TASTE SENSATION
Dr. Abdelrahman Mustafa
Department of Basic Medical Sciences
Division of Physiology
Faculty of Medicine
Almaarefa Colleges
• Taste is one of the special senses used by
the brain to distinguish certain aspects of
the natural world, and discern poisons and
unhealthy foods, specialized chemical
sense
smell contributes strongly to taste
perception (flavour).
• However, recognition and memory also
plays a role in taste
• TASTE PAPILLAE :small
projections tat distributed
in the tongue
• TASTE BUDES : the
sensors of several types
of the test
• TYPES OF THE TASTE : 5
types
papillae of the tongue
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The taste buds are located in the mucosa of
the epiglottis, palate, and pharynx and in the
walls of papillae of the tongue
The fungiform papillae are rounded
structures most numerous near the tip of the
tongue Each fungiform papilla has up to
five taste buds, mostly located at the top of
the papilla
the circumvallate papillae are
prominent structures arranged in a V shape
on the back of the tongue.
the foliate papillae are on the posterior
edge of the tongue. Each fungiform papilla
has up to five taste buds, mostly located at
the top of the papilla
While each vallate and foliate papilla contain
up to 100 taste buds, mostly located along
the sides of the papillae.
Circumvilliate
Filliform
Folliate
Fungiform
taste buds
• - The specialized sense organ
for taste (gustation) consists of
approximately 10,000 taste
buds, which are ovoid bodies
measuring 50–70 m.
• - There are four
morphologically consist of
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1)Epithilal layer
2)Microvilli
3)sense cell
4)Synapses
5)basal cells
6) Supporting cells
Bitter
Sour
Sweet
Salty
Umami
Taste Pathways
• Taste Pathways:
•
on the anterior 2/3
of the tongue run at
• First in the lingual N
• then join
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chorda tympani
•
branch of the
• facial nerve.
the posterior 1/3
• of the tongue to the
• brainstem via the
• glossopharyngeal N
The fibers from areas
other than the tongue
reach the brainstem via
the vagus nerve.
On each side
conducting taste fibers
in these three nerves
unite in the gustatory
portion of the nucleus
tractus solitarius in the
medulla oblongata .
axons of second-order
neurons ascend to
reach posteromedial
nucleus of the thalamus
the axons of the thirdorder neurons pass in the
thalamic radiation to the
face area of the
somatosensory cortex in
the ipsilateralpostcentral
gyrus.
They also pass to the
anterior part of the insula.
The relevant insular
cortex is anterior to the
face area of the
postcentral gyrus and is
probably the area that
mediates conscious
perception of taste and
taste discrimination.
CN VII (facial), IX (glossopharyngeal),
and X (vagus) to Tractus Solitarius
• The dimensions of taste
Sour
Salty
Bitter
Sweet
Anthony J Greene
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• The salty taste is triggered by NaCl
• Salt-sensitive taste is mediated by a Na+selective channel known as ENaC.
• The entry of Na+ into the salt receptors
depolarizes the membrane, generating the
receptor potential
• The sour taste is triggered by protons (H+ions).
• ENaCs permit the entry of protons and may
contribute to the sensation of sour ataste
• Bitter taste is produced by a variety of
unrelated compounds. Many of these are
poisons.
• Some bitter compounds bind to and
block K+-selective channels.
• The sour taste is triggered by protons (H+ions).
• ENaCs permit the entry of protons and may
contribute to the sensation of sour ataste
• The H+ ions can also bind to and block a K+sensitive channel.
• The fall in K+ permeability can depolarize the
membrane.
• Substances that taste sweet also act via
the G protein gustducin.
• Umami taste is a pleasant taste
stimulated by mono-sodium glutamate ,
added recently to taste modalities .
References
• Human physiology by Lauralee Sherwood, 7th
edition
• Text book physiology by Guyton &Hall,12th
edition
• Text book of physiology by Linda .s
contanzo,third edition
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