Exam2Lec1ChemSenses-Olfaction&Gustation Flashcards by Daniella Andre

Human can discriminate how many olfactory stimuli?

> 1 trillion olfactory stimuli

each with very specific pathways

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What type of neuron is OSN?

Bipolar

dendrites form clilia (located at the surface of epith w/ recept)

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In the olfactory epthelium, what can we find?

olfactory neurons, support cells, and basal cells

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400-500 genes in the human genome codes for how many olfactory receptors?

1,000

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Where does the olfactory neurons project its axon?

through crubiform bone into the olfactory bulb where they synpase with central nerv system neurons and they project to diff parts of the brain.

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Odorants tend to small volatile molecules that are
a. water soluble?
b. lipid soluble?

Lipid soluble

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What does benzaldehyde and benzoic acids smell like?

benzaldehyde: almond
benzoic acids: urine

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True or false: There are many sep genes responsible for diff odor receptors

true

there is a huge family of odor receptors in mammalian gene

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How many transmembrane domains does odor receptors have?

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Odor receptors are
A. nicotinic ACH
B. GPCR
C. muscuranic ACH
D. GlyR

GPCR

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ORs detect odorants based on what?

Size, charge, amino acid group, vibration

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Specific OR mRNAs are expressed where?:

Specific regions of the olfactory epithelium, suggesting a topographic distrubutions

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Why is the ORN sensitive?

It expresses a single subtype of OR

OR are expressed in diff areas b/c each OR neuron expresses only 1 type of OR , BUT each neuron can respond to many odor stimuli

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True or false: a single OR nerve (ORN) can respond only to one odorant.

FALSE is can repsond to single or multiple odorants

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What are the specialist receptors/organs?

Trance-amine associated receptors and vomeronasal organs

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Trace-amine associated receptors are found where? What does it use as as signal transduction? What is it highly selelctive for?

Found in all mammals, including humans
Uses Golf/cAMP signal transduction mechanisms (taar)
Highly selective and sensitive for specific pheromones

they are highly specialized w/in olfact epith and they are very rare, They are selctive in their activation

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Where can you find vomeronasal organs? What does it contain?

Found in non-ape mammals excluds humans
Contains specialist receptors specific to pheromones

these express vomeronasal receptors, not odor receptors

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1st rout of activation of OR is via release of olfactory G-protein (GOLF), explain this process

Odorant molecule binds to receptor protein. Golf is released, activating adenylate cyclase, producing cAMP, which binds and opens a cyclic nucleotide gated (CNGA) channel; (Na/Ca2+ influx (depolarization)
Ca2+ activates Cl- channel: Cl- efflux (further dep)
Depolarization triggers ap
Ca2+ lvsl restores by exchanges and pumps

like Gs

lots of dep bc lots of neg charge leaving and pos charge coming in

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What types of olfactory adaptation do we have?

Initial, short-term, long term

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What is initial adaptation?

Incr Ca2+ binds to Ca2+ binding protein (CBP) that desentitizes the CNGA channel

like a neg feedback

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What is short-term adaptation?

Incr desensitization via Ca2+ calmodulin protein kinase 2 acting on Adenylate cyclase (AC)

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What is Long term adaptation?

Ca2+ mediated NO production stimulated guanylate cyclase to produce cGMP (cG)

cGMP causes persisant Ca2+ influx thru CNGA channe; leading to further desensitization of CNGA and AC

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What is the 2nd route of activation of OR?

Via release of Olfactory G-protein (Golf)

acts like gq

activates PLP C -IP3 pathway which opens Ca2+ channels

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Axons of the ORN synapse where?

In the glomeruli of the olfactory bulb (OB).

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The glomeruli of the OB receives info from how many ORN and how many ORN axons?

Each glomerulis receives info from only ONE type of ORN but receives THOUSANDS of ORN axons which synapse with 20-50 relay neurons (mitral/tufted)

The OB can be diveded into how many layers?

What are the 5 layers of the olfactory bulb?

1. ORN/OSN 2. Odorant specific glomeruli (synapses) 3. external plexiform layer 4. mitral cell layer 5. granule layer

What is the mitral/ tufted layer of the olfactory bulb general fxn?

Receive info from OLN in glomerulus and relay up to olfactory tract in CNS.

