Physiology of Taste and Olfaction

Question 1

What tastes will cause ATP release?

Answer 1

Sweet
Umami
Bitter

Question 2

What tastes will cause serotonin release?

Answer 2

Salty

Sour

Question 3

ATP can have which effects on neuronal taste receptors?

Answer 3

It can stimulate serotonin release (salty, sour).

Activate autocrine signaling.

Question 4

Salty

Answer 4

Na+ enters via ENaC.
Ca++ enters
Depolarization
Serotonin release

Question 5

Sour

Answer 5

H+ inhibits K+ channels.
Increase Ca++
Depolarization.
Serotonin release.

Question 6

Sweet

Answer 6

Gq increases IC Ca++.
TRPM5 activation.
Depolarization.
ATP released thru Panx1.

Question 7

Umami

Answer 7

Same as sweet, but includes Gq protein mGluR4.

Question 8

Bitter

Answer 8

Same as sweet.

Question 9

Why is there high binding affinity for bitter tastants?

Answer 9

Because poisons are bitter tasting

Question 10

Gustatory cortex (3)

Answer 10

Postcentral gyrus
Frontal operculum
Insula

Question 11

Where do all the taste branches of CN VII, IX and X terminate?

Answer 11

Nucleus tractus solitarius

Question 12

Obitofrontal cortex

Answer 12

Integrates visual, SS, olfaction and gustatory stimuli.

Question 13

Amgydala’s role in eating

Answer 13

Emotional aspects of eating, memories, etc.

Question 14

Hippocampus’s role in eating

Answer 14

Homeostatic mechanisms of hunger (I’m hungry now, etc).

Question 15

How does an odorant lead to an IC cascade?

Answer 15

Odorant binds Golf which stimulates AC –> increase cAMP which opens CNGC (cyclic nucleotide gated channels) leading to cation influx and depolarization.

Question 16

How can you get used to a smell?

Answer 16

If the odorant persists, sensitivity of CNGC to cAMP decreases. This lowers cation influx or can be inactivated by receptor phosphorylation.

Question 17

Explain the relationship between an olfactory neuron and glomerulus and what they can detect

Answer 17

One neuron expresses receptor for only one odorant. They synapse into a glomerulus with neurons that detect similar odors.

Question 18

How can we detect so many smells?

Answer 18

One odorant can stimulate more than one receptor or combinations of different neurons, changes in conc, etc

Question 19

Granular cells and periglomerular cells do what?

Answer 19

Increase specificity of signal by inhibition (GABA)

Question 20

Olfactory system is the only sense that:

Answer 20

Does not go through the thalamus before going to the cortex.

Question 21

Pifiform cortex projection to the lateral hypothalamus controls:

Answer 21

Appetite

Question 22

Piriform cortex projection to thalamus to medial orbitofrontal cortex does:

Answer 22

Integration of taste, sight and smell.

Appreciates flavors of food.

Question 23

Anterior cortical amygdaloid nucleus

Answer 23

Emotional learning. Olfactory fear conditioning.

Question 24

Etorhinal cortex to the hippocampus is important for:

Answer 24

Memory formation

Question 25

How might a patient present with a loss of gustation and a loss of olfaction?

Answer 25

Everything is integrated in the medial orbitofrontal cortex

Question 26

Reversible hyposmia

Hyperosmia

Answer 26

Mucous may block odors from binding, like in a URI.

Can occur in migraines, psychotic states and pregnancy.