Transcript The Chemical Senses

The Chemical Senses
Gustatory
All have Chemoreceptors

In order for a sensation to be registered
by the individual … the chemical (aroma
or taste sensation) must be dissolved in
solution.
• Mucus
• Saliva
Gustatory Pathway

Most all taste receptors are located on
the tongue in raised structures called
Papillae
Gustatory Pathway

There are a few
receptors in the
lining of the cheek
and soft pallet
Gustatory Pathway

Epithelial supporting cells forming the
taste bud have microvilli called Gustatory
Hairs connected directly to dendrites

Gustatory cells are shed and replaced
every 7 to 10 days
Gustatory Pathway

The act of tasting evokes reflexes in the
digestive system.
• Increase of saliva production
• Increase of gastric juices release
Gustatory Pathway

The digestive process begins in the mouth
?
Gustatory Pathway

Taste is approximately 80% Olfactory
Gustatory Pathway

The Hot sensation of
peppers excite pain
receptors
Gustatory Pathway

Thermo receptors, mechanoreceptors, and
nociceptors stimulation of these receptor
cites may enhance or detract from the quality
of the sensation
Gustatory Pathway

There are three major types of papillae:
1. Filiform:
no taste buds found
Gustatory Pathway
2. Fungiform:
Mushroom shaped
All over the tongue
Highest concentration
found at the tip and sides
Taste buds are found on the
top of the the papillae
Gustatory Pathway
3. Circumvallates:
Largest and least numerous (7-12) form a “V”
at the back of the tongue
The taste buds are located on the sides of
these papillae
Taste

Many substances produce several
sensations, thus exciting many different
taste buds. Many of the taste buds will
respond to each of the following
qualities.
Taste

Bitter:
• Produced by alkaloids (hydroxide ions)
generally found on the back of the tongue
Taste

Salt:
• Metal ions
• Appears to be evenly distributed
Taste

Sour
• Produced by
hydrogen ions
• Generally found
on the sides of
the tongue
Taste

Sweet:
• Sugars and some amino acids
• Generally found on the tip of the tongue
Gustatory Pathway

Damage to:
• Glossopharyngeal nerve – bitter taste
diminished (Cranial Nerve Number?)
• Facial nerve – sweet, sour, salty taste
diminished (Cranial Nerve Number?)
The Chemical Senses
Olfactory
Olfactory Pathway

Receptors are found on the roof of the
nasal cavity - bilaterally
• There are approximately 5 million olfactory
receptor cells
Olfactory Pathway

Collectively, these receptors are referred to as :
Olfactory epithelium
Olfactory Pathway

Regulation of air flow:
• To reduce the stimulation of receptors:
• Inhale slowly through your nose
• Or inhale through your mouth
• What bone structures allow for the
air being channeled?
Olfactory Pathway

Regulation of air flow:
• To heighten the stimulation of
receptors:
• Inhale quickly through your nose
with your mouth closed
Olfactory Pathway

The sensation of an Aroma is stimulated
by the excitation of olfactory hairs
protruding from the olfactory epithelium
in a field of mucosa manufactured by
glands in the lamina propria
Olfactory Pathway

In order for an aroma to be detected, it
must be volatile
• 1. the aroma must be in
a gaseous state
• 2. the aroma must be water soluble
• Why can we not smell natural gas?
Olfactory Pathway

Acclamation
• A process where the sense of olfaction
adapts quickly
• CNS response is not a diminished
response from the receptor group
Olfactory Pathway
Olfactory neurons are quite different from
other neurons:
they are replaced approximately every
60 days by a process called basal cell
differentiation in the olfactory epithelium
Compare:

Gustatory paths separates four distinct
chemical sensations

Olfactory paths distinguish tens of
thousands of different sensations with
only 15 to 30 different types of receptors
Compare:

The sensation of smell requires the
stimulation of ALL receptors in the nasal
concha prior to detection

The sense of taste?
• Each taste is independent of the other and
does not require the other receptors to be
stimulated
Compare:

The irritating response of strong aromas such as
ammonia stimulates pain receptors
What is the response and why is it important?

Pain receptor stimulation in the mouth provides
us with the sensation of “hot” (spicy).
How do you deal with food that is too
spicy?