What is the granule cell layer of the olfacgtory bulb generally involved in?

involved in incr or decr lateral inhibition effectivess

Where info from periphery enters CNS

Glomerulus

What increases odor discrimination (both at glomeruli and mitral/tufted)

Lateral inhibition

Via CN1 (olfactory nerve), mitral/tufted cells connected to a ____ show distinct patterns of projections to several areas of the olfactory cortex

single glomerulus

For olfactory projections, the mitral valve sends info to how many regions and what are they?

Sends info to 5 regions 1. ant olf. nucleus 2. olf. tubercle 3. piriform cortex 4. amygdala 5. entorhinal cortex

For olfactory projetions, what is the pathway responsible for odor perception and discrimination?

The pathway through the thalamus to the orbiotfrontal cortex

The pathways to the amygdala and hypothalamus is resppnsible for what aspects of smell?

Emotional and motivational aspects of smell Physiological and behavioral aspects of smell

What is responsible for odor induced fear signaling?

Amygdala-piriform boundary

Order of olfactory system

Olfactory epith olfactory bulb olfactory cortex ## Footnote this system is a network that contributes ti the summation of distinguishing smells

Olfactory impairment is a side effect of which diseases?

Parkinsons, Huntigtions, Alzheimers, Covid

Olfactory senescence begins at what age and involved the loss of smelling what type of odors?

Age 36 and involves the loss of smelling pleasant odors

Where are taste cell receptors located?

On the tongue, pharynx, palate, epiglottis, upper 3rd of the esophagus ## Footnote NOT NEURONS

Which CN innervate the gustatory system?:

VII, IX, X

CN VII (chorda tympani branch of facial) innervates via what?

Geniculate ganglion ## Footnote innervates tongue

CN IX (lingual branch of the glossopharyngeal) innervates via what?

Petrosal ganglion ## Footnote innv tongue

CNX (sup laryngeal branch of vagal) innervates via what?

Nodose ganglion ## Footnote does not inn tongue, it does pharynx, etc

Taste buds (containg taste cells) of the tongue are embedded where?

Papillae of the tongue

What innervates the anterior 2/3 of the tongue and what type of papillae can we find here?:

Inn by CNVII (chordi a tympani/facial) You can find fungiform & filiform papillae

What innervates the posterior portion of the tongue and what type of papillae can we find here?:

Inn by CN IX (glossopharyngeal) can find circumvallate and foliate papillae

What are the tastants and what molecules are responsible for them?

* Sweet-sucrose (threshold 20mM) * Salty-NaCl (threshold 10mM) * Sour-Citric acid (threshold 2mM) * Bitter- quinine (threshold 8microM) * Umami-glutamate (threshold 100microM) * Water

Specific taste occurs where?

across the whole tongue, just @ diff amounts

What are the diff types of taste cells that we have?

Type 1,2,3, basal cells ## Footnote type 1> type 2> type 3

Type 1 cells

Support fxn Putative (tentative) salt sensor ## Footnote type 1> type 2> type 3

Type 2 cells

* Contain the GPCRs signaling effectors for bitter, sweet and umami * Associate closely w/ afferent nerve fibers; DO NOT form conventional synapses ## Footnote type 1> type 2> type 2

Type 3 cells

* Respond to sour stimuli * form prominent synapses with afferent nerve fibers * Vesicular release of serotonin and ATP ## Footnote type 1> type 2> type 2

Basal cells

progenitor cells (10 day turnover rate)

Type 2 cells respond to what type of tastant stimuli?

Umami, sweet, and bitter

Umami has what type of receptor? Made up of what proteins? | type 2 cell

1 T heterodimer GPCR proteins: T1R1 + T1R3 ## Footnote need to have both activated in order to have activation of GPCR

Sweet has what type of receptor? Made up of what proteins?

1 T heterodimer GPCR Protein: T1R2 + T1R3 ## Footnote expressed in T1R2 and 3

Bitter has what type of receptor?

30 T2Rs ## Footnote Monomor GPCR mediated by T2 receptor family

Type 1 cells respond to which taste stimuli?

Sodium

What is the receptor for sodium?

ENaC ## Footnote ion channel

Type 3 cells responds to what taste stimuli?

Sour and carbonation cells ## Footnote ion channel

What is the receptor for sour?

PKD2L1

Sour is a sensation caused by ____ acidification of type ____ cells (membrane permeable acids are more potent tastants)

Intracellular, 3 ## Footnote not gpcr

Explain type 2 signal transduction

1. Sweet/umami/bitter enters ton gue and binds to GPCR taste receptor 2. G. gustucin (like a gq) 3. PLP C is activated, IP3 activates, and causes release of Ca2+ from ER. 4. TRPM5 channel is now activated and allows Na+ rushing in causing dep and ap 5. **CALMH1 channel is now activated and allows ATP to flow out activating the nerve. (its a NT pore)** ## Footnote CALHMI: calcium homeostasis modulator 1 (voltage -gated channel)

High sensitivity salty taste is at high or low concentration of salt?

