The Gustatory System Flashcards
What is the definition of Flavor?
it is a complex sensory experience resulting from a combination of olfactory,taste, and somatosensory cues present in food and beverages.
Taste buds:
What is their structure?
They are ovoid epithelial specializations with a fluid-filled constriction at the apical end (which is on the surface of the tongue) called the TASTE PORE
They are located on papillae
They are found on the tongue, palate, layrunx, pahrunx, and upper eophagus
Papillae
What are the 3 types?
Fungiform, Circumvallate, and Foliate
Fungiform Papillae
Structure?
Location?
Number and location of taste buds?
1) mushroom shaped
2) Located on the anterior 2/3 of the tongue
3) contain 1-5 taste buds at their apical surface
Circumvallate Papillae
Structure?
Location?
Number and location of taste buds?
1) central bulges surrounded by circular trenches
2) Arranged in a chevron located at the rear of the dorsal aspect of the tongue
3) the contain about 250 taste buds along their trench walls
Foliate Papillae
Structure?
Location?
Number and location of taste buds?
1) Appear as a series of parallel clefts
2) On the lateral margin of the tongue
3) Contain about 600 taste buds in their cleft walls
Taste Receptor Cells
1) Structure
2) Function
1) Elongated epithelial cells that extend from the taste pore to the BASE of the taste bud.
Their apical ends are covered with microvilli that project into the taste pore. The microvilli contain receptors for tastant molecules
The basal ends of the cells fom chemical synapse like connections with the sensory neurons (gustatory afferent neurons).
These cells have a 10 to 14 day turnover.
2) gustatory transduction
Supporting cells
1) Structure
2) Function
1) elongated epithelial cells adjacent to taste receptor cells
2) Function unknown
Basal Cells
1) Structure
2) Function
1) stem cells located at the base of the taste bud
2) give rise to taste receptor cells
Gustatory Transduction:
What are the 5 basic stimulus qualities that the gustatory system distinguishes?
Salt, Sour, Sweet, Bitter, Umami
Gustatory Transduction:
What are the steps of gustatory transduction?
1) tastants diffuse through the fluid of the taste pore
2a) Salt and Sour stimuli (which are Na dependent) can flow into the taste receptor cell through selective (salt) and non-selective (sour) ion channels respectively
2b) Sweet, bitter, and umami stimuli bind to metabotropic receptors, ultimately causing release of calcium from intracellular stores
2c) Sour and bitter stimuli can close K+ ion channels (normally openat resting potential)
3) Depolarization caused by tastants towards the apical end of the taste cells opens Ca+ channels in the basal end of the taste cell allowing for release of neurotransmitter
Gustatory Transduction:
How do we discriminate tastants?
There is some evidence that different taste receptor cells respond to different stimuli but it is not know if each cell responds to one tastant or a combination of tastants
Processing gustatory information
What kinds of nerves innervate taste receptor cells?
Afferent only
Processing gustatory information
Where are the cell bodies of the taste sensory nerves located?
1) for taste receptor cells in the anterior 2/3 of the tongue and palate, cell bodies are located int he GENICULATE GANGLION of the FACIAL NERVE
2) for taste receptor cells in the posterior 1/3 of the tongue, cell bodies are located int he PETROSAL (aka inferior) NUCLEUS of the GLOSSOPHARYNGEAL GANGLION
3) for taste receptor cells of the epiglottis and upper esophagus, cell bodies are located in the NODOSE (aka inferior) GANGLION of the Vagus nerve
Processing gustatory information
What is the distribution of taste sensory neurons?
Each gustatory afferent neurons terminates on numerous taste buds, and within a single taste bud there are several taste receptor cells
