Taste and Olfaction Study Guide

Question 1

What are the types of tastants?

Answer 1

salty, sour, bitter, sweet, umami

Question 2

Type I cell

Answer 2

-salt
-cell maintenance (Glial-like cell)
-no synapse
-release ATP
-Selective ion channel {Epithelium sodium channel (ENac)}
® Sodium enters via the ENac channel, depolarizing the cell
® They secrete ATP which activates taste axons

Question 3

Type II cell

Answer 3

-sweet, bitter, umami
-no synapse
-release ATP
-express G-coupled protein receptors
(diff. ones for diff. tastes)
® When a tastant binds to a taste receptor, the inside portion of the receptor triggers a cascade of molecular events.
® Cause increase in Calcium and then release ATP, activating taste axons

Question 4

Type III cell

Answer 4

-sour
-synapse
-release serotonin
-Selective ion channel (Hydrogen)
® Sour comes in as Hydrogen, the more Hydrogen ions there are the more sour it is
® Another way it gets into the cell, the undissociated acid can enter and then dissociate
-Depolarizes, increasing calcium

Question 5

Type IV cell

Answer 5

-no tasting
-no transduction
-develop into type I, II, III
-Basal cells

Question 6

Taste pathway!

Answer 6

Taste receptor cell
-> Cranial nerves (Corda tympani VII, Glossopharyngeal nerve IX, Vagus X)
-> Nucleus of the Solitary tract of the Medulla
-> Thalamus (relay)
-> Insular cortex (tastant perception)
-> Orbitofrontal cortex (Multimodel; flavor, temperature, smell, touch)

Question 7

What are the types of papillae?

Answer 7

Filiform
Foliate
Fungiform
Circumvallate

Question 8

Filiform Papillae characteristics

Answer 8

= small structures on the tongue that provide most of its bumpy appearance
□ Have no taste function
□ In other animals, they have a different shape and function to help the animal drink (e.g. lapping up water)

Question 9

Foliate Papillae characteristics

Answer 9

= folds of tissue that contains taste buds
□ Located in the rear of the tongue, on the edges
-Fold on the side

Question 10

Fungiform Papillae characteristics

Answer 10

= mushroom-shaped papillae located on the edge of the tongue
□ Concentrated on the tip of the tongue
□ Elevated in people who are super taster
□ Multiple taste buds in each

Question 11

Circumvallate Papillae characteristics

Answer 11

= large circular mound-like structures that are located at the back of the tongue
□ Taste buds are located in the surrounding trench-like structure

Question 12

What are the Cranial nerves associated with taste?

Answer 12

Facial VII
Glossopharyngeal IX
Vagus X

Question 13

What physiological/anatomical quality makes some people super-tasters?

Answer 13

They have an elevated number of fungiform papillae at the tip of their tongue

Question 14

What type of receptors do odorants activate?

Answer 14

G-coupled protein receptors

Question 15

How is transduction begun in the cell?

Answer 15

-Odorant molecules act in the mucus layer of the epithelium
-Olfactory molecules bind to the G-coupled protein receptors on the cilia of the Olfactory sensory neurons
-Transduction occurs (action potential)
-The axons of the Olfactory sensory neurons (CN 1) travel through the cribriform plate and synapse into the Glomeruli within the Olfactory bulb
-The axons of the mitral converge to form the Lateral Olfactory Tract which goes from the Olfactory bulb to the Limbic system

Question 16

What are the properties of odorant molecules?

Answer 16

-Volatile (vaporable, able to float in the air)
-small mass
-Hydrophobic (avoid water)

Question 17

What brain regions do Olfactory sensory neurons project to?

Answer 17

-Primary Olfactory Cortex (Pyriform Cortex)
-Amygdala
-Septal Nuclei
-Hippocampus
-Entorhinal Cortex

Question 18

Where do Olfactory sensory neurons synapse?

