Flashcards in Chemical Senses: Smell and Taste Deck (33):
Do we often associate individual molecules with objects?
Nope, it's often a complex mix of molecules
Review: How long are the olfactory nerves?
Really short... just running in the cribriform plate
What area of the brain is responsible for smell detection?
The pyriform cortex
What area of the brain is responsible for connecting smell with emotion?
What is the accessory olfactory system used for?
Individuals of the same species signaling to eachother (sex, fear, etc.)
3 types of cells in the olfactory epithelium?
Olfactory Sensory Neurons (OSNs) aka Receptor Cells, Supporting cells, Basal cells
What do the basal cells do?
Stem-cell like: give rise to olfactory neurons and support cells
What kind of receptor do odorants hit?
GPCRs - with G(olf)
2nd messenger used in olfactory receptors? Downstream effects?
cAMP, depolarization with Na+ and Ca++ influx
Do we have a lot of genes for olfactory receptors?
Yes, about 400 functional genes (though most animals have more). Largest gene superfamily in genome.
How many types of odorant receptors are on one neuron?
Is there a 1:1 relationship between odorant and receptor?
No. That wouldn't make sense, as there are more about 400 things in the world to smell. One receptor can bind many molecules, one molecule may bind many receptors.
How are odor quality and intensity encoded?
Combinations of multiple receptors/neurons.
3 types of cells in the olfactory bulb?
Mitral/tufted cells, periglomerular cells, granule cells
What do the mitral/tufted cells do?
Receive inputs from OSNs, send axons to higher cortical regions (they do the real business here)
What do the periglomerular cells do?
Modulate inputs to mitral/tufted cells from OSNs
What do the granule cells ddo?
Modulate outputs from mitral/tufted cells to cortical regions
What are the glomeruli in the olfactory bulb?
Clusters of dendrites of mitral/tufted cells all receiving input from OSNs with the same receptor.
How would you describe the area that signaling from one type of olfactory receptor activates in the piriform cortex?
A disperse field of neurons for "ensemble coding"
3 ways to mess up olfaction?
conduction, sensineural (ciliopathy, shear injury after head trauma), central olfactory neural impairment
What's one test to evaluate olfaction clinically?
UPSIT - UPenn Smell Identification Test
What happens to smell when you get old? Why?
It gets worse. Vascular or mass lesions, and neurodegenerative disorders.
The 5 tastes? Which ones use ion channels? What do the rest use?
Salty (Na+) and sour use ion channels. Bitter, sweet, and Umami use GPCRs.
What area of the thalamus does taste hit?
Where's the primary gustatory cortex?
The insula - deep in the Slyvian fissure (aka lateral sulcus). Recall destroying your brains' cortices to look at it.
Where do taste afferents first synapse?
In the nucleus of the solitary tract.
What specific channel is used for Na+ tasting?
ENaC (epithelial Na+ channel)
What specific channel is used for H+ tasting?
TRP (transient receptor potential) channel
What do protons do to the ion channels?
open them, allowing Na+ in
What is the second messenger system in bitter, sweet, Umami GPCRs?
gustducin -> IP3 -> Ca++ influx -> depolarization
What is "labeled-line coding"?
Brain has specialized areas wired to the cells with a specific type of taste receptor. (contrast with diffuse, combinatorial coding of olfaction)
Why do medications often cause reduced taste?
Dry mouth. And you need saliva to taste things.