Lecture 20 Flashcards
(25 cards)
What are taste buds made up of?
Modified epithelial cells
- Each taste bud is a compact cluster of 50-100 columnar epithelial cells
Where are taste receptors located?
Taste receptors are located in taste buds on papillae of tongue
Describe Type I cells
Type I have glial-like role (uptake of transmitters & K+), probably not directly involved in taste sensation
Describe Type II cells
Type II have chemoreceptors (GPCRs) for sugars, amino acids, or bitter stimuli (usually only 1 stimulus type per cell)
Describe Type III cells
Type III (neuron-like) have ion channels to sense sour and (probably) salty stimuli
Which taste occur in Type II cells?
Sweet, bitter and umami
Which cell surface receptors are associated with Type II cells?
- Gq associated
- T1R sweet and umami
- T2R bitter
- TRPM5 is temperature sensitive (15 to 35 °C)
What are the chemical mechanics that occur in Type II cells?
1) Depolarisiation activates ATP channel
2) ATP creates depolarization
3) Neurotransmitter is released into synapse with afferent neuron
Which taste occur in Type III cells?
Sour
What are the chemical mechanics that occur in Type III cells?
1) Sour stimulus brings in hydrogen ions (H⁺) through channels
2) Inside the cell becomes more acidic (lower pH)
3) This blocks potassium (K⁺) leak channels
4) Cell becomes more positively charged (depolarises)
5) This opens voltage-gated sodium (Na⁺) channels
6) Depolarisation travels to the synapse
7) Calcium (Ca²⁺) channels open
8) Neurotransmitters are released to signal the brain through the afferent neuron
Which nerves are taste information carried by?
- Facial nerve (anterior tongue)
- Glossopharyngeal nerve (posterior tongue)
- Vagus nerve (epilglottis)
Describe the Taste Pathways
- Afferent fibres synapse in medulla
- Information relayed to thalamus then to cortex (near tongue somatosensory area
What are ‘Hot’ spicy tastes sensed by?
Heat and pain sensitive nerve fibres in the mouth that are stimulated by chemicals such as capsaicin and piperine
What do the Cilia contain in the Olfactory cells?
Receptor proteins that bind odorant molecules
Where does each olfactory neuron project?
- To one glomerulus in olfactory bulb
- Each glomerulus receives input from olfactory receptor neurons of the same receptor type
What are the output cells?
Mitral cells
Where does the Olfactory bulb axon project?
To the primary olfactory cortex
What are perceptions of smell modified by?
- Context
- Experience
- Adaptation