Answer 18

Into the Glomeruli within the Olfactory bulb

Question 19

How do Olfactory sensory neurons work? How are they activated, how they transmit signals, where does the signal go afterward?

Answer 19

1-When inhale, the volatile odorants enter the nasal cavity where they come into contact with olfactory sensory neurons
2-Once the odorant binds to olfactory receptor, triggers a secondary messenger cascade, increases calcium levels within the neuron, and eventually triggers neurotransmitter (glutamate) release to stimulate postsynaptic neuron
3-Signal travels up olfactory nerve and into the olfactory bulb (process & send to higher brain regions: AMYGDALA & HIPPOCAMPUS)
4-Olfactory cortex interprets the signals

Question 20

Orthonasal Olfaction=

Answer 20

odorants enter your nose and onto your olfactory epithelium (‘smelling strawberries’)
§ Into nose
§ Smell

Question 21

Retronasal Olfaction=

Answer 21

odorants travel from the back of our mouth into our upper nasal cavity and onto the olfactory epithelium (‘strawberry flavor’)
○ Into mouth and out through your nose
○ Taste

Question 22

What are the types of cells in the Olfactory epithelium?

Answer 22

Supporting cells
Basal Cells
Olfactory sensory neurons

Question 23

Supporting cells

Answer 23

Non-neural cells that provide metabolic and physical support for the epithelium

Question 24

Basal Cells

Answer 24

§ Function- stem cells become supporting cells and Olfactory sensory neurons
§ Provides some ability to recover the epithelium

Question 25

What are the cell types in the Olfactory bulb?

Answer 25

Juxtaglomerular neurons
Mitral and Tufted neurons
Granule neurons

Question 26

Juxtaglomerular neurons

Answer 26

○ excitatory and inhibitatory neurons that surround the glomerulus
○ Nearby cells
○ These neurons help shape the neural representation of the odorant
○ Get feedback from the brain and modify the signal

Question 27

Mitral and Tufted cells

Answer 27

○ synapse in the glomerulus and send their axons to higher brain regions (i.e. projection neurons)
-To the olfactory cortex (multiple regions)

Question 28

Granule neurons

Answer 28

○ Deepest layer of the olfactory bulb is an extensive network of inhibitory neurons that account for the second layer or inhibition within the bulb
○ Inhibit mitral and tufted cells
○ Get feedback from the brain and modify the signal

Question 29

What cranial nerve is associated with olfaction? What is it made up of ? (i.e. axons of which cells from where to where?)

Answer 29

-Cranial I Nerve
-Axons of the Olfactory sensory neuron

Question 30

Flavor=

Answer 30

combination of retronasal olfaction and true taste

Question 31

Turbinate bones=

Answer 31

are a set of curved bony structures located inside the nasal cavity.

Question 32

Function of Turbinate bones

Answer 32

Air filtration, warming, humidification, and airflow regulation

Question 33

Mitral cells=

Answer 33

The deepest layer of neurons in the olfactory bulb
Each mitral cell responds to only a few specific odorants

Question 34

What is the function of Mitral cells?

Answer 34

○ synapse in the glomerulus and send their axons to higher brain regions (i.e. projection neurons)
To the olfactory cortex (multiple regions)

Question 35

Cribriform plate=

Answer 35

a bony structure which separates the nose from brain

Question 36

What is the function of Cribriform plate?

Answer 36

The axons of OSNs travel through the tiny holes of the cribriform plate (a bony structure which separates the nose from brain) and converge to form the olfactory nerve (CN I) to enter the olfactory bulb in the brain.

Question 37

Glomeruli=

Answer 37

dendrites of mitral cells

Question 38

What is the function of Glormeruli?

Answer 38

they are small, ball-shaped clusters of synaptic connections located in the olfactory bulb, where the axons of olfactory sensory neurons (OSNs) synapse with the dendrites of mitral and tufted cells, which are higher-order neurons involved in odor processing.