Compare the neural mechanisms of smell and taste
Sanjay Manohar, Oxford 2017
Intro
extraordinary sensitivity
chemoception evolution old - food, defensive, social, navigation, mating
reward; drive appetite etc
pleasantness ~ 1/quantity
obesity; tax, education
Smell Anatomy
- naris, turbinates, palate, cribriform. obstructive apnoea
10m neurons. largest gene superfamily ~300 genes
clonal map: lineage correlates with glomerular choice. broad and narrow range.
thin dendrites, thru cribriform.
1000 glomeruli: synapse on Mitral, periglomerular, tufted cells.
granule cells - GABA
medial system - anterior commissure, olf tubercle, septal nn
lateral system - piriform cx (bypasses thalamus!),
also entorhinal, hippoc, amyg; newer: -> MDthal, insula OFC
POMC / NPY arcuate hypothal
Smell relevance:
anosmia - PD. glomeruli lost with age. head trauma
olfactory aura.
pheromones, vomeronasal organ?
cell turnover
mucus bowman's glands antibodies, odorant binding proteins
Gs-cAMP-Ca = action potential.
-> amplification
ligand gated salt / sugar; other GPCR too
-> adaptation, amplification
neural processing; labelled lines
-> lateral inhibition, deconvolve the broad receptor sensitivity
Taste
- facial, glossopharyngeal -NTS - gustatory thalamus - insula
- hydrophilic, nonvolatile.
- foliate, fungiform, filiform, circumvallate papillae
- receptors 2 wk turnover. microvilli, ATP/5HTergic.
- sweet/umami/bitter: TRPM5 receptors Gq/Na -> GLP1,NPY (autocrine)
- sour/salt: TRPP receptors/Ca -> 5HT, ACh, NA, gaba at synapses