
What is the central muscle involved in
Five Distinct Tastes:
Five Distinct Tastes:
Umami: the taste of glutamate (MSG) – savory taste
in meat and cheese
Five Distinct Tastes:
Five Distinct Tastes:
Each of these tastes developed as survival
functions, according to evolutionary
Sweet - energy source
Sour – potentially toxic acid
Bitter – potential poisons
Salty – sodium essential to physiological
Umami – proteins to grow and repair tissue
A Theory Debunked
Since 1942, tongue maps like this one were
widely published and touted as an accurate
portrayal of where certain taste receptors
were located.
Wine glasses are even designed around this idea.
The notion that the tongue is mapped into
four areas—sweet, sour, salty and bitter—is
wrong. There are five basic tastes
identified so far, and the entire tongue
can sense all of these tastes more or less
The tongue map is easy enough to prove
wrong at home.
Place salt on the tip of your tongue. You'll
taste salt.
For reasons unknown, scientists never
bothered to dispute this inconvenient
truth until 1974, and even today, many
textbooks still publish pictures of the
tongue map.
Remarkably, more is known about vision
and hearing, far more complicated senses,
than taste.
Those bumps on our tongue
are called papillae.
Papillae help grip food while
your teeth are chewing. They
also have another special job
They contain your ___________
Each has 200 or more taste
Individuals vary in their
sensitivity to taste sensations,
a function of the density of
these papillae on the tongue.
Taste Buds
Each taste bud contains a pore
that catches food _____________
Each taste bud pore has 50-100
taste receptor cells with antenna
like hairs that sense food
Figure 4.49: The tongue and taste.
(a) Taste buds line the trenches around tiny bumps on the tongue called papillae. There
are three types of papillae, which are distributed on the tongue as shown in (b). The
taste buds found in each type of papillae show slightly different sensitivities to the four
basic tastes, as mapped out in the graph at the top. Thus, sensitivity to the primary
tastes varies across the tongue, but these variations are small, and all four primary
tastes can be detected wherever there are taste receptors. (Data adapted from
Bartoshuck 1993a).
Taste receptors reproduce themselves every week or
two (this is why it hardly matters if you burn your tongue
with hot food).
As you grow older, the number of taste buds decreases,
as does taste sensitivity.
As with other senses, your __________
influence your brain’s response.
If you are told something is going to taste bad, your
brain responds more negatively.
Likewise, being told that a wine costs $90 rather than
its real $10 price makes an inexpensive wine taste
better and triggers more activity in a brain area that
responds to pleasant experiences.
As happens with the pain placebo effect, the
brain’s thinking frontal lobes offer information
that other brain regions act upon.
Our Sense of Smell
How Olfaction Works
Smell (Olfaction): operates much like the sense
of taste.
The physical stimuli are chemical substances carried
in the air that are dissolved in fluid, the mucus in the
Pathway: Olfactory cilia -> neural impulse -> olfactory
nerve -> olfactory bulb (Brain)
Olfactory receptors (olfactory cilia) and are located in the upper
portion of the nasal passages.
The olfactory receptors instantly alert brain through axon fibers
the brain.
Olfaction is the only sense that is not routed through the
This suggests that smell ____________ __________ than the
other senses.
How Olfaction Works
Receptor proteins are embedded on the surface
of nasal cavity neurons
As a key slips into a lock  odor molecules slip
into receptors
Some odors trigger a combination of receptors
Odors are not easily classified.
Humans can distinguish among about 10,000 odors,
but for some reason have a hard time attaching
names to odors quite frequently.
Figure 4.51: The olfactory system.
Odor molecules travel through the nasal
passages and stimulate olfactory cilia. An
enlargement of these hairlike olfactory
receptors is shown in the inset. The
olfactory nerves transmit neural impulses
through the olfactory bulb to the brain.
Figure 4.51 The olfactory system
In many animals, the sense of smell is used for
communication. For example, insects such as ants and
termites and vertebrates such as dogs and cats
communicate with each other by secreting and detecting
odorous signals called pheromones – especially to signal
sexual receptivity, danger, territorial boundaries, and food
We humans seem to use the sense of smell primarily in
conjunction with taste to seek and sample food, but some
evidence exists to suggest that people may also use sexual
pheromones as well as pheromones that help us identify
family members by smell.
For more information:
Video on PBS called “Sweaty T-Shirts and Human Mate
Choice” for an evolutionary perspective on pheromones
Fragrance Effects
Research suggests that pleasant scents may trigger pleasant moods
and give a boost to workers’ performance.
Social psychologist Robert Baron, who has studied these fragrance
effects, has patented and is marketing a device that emits pleasant
scents. Called PPS (Personal Productivity/Privacy System) it
combines fragrance release with a whitenoise generator and an air
After testing dozens of smells, Baron found that lemon and light floral
had broad appeal (pine was the least popular odor), and is marketing
discs producing these odors with the PPS.
On a much larger scale, Shimizu Corporation has also patented an
“odordelivery” for commercial buildings. For example, it pumps a
citrus odor through an office building’s ventilation ducts every two
minutes. “The fragrance sense can be fundamental to controlling
conditions for office workers,” says Junichi Yagi, a representative for
Shimizu. He cites a monthlong study of Japanese keypunchers in
which those who inhaled a lemon aroma make 54 percent fewer
errors than those who sniffed plain air. While the citrus odor seemed
to make people more alert, other smells, such as spiced apple,
seemed to aid relaxation.