Olfaction and Taste

Question 1

What are the two critical problems the taste system must solve?

Answer 1

1. Will it kill me?

2. Will it keep me alive?

Question 2

What are the five fundamental tastes?

Answer 2

sweet, salty, umami, sour, and bitter

Question 3

What do each of the five fundamental tastes signal?

Answer 3

• sweet: calories in the form of carbohydrates
• salty: water homeostasis
• umami: calories in the form of protein
• sour: spoilage
• bitter: toxicity/poisonous

Question 4

What cranial nerves mediate taste?

Answer 4

• CN VII: anterior 2/3 of tongue
• CN IX: posterior 1/3 of tongue
• CN X: sensory from oral cavity

Question 5

Pathway of taste

Answer 5

• Inputs from CN VII, IX, X cometogethr in the brainstem in the solitary tract and synapse in the solitary nucleus. —From the solitary nucleus, these second order neurons synapses in the ipsilateral ventral posteromedial nucleus of the thalamus.
• Third order neurons project from the VPM to the gustatory cortex of the insula

Question 6

What are papillae?

Answer 6

the protrusions on the surface of the tongue

Question 7

What are taste buds? where are they found?

Answer 7

bundles of taste cells bundled together; found in the papillary troughs

Question 8

What are taste cells?

Answer 8

the electrically excitable sensory cells for taste (NOT neurons) that release neurotransmitters at their base and activate the gustatory afferent cells

Question 9

What are gustatory afferents?

Answer 9

the neurons that take information into the CNS

Question 10

What are taste pores?

Answer 10

interact with the external environment, found at the apical ends of taste cells

Question 11

CN VII

Answer 11

taste from anterior 2/3 of tongue

Question 12

CN IX

Answer 12

taste from posterior 1/3 of tongue, sensation from tonsils, pharynx, middle ear and cartoid sinus

Question 13

CN X

Answer 13

sensation from epiglottis, base of tongue, upper larynx

Question 14

What pathway is responsible for concious perception of taste?

Answer 14

VPM to gustatory cortex

Question 15

What are some pathways for unconcious taste information?

Answer 15

solitary nucleus to nucleus amgiuus for gagging
solitary nucleus to parabrachial pontine nucleus to amygdala (emotional stimuli) or hypothalamus (especially for salt taste) for regulating fluid and ion balance

Question 16

Where is the gustatory cortex located?

Answer 16

spread between the insula and frontal operculum

Question 17

What is the role of the insula?

Answer 17

helps translate sensory signals into subjective feelings, like hunger, pain or craving, that drive behavior

Question 18

The olfactory pathwyas are contained entirely within the ______

Answer 18

telencephalon

Question 19

Odorants are sampled by airflow through the _______

Answer 19

nasal turbinates

Question 20

Where do olfactory receptors reside?

Answer 20

they line the nasal turbinates

Question 21

Receptor neurons converge onto how many glomeruli in what structure?

Answer 21

a single glomeruli in the olfactory bulb

Question 22

Where do the cell bodies of sensory neurons reside?

Answer 22

within the olfactory epithelium

Question 23

Where do the axons of olfactory sensory neurons project to?

Answer 23

project rhough the cribiform plate an converge on the glomerulus

Question 24

All cels with the same type of receptor project to _______

Answer 24

the same glomerulus

Question 25

Does the olfactory pathway pass through the thalamus?

Answer 25

NO

Question 26

What is the role of the olfactory tubercule?

Answer 26

part of the striatum, associates odor with reward

Question 27

What is the role of the piriform cortex?

Answer 27

concious perception of odor

Question 28

Olfactory pathway

Answer 28

olfactory mucus to olfactory bulb to olfactory tubercle/piriform cortex/amygdala/lateral entorhinal cortex to lateral hypothalamus/dorsomedial thalamic nucleus/insular and orbital cortex to olfactory bulb

Question 29

What is the vomeronasal system?

Answer 29

a cehmosensory pathway responsible for driving behaviors relating to interacting with other animals (mating, avoidance, aggression)

Question 30

Vomeronasal pathway

Answer 30

non-volatile odors go to the vomeronasal organ. The vomeronasal organ has projections to the accessory olfactory bulb, which outputs to the medial amygdala and hypothalamus

Question 31

Does the vomeronasal system project directly to the cortex?

Answer 31

No

Question 32

What is flavor?

Answer 32

a combination of the preception of taste, smell, and texture

Question 33

Why might the orbitofrontal cortex be a site for flavor integration?

Answer 33

- it integrates multimodal information related to flavor | - recieves inputs from piriform and gustatory corticies

Question 34

What is the relevance of the olfactory and taste corticies projections to the amygdala/limbic system?

Answer 34

this impacts perception of taste and smell

Question 35

How do glomeruli constititute a map of receptor identity?

Answer 35

because each neuron only expresses one receptor type and each glomeruli only recieves input from one receptor type, you end up with a map. Also as different odors activate different glomeruli, there is a different map of acitivty in the brain in response to different odors

Question 36

Is the map that exists in the glomerulus present beyond the olfactory bulb?

Answer 36

no, because a single glomerulus projects to widespread areas of the olfactory cortex so it isn't possible to map it