15. Gustatory - Taste Flashcards
(29 cards)
Describe the central gustatory pathway.
gustatory afferents in the cranial nerves (facial + glossopharyngeal) –> gustatory nucleus, the rostral nucleus of Solitary Tract –> rNTS will relay info to the ipsilateral thalamus (AKA no decussation), the VPM nucleus –> primary gustatory cortex –> relay information to secondary gustatory cortex. The collaterals of the pathway also include amygdala and hypothalamus
Is there gustatory topography?
No, taste buds all over our palate are able to respond to many different tastes.
Type II
• Rounded cell body • α-gustducin positive • express only 1 of 3 types of GPCRs for Sweet, bitter, or Umami • Also express non-GPCRs for Salty + Sour • Non-synaptic paracrine communication
Salty Receptors:
• salt in the oral cavity leaks into the cells through ENAC channels • depolarization of the cell opens voltage gated Ca2+ channels, and causes release of serotonin type II
Which TBC types are capable of transduction?
Type II and Type III
What are Tastants?
– Non-volatile, soluble/hydrophilic molecules in saliva – activate taste receptors
– In general, tastant receptors have high threshold (mM), except bitter. We have a low threshold for bitter
Name the cranial nerves containing gustatory afferent fibers. Identify from where in the oral cavity the gustatory afferents carry information.
Facial nerve + Glossopharyngeal nerve Facial nerve, Gives rise to TWO branches: –> Chorda Tympani (CT) = info from fungiform + lateral foliate papillae – anterior part of tongue –> Greater Superficial Petrosal (GSP) – roof the mouth Glossopharyngeal nerve –> Info from posterior part of the tongue These two nerves synapse in the gustatory nucleus, are parts of the gustatory pathway.
Bitter receptors:
• Family of T2 receptor proteins • 30+ isoforms • Single protein • Low threshold (nM)
Fungiform Papillae
– their connective tissue cores look like little mushrooms. – Their taste buds are located towards the top of the structure
5) Know the steps in transduction for the 5 taste modalities. How do the structure of bitter receptors, sweet, and umami differ?
Bitter, Sweet, and Umami—-These utilize GPCRs Bitter receptors: • Family of T2 receptor proteins • 30+ isoforms • Single protein • Low threshold (nM) Sweet receptor: • T1R2 + T1R3 • Protein complex • High threshold (mM) Umami receptor: • T1R1+T1R3 • Protein complex • High threshold (mM) Salty • salt in the oral cavity leaks into the cells through ENAC channels • depolarization of the cell opens voltage gated Ca2+ channels, and causes release of serotonin type II Sour Both the influx of H+ and the fact that it can cause closure of K+ leak channels which leads to depolarization of the cell since the positive is no longer leaving the cell Then get opening of voltage gated Ca2+ channels to get neurotransmitter release
Identify factors contributing to across fiber patterning or population coding in the gustatory system.
– over 90% of TRCS express multiple receptor types, so — are sensitive to many taste modalities – every afferent fiber receives input from multiple TRCs within a single taste bud, and across multiple taste buds. – Usually one taste will dominate
What are the 5 taste modalities?
- Salty (salts)
- Sour (H+)
- Sweet (sugars)
- Umami (glutamate)
- Bitter (many)
Which taste receptors utilize GPCRs?
Bitter, Sweet, and Umami
Circumvalliate Papillae
– largest of the papillae – They have a valley that surrounds the papillae
Type I
• Supporting cells • dont know if they are capable of transduction
6) What does paracrine signaling play in the transmission of taste signaling?
• Paracrine signaling is important for type 2 taste receptors cells • ATP is released by type 2 in an activity dependent manner but not at the synapse, but through its own channel for paracrine signaling • TRCs can communicate with both type 3 TRCs and afferent fibers via non-synaptic ATP release, and can communicate with afferents via synaptic 5-HT release.
Two ways that TRC’s can communicate with afferents–
TRC’s communicate with afferents (Type III –> Afferent fibers)
- via synaptic 5-HT release
- via non-synaptic ATP release = paracrine signaling
Umami receptor:
• T1R1 + T1R3 • Protein complex • High threshold (mM)
Paracrine and synaptic signaling from Taste Receptor Cells (TRC’s)
Paracrine signaling
- TRCs communicate with each other via non-synaptic ATP release (Type II –> Type III)
- TRCs communicate with afferents via non-synaptic ATP release (Type II –> Afferent fibers)
Synaptic signaling
- TRC’s communicate with afferents via synaptic 5-HT release (Type III –> Afferent fibers).
What are the 4 types of human papillae? Which ones contain taste buds?
only 3 actually contain taste buds
1) Filiform Papillae
2) Foliate Papillae
3) Circumvalliate Papillae
4) Fungiform Papillae
Type III
• Narrow cell body • α-gustducin negative • Salty and Sour • Gustatory presynaptic cells— form traditional synapses with afferent fibers.
Collaterals of the Central Taste Pathway
NTS also projects to and receives input from:
1) Amygdala
2) Hypothalmas – hunger, satiety, Control of pituitary gland and autonomic nervous system.
Sour Receptors
Both the influx of H+ and the fact that it can cause closure of K+ leak channels, leads to depolarization of the cell (since the positive is no longer leaving the cell) – opening of voltage gated Ca2+ channels to get neurotransmitter release
Foliate Papillae
Foliate Papillae – taste buds are in the lateral walls of the papillae – their connective tissue cores look like leaves!
