Taste and Olfaction Study Guide Flashcards
What are the types of tastants?
salty, sour, bitter, sweet, umami
Type I cell
-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
Type II cell
-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
Type III cell
-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
Type IV cell
-no tasting
-no transduction
-develop into type I, II, III
-Basal cells
Taste pathway!
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)
What are the types of papillae?
Filiform
Foliate
Fungiform
Circumvallate
Filiform Papillae characteristics
= 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)
Foliate Papillae characteristics
= folds of tissue that contains taste buds
□ Located in the rear of the tongue, on the edges
-Fold on the side
Fungiform Papillae characteristics
= 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
Circumvallate Papillae characteristics
= large circular mound-like structures that are located at the back of the tongue
□ Taste buds are located in the surrounding trench-like structure
What are the Cranial nerves associated with taste?
Facial VII
Glossopharyngeal IX
Vagus X
What physiological/anatomical quality makes some people super-tasters?
They have an elevated number of fungiform papillae at the tip of their tongue
What type of receptors do odorants activate?
G-coupled protein receptors
How is transduction begun in the cell?
-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
What are the properties of odorant molecules?
-Volatile (vaporable, able to float in the air)
-small mass
-Hydrophobic (avoid water)
What brain regions do Olfactory sensory neurons project to?
-Primary Olfactory Cortex (Pyriform Cortex)
-Amygdala
-Septal Nuclei
-Hippocampus
-Entorhinal Cortex
Where do Olfactory sensory neurons synapse?
Into the Glomeruli within the Olfactory bulb
How do Olfactory sensory neurons work? How are they activated, how they transmit signals, where does the signal go afterward?
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
Orthonasal Olfaction=
odorants enter your nose and onto your olfactory epithelium (‘smelling strawberries’)
§ Into nose
§ Smell
Retronasal Olfaction=
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
What are the types of cells in the Olfactory epithelium?
Supporting cells
Basal Cells
Olfactory sensory neurons
Supporting cells
Non-neural cells that provide metabolic and physical support for the epithelium
Basal Cells
§ Function- stem cells become supporting cells and Olfactory sensory neurons
§ Provides some ability to recover the epithelium
What are the cell types in the Olfactory bulb?
Juxtaglomerular neurons
Mitral and Tufted neurons
Granule neurons
Juxtaglomerular neurons
○ 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
Mitral and Tufted cells
○ synapse in the glomerulus and send their axons to higher brain regions (i.e. projection neurons)
-To the olfactory cortex (multiple regions)
Granule neurons
○ 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
What cranial nerve is associated with olfaction? What is it made up of ? (i.e. axons of which cells from where to where?)
-Cranial I Nerve
-Axons of the Olfactory sensory neuron
Flavor=
combination of retronasal olfaction and true taste
Turbinate bones=
are a set of curved bony structures located inside the nasal cavity.
Function of Turbinate bones
Air filtration, warming, humidification, and airflow regulation
Mitral cells=
The deepest layer of neurons in the olfactory bulb
Each mitral cell responds to only a few specific odorants
What is the function of Mitral cells?
○ synapse in the glomerulus and send their axons to higher brain regions (i.e. projection neurons)
To the olfactory cortex (multiple regions)
Cribriform plate=
a bony structure which separates the nose from brain
What is the function of Cribriform plate?
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.
Glomeruli=
dendrites of mitral cells
What is the function of Glormeruli?
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.