Low

High salt sensitivity is responsible for salt ____. Via what?

salt attraction via epitheliali sodoum channel (ENaC)

Salt attraction is sensitive to? a. NaCL only b. KCL and CsCl only c. All of the above

NaCl only

Salt attraction is inhibited by what?

Amiloride

are type 1 cells responsible for salt aversion?

NO, type 2 cells are

Low sensitivity salty taste is at high or low concentration of salt?

high

Low salt sensitivity is responsible for salt ____. Via what:?

aversion, bia bitter receptors on type 2 cells

Salt aversion is sensitive to? a. NaCL only b. KCL and CsCl only c. All of the above

all of the above

What type of expressing cells are critical for sour sensing?

PKD2L1

Citric acid (sour) induces cation influx via what?

PKD heterodimer

Does PKD knock out eliminate sour sensing?

NO, only reduces

What are the two types of afferent nerves/fibers associated with taste cells:?

Intragemmal fiber (gustatory nerves) Perimeggmal fibers (somatosensory nerves)

What are the gustatory nerves that innervate taste bud/cell

CN VII, IX, X

Gustatory nerves contain what type of receptor that is critical for all tastes?:

G-gustucin-P2X2/3 ## Footnote atp sensitive ion channel gettting rid of ATP pathway (which activates these nerves, you gt rid of nerve acitvation

What is the somatosensory nerve that play a role in chemesthesis?

CN V (trigeminal)

Communication between TC and afferent nerve requires ____ and ____ ion channels

purinergic, serotnergic ## Footnote if you were to ko purinergic channel ATP channels, you wipe out sensitivity of nerve

For Intragemeal fibers (gustatory nerves), type 2 cells release ATP via what?

Via CalHM1 (non vesicle)

For Intragemeal fibers (gustatory nerves), type 3 cells release ATP and 5-HT via what?

via vesicles

What is the enzyme that breaks down ATP signals?

NTPDase

Possible inter TRC communication is due to cross talk with which molecules?

ATP, GABA, and 5HT

# inter-TRC communication Activated Type 2 cells release ATP which does what to Type 3 cells

activates Type 3 cells

Activated Type 3 cells release GABA and 5HT which does what to Type 2 cells

inhibits Type 2 cells

In the somatosensory system, we have many trigemminal nerves in the tongue and these are perigemmal fibers. Are these perigemmmal fibers interacting with taste cells?

NO, they free nerve endings that detect aversive stimuli (pain) and temp in the oral cavity (chemesthesis) ## Footnote senses pungencey not taste

What ate the nociceptors subtypes for the perigemmal fibers?

TRPV1: chili (capsaicin), heat, acid TRPA1: wasabi TRPM8: menthol, cold

Perigemmal fibers have CNS projections to the ____ in the medulla and onto the thalamus to modulate taste and in some cases, evoke ____.

Sp5, defensive reflexes

Projections of the various gustatory nerves travel to the cortex via

1. **Nucleus of the solitary tract (NST)** in the medulla 2. NST cells send fibers to cortex via ventral posterior **medial thalamus (VPM)** and the **parabrachial nuc (PbN)** 3. In the **gustatory nuc (GN)** of the cortex, info is sep from other sensory modalities of the tongue

What are the 3 types of info extracted from tastants?

Quality, intensity, hedonic value

What does quality of a tastant mean?

Is it salty, sweet, etc

What does intensity of a tastant mean?

How sweet is it, how salty is it, etc

What does hedonic value of a tastant mean?

Perceived pleasantness or unpleasantness of a stimulus can be measured by ingestive vs protective behaviors

In the CNS there is is an ____ of neuronal responses such as sweet, salt, and sour, but none between _____.

overlap, bitter and sweet ## Footnote no structural differance, they oppose each each other (salty and sour don't have opposites)

Stimuli such as sweet, salty, etc cause motor driven behaviors that result in ____ or ____ responses.

ingestive, protective ## Footnote ingestive: tongue protrusions, salivation, insulin release, swallign protective: gapes, chin rubbing, coughing, apnea, salivation

Exam2Lec1ChemSenses-Olfaction&Gustation Flashcards

(96 cards)