Taste (gustation) Flashcards
Which of the following taste papillae does not contain taste buds?
A. Fungiform
B. Circumvallate
C. Foliate
D. Filiform
D. Filiform
How many taste buds are typically found in a single circumvallate papilla?
A. 3
B. 50
C. 250
D. 600
C. 250
Which neurotransmitters are primarily released by taste cells onto cranial nerves?
A. Dopamine and GABA
B. Serotonin and ATP
C. Acetylcholine and norepinephrine
D. Glutamate and glycine
B. Serotonin and ATP
Which taste is detected by GPCRs and involves the T1R1/T1R3 heterodimer?
A. Sweet
B. Bitter
C. Umami
D. Sour
C. Umami
Which cranial nerve is responsible for taste sensation from the anterior two-thirds of the tongue?
A. Vagus (X)
B. Glossopharyngeal (IX)
C. Facial (VII)
D. Trigeminal (V)
C. Facial (VII)
The inability to taste phenylthiocarbamide (PTC) is due to a mutation in which gene?
A. T1R1
B. T1R2
C. T2R
D. mGluR4
C. T2R
What is the typical detection threshold for bitter compounds like quinine?
A. 0.008 mM
B. 2 mM
C. 20 mM
D. 10 mM
A. 0.008 mM
Which type of cells in taste buds are responsible for regenerating taste cells?
A. Basal cells
B. Gustatory cells
C. Supporting cells
D. Stem cells
A. Basal cells
Which ion channel is critical for transducing sour taste signals?
A. TRPM5
B. ENaC
C. HCN
D. ASIC
B. ENaC
Where is the primary gustatory cortex located?
A. Temporal lobe
B. Parietal lobe
C. Insular cortex
D. Occipital lobe
C. Insular cortex
Describe the role of microvilli in taste cells.
Microvilli on taste cells increase the surface area for chemical interactions and contain taste receptor proteins that detect dissolved chemicals, concentrating them at the taste pore to enhance taste perception.
Explain how bitter taste signals are transduced in taste cells.
Bitter taste signals are detected by T2R receptors, which are G-protein coupled receptors (GPCRs). Upon activation by bitter compounds, they initiate a signal transduction cascade involving the specific G protein α-gustducin, leading to the release of neurotransmitters that communicate the bitter taste to the brain.
What is the significance of the TRPM5 channel in taste perception?
The TRPM5 channel is crucial for the transduction of sweet, bitter, and umami tastes. It is involved in the downstream signaling pathways of these tastes, and its proper functioning is necessary for the perception of these taste modalities.
Discuss the process of taste transduction from the detection of a taste stimulus on the tongue to the perception of taste in the brain. Include in your discussion the types of taste receptor cells, signal transduction pathways, and neural pathways involved.
Taste transduction begins when dissolved chemicals in food interact with taste receptor cells located in the taste buds on the tongue. These taste buds are housed within various types of papillae, such as fungiform, circumvallate, and foliate, each containing a different number of taste buds.
There are five basic tastes: bitter, sour, sweet, salty, and umami. Bitter, sweet, and umami tastes are detected by G-protein coupled receptors (GPCRs). Bitter taste involves T2R receptors, sweet taste involves T1R2/T1R3 heterodimers, and umami taste involves T1R1/T1R3 heterodimers as well as mGluR4 receptors. Upon binding of the respective ligands, these receptors activate a cascade involving the G protein α-gustducin and other downstream molecules like PLCβ2 and TRPM5 channels.
Sour and salty tastes are detected via ion channels. Sour taste is primarily transduced by proton-sensitive channels, while salty taste is mediated by epithelial sodium channels (ENaCs).
Once the taste receptor cells are activated, they release neurotransmitters such as serotonin and ATP onto the afferent nerve fibers of cranial nerves VII (facial), IX (glossopharyngeal), and X (vagus). These cranial nerves carry the taste signals to the gustatory nucleus in the medulla oblongata.
From the gustatory nucleus, second-order neurons project to the ventral posterior medial (VPM) nucleus of the thalamus. The VPM nucleus then relays the taste information to the primary gustatory cortex located in the insular cortex and frontal operculum. This region processes the taste information, leading to the conscious perception of taste. Additionally, the orbitofrontal cortex integrates taste information with other sensory inputs, contributing to the perception of flavor and the regulation of satiety.
The entire process ensures that taste stimuli are detected, transduced, and processed efficiently, allowing for a nuanced perception of different tastes and contributing to the overall sensory experience of eating.
