taste & smell basic neuroscience nbl 120 (2008). gustatory & olfactory systems extract...
TRANSCRIPT
Gustatory & olfactory systems
• Extract information from chemicals in the environment
• G-protein coupled receptors• Taste: (+ ion channels)
• Taste and olfactory receptor cells undergo continual lifetime turnover• Taste: modified epithelial cells• Smell: neurons
• Stimulus information is encoded in populations of neurons
Perception of flavor
• The chemical senses• Multiple components: • Taste buds• Olfactory receptors• Free-nerve endings (CN V)
e.g. spiciness & temperature
• Emotional and cognitive valence
Taste transduction
• Specific chemical interaction• microvillae• G-protein receptor• Ion channel
• Depolarization• Passive spread is enough• …but can produce APs
• Ca2+ entry• Transmitter (glutamate) release
G-proteins & ion channels
• Sweet• Salty• Sour• Bitter• “Umami”• TRP
channels (see PAIN)
Tim Jacob (Cardiff University, UK)
Anatomical path
• Rostral medulla• reflexes, e.g. DMN X
• VPM (head - sensory) • Cortical relay• via central tegmental tract (ipsi)
• Rostral pons• Parabrachial nucleus (non-human)
• Primary gustatory cortex• Insular / frontal operculum
Cortical processing
• orbitofrontal cortex• integration, e.g.,
olfactory information
• Projections• amygdala• hypothalamus• striatum
Anatomical points
• Olfactory receptor cells are real neurons• CN I & bulb is really part of the CNS• No thalamic relay
CNS pathways
• Anterior olfactory nucleus• Inhibit contralateral bulb
• Olfactory tubercule• Primary olfactory cortex• Piriform cortex• Periamydaloid cortex• (part of) parahippocampal gyrus
• Further projections• Limbic system - amygdala• Thalamus