Chemical Senses: Smell and Taste Flashcards Preview

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Flashcards in Chemical Senses: Smell and Taste Deck (33)
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1
Q

Do we often associate individual molecules with objects?

A

Nope, it’s often a complex mix of molecules

2
Q

Review: How long are the olfactory nerves?

A

Really short… just running in the cribriform plate

3
Q

What area of the brain is responsible for smell detection?

A

The pyriform cortex

4
Q

What area of the brain is responsible for connecting smell with emotion?

A

The amygdala

5
Q

What is the accessory olfactory system used for?

A

Individuals of the same species signaling to eachother (sex, fear, etc.)

6
Q

3 types of cells in the olfactory epithelium?

A

Olfactory Sensory Neurons (OSNs) aka Receptor Cells, Supporting cells, Basal cells

7
Q

What do the basal cells do?

A

Stem-cell like: give rise to olfactory neurons and support cells

8
Q

What kind of receptor do odorants hit?

A

GPCRs - with G(olf)

9
Q

2nd messenger used in olfactory receptors? Downstream effects?

A

cAMP, depolarization with Na+ and Ca++ influx

10
Q

Do we have a lot of genes for olfactory receptors?

A

Yes, about 400 functional genes (though most animals have more). Largest gene superfamily in genome.

11
Q

How many types of odorant receptors are on one neuron?

A

One.

12
Q

Is there a 1:1 relationship between odorant and receptor?

A

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.

13
Q

How are odor quality and intensity encoded?

A

Combinations of multiple receptors/neurons.

14
Q

3 types of cells in the olfactory bulb?

A

Mitral/tufted cells, periglomerular cells, granule cells

15
Q

What do the mitral/tufted cells do?

A

Receive inputs from OSNs, send axons to higher cortical regions (they do the real business here)

16
Q

What do the periglomerular cells do?

A

Modulate inputs to mitral/tufted cells from OSNs

17
Q

What do the granule cells ddo?

A

Modulate outputs from mitral/tufted cells to cortical regions

18
Q

What are the glomeruli in the olfactory bulb?

A

Clusters of dendrites of mitral/tufted cells all receiving input from OSNs with the same receptor.

19
Q

How would you describe the area that signaling from one type of olfactory receptor activates in the piriform cortex?

A

A disperse field of neurons for “ensemble coding”

20
Q

3 ways to mess up olfaction?

A

conduction, sensineural (ciliopathy, shear injury after head trauma), central olfactory neural impairment

21
Q

What’s one test to evaluate olfaction clinically?

A

UPSIT - UPenn Smell Identification Test

22
Q

What happens to smell when you get old? Why?

A

It gets worse. Vascular or mass lesions, and neurodegenerative disorders.

23
Q

The 5 tastes? Which ones use ion channels? What do the rest use?

A

Salty (Na+) and sour use ion channels. Bitter, sweet, and Umami use GPCRs.

24
Q

What area of the thalamus does taste hit?

A

VPM nucleus

25
Q

Where’s the primary gustatory cortex?

A

The insula - deep in the Slyvian fissure (aka lateral sulcus). Recall destroying your brains’ cortices to look at it.

26
Q

Where do taste afferents first synapse?

A

In the nucleus of the solitary tract.

27
Q

What specific channel is used for Na+ tasting?

A

ENaC (epithelial Na+ channel)

28
Q

What specific channel is used for H+ tasting?

A

TRP (transient receptor potential) channel

29
Q

What do protons do to the ion channels?

A

open them, allowing Na+ in

30
Q

What is the second messenger system in bitter, sweet, Umami GPCRs?

A

gustducin -> IP3 -> Ca++ influx -> depolarization

31
Q

What is “labeled-line coding”?

A

Brain has specialized areas wired to the cells with a specific type of taste receptor. (contrast with diffuse, combinatorial coding of olfaction)

32
Q

Why do medications often cause reduced taste?

A

Dry mouth. And you need saliva to taste things.

33
Q

When a patient comes in saying they can’t taste, what should you do?

A

See if they really mean that they can’t smell.

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