4. Introduction
Taste - French word ‘taster’ means to touch
Definition: Taste is the detection and recognition of substances in solution.
A specialized chemical sensory function of brain.
Molecules of taste - Sapid
5. Importance of taste
1.Appreciation of food and drink.
2.Selection of food.
3.Protection against toxins.
4.Important for the dentist:
• stimulates salivary secretion
• governs use of oral hygiene aids.
6. Taste Buds & Gustatory
Papillae
• Taste buds – specialized organs of taste
• Location: Mucosa of tongue, soft palate,
pharynx, epiglottis and esophagus.
• Young adult – approximately 9000 taste buds.
16. 3. Basal cells
Small irregular epithelial cells - base of the
taste bud - connective tissue layer.
17. Electron microscopy – 4 types of cells
Type I cells / dark cells (60%)
– Columnar cells – short microvilli
– Nuclei – darkly stained ; Cytoplasm - dark membrane bound
granules
– Function – secretion of glycosaminoglycans
18. • Type II cells or light cells (30-40%)
– Columnar cells- thick and short microvilli
– Nuclei – lightly stained
– Vesicles present immediately below microvilli but no
synapse like feature
– Function - not known
19. • Type III cells / intermediate cells (5 – 15%)
– Columnar cells with short microvilli
– Basal end – cytoplasmic vesicles – synapse with nerve fibers
– Function – taste perception
• Type IV cells / basal cells
20. Sensory Innervation of the taste bud
Sensory nerve fibers – two groups
1. Intragemmal plexus
2. Perigemmal plexus
• Single taste bud – more than
one nerve fiber
– Single nerve fiber –
more than one taste
bud
23. Sensory mechanisms of taste
1. Enzyme theory
2. Membrane permeability theory
Enzyme theory:
Inhibition or potentiation of enzymes of
pore substance
↓
24. Baradi and Bourne (1951)
sapid substance
↓ (influence on)
enzyme activity
↓
enzyme reaction (altered)
↓
change in concentration of ions and
organic compounds
↓
26. Demerits of Enzyme Theory
1. No evidence of influence of enzyme products
on nerve endings.
2. Action potentials develop very rapidly.
27. Modern concept of membrane permeability
Sapid substance + receptor
↓
Change in membrane permeability of
receptor
↓
Depolarization
↓
Action potential/receptor potential in
cell
↓
Calcium influx
↓
28.
29.
30. Salivary - gustatory complex
Nucleus of tractus solitarius
Superior salivary Inferior salivary
nucleus nucleus
Submandibular Otic ganglion
31. Factors affecting taste
perception
1. Taste adaptation:
Stimulus on a receptor for a long time
↓
nerve impulses decreases
↓
reduced taste sensation.
32. 2. Temperature:
Cold food – ↓ ability of
receptors – poor stimulation
Hot food – ↑ ability of
receptors – good stimulation
3. Hormonal influence:
Increased sensitivity to bitter taste and smell
– menstruation
33. 5. Age:
↓ taste sensitivity
6. Genetic variation:
70% caucasian population – positive response
to bitter taste of Phenylthiocarbamide
30% no response
37. Conclusion
Taste helps to identify toxins and maintain
nutrition. Taste helps you detect spoiled
food or liquids and, for some people, the
presence of ingredients to which they are
38. References
• Applied oral physiology -christopher.L.B.Lavelle
• Text book of physiology-sembulingam.
• Oral and maxillofacial pathology – Neville
• Burket’s oral oral medicine, diagnosis and treatment.
• Text book of human physiology –A K jain
• Text book of medical physiology-guyton.
• Thieme - Textbook of head and neck anatomy for
dental medicine
Editor's Notes
When food or other substances enter the mouth, molecules interact with saliva and are bound to taste receptors in the oral cavity and other locations. Molecules which give a sensation of taste are considered "sapid"
Characteristic feature of this papilla is presence of serous minor salivary glands (von-ebners glands) in the connective tissue beneath it.
These glands secrete watery saliva in to V-shaped trough around the papillae to flush out debris.
1. Sustentacular Cells / Supporting Cells (Dark Cells):
These are columnar cells with darkly stained round or oval nuclei & a granular cytoplasm. These cells form an outer capsule.
2. Gustatory / Receptor Cells (Light cells):
These are columnar cells with oval nuclei & a lightly stained cytoplasm. A single hair like gustatory hair (microvillus) projects from each gustatory receptor cell to the external surface through the taste pore. At their base, taste cells synapse with the dendrites of 1st order neurons. Hence these cells are considered to be the gustatory receptor cells.
3. Basal Cells:
These are small, irregular cells found close to the base of the taste bud near the connective tissue layer.
These epithelial cells produce supporting cells, which then develop into gustatory receptor cells that have a life span of about 10days.
An intact nerve supply is necessary for the normal function of taste buds. Damage to the nerves innervating the taste buds showed degeneration of the taste buds & the taste buds subsequently disappear. Following regeneration of the appropriate nerves, the taste buds reappear & assume normal function.
In 2010, researchers found bitter taste receptors in lung tissue, which cause airways to relax when a bitter substance is encountered. They believe this mechanism is evolutionarily adaptive because it helps clear lung infections, but could also be exploited to treat asthma and chronic obstructive pulmonary disease.
diglyceride, or diacylglycerol (DAG), inositol trisphosphate (IP3). Transient receptor potential cation channel subfamily M member 5 is a key component of taste transduction in the gustatory system of bitter, sweet and umami tastes being activated by high levels of intracellular calcium.
