NS 12: Olfaction and Taste
Physician Assistant Pa 2013 Session 1 with Tsai at Touro University (NV)
About this deck
By: John Yaw-Jong Tsai
Created: 2011-10-09
Size: 32 flashcards
Views: 3
Created: 2011-10-09
Size: 32 flashcards
Views: 3
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What are the associated nuclei of olfactory system?
Associated nuclei
Striatum Cerebellum Raphe Locus ceruleus Hippocampus Hypothalamus
Striatum Cerebellum Raphe Locus ceruleus Hippocampus Hypothalamus
What are the sensory components of olfactory system?
olfactory epithelium
olfactory bulb
olfactory cortex
olfactory bulb
olfactory cortex
What type of epithelium lines the top of nasal passages?
pseudostratified neuroepithelium
intermixed with respiratory epithelium covered by layer of mucus
intermixed with respiratory epithelium covered by layer of mucus
What cell types does the olfactory epithelium have?
olfactory receptor neurons (ORN)
basal cells (ORN) progenitor cells
microvillar cells
sustentacular cells
Bowman's glands
basal cells (ORN) progenitor cells
microvillar cells
sustentacular cells
Bowman's glands
How often are ORN replaced?
ORN are continually replaced from basal cells
renewed every 1 to 2 months (rare for renewal of brain neurons in adults
replacement does not keep up with degeneration over time
sense of smell decreases with age
renewed every 1 to 2 months (rare for renewal of brain neurons in adults
replacement does not keep up with degeneration over time
sense of smell decreases with age
Olfactory receptors are largest subfamily of G-proteins coupled receptors. T/F?
true
each ORN expresses only one odorant receptor
a single odorant can be recognized by multiple receptors
a single receptor can recognize multiple odorants
combination of possible receptor combination is much larger than number of known chemicals
each ORN expresses only one odorant receptor
a single odorant can be recognized by multiple receptors
a single receptor can recognize multiple odorants
combination of possible receptor combination is much larger than number of known chemicals
Volatile odorant molecules first contact the mucous layer secreted by the olfactory epithelium – dissolves into mucous. T/F?
true
hydrophobic odorants interact with odorant binding proteins within mucus to interact with receptors on cilia of olfactory neurons
hydrophobic odorants interact with odorant binding proteins within mucus to interact with receptors on cilia of olfactory neurons
What is the signal transduction mechanism of odor detection?
cAMP pathway
opens cation channels (K+, Na+, Ca2+)
IP3 pathway
GPCR → PLC → IP3
opens Ca2+ channels
opens cation channels (K+, Na+, Ca2+)
IP3 pathway
GPCR → PLC → IP3
opens Ca2+ channels
How does adaptation of olfactory system happen?
adaptation happens through Ca2+ modulation of activity of cation channel and adenylyl cyclase
desensitization of olfactory receptor by PKA
desensitization of olfactory receptor by PKA
All ORNs expressing a given receptor converge on only one or two glomeruli → important for odor discrimination. T/F?
true
complexes of synapses called olfactory glomeruli
complexes of synapses called olfactory glomeruli
What cells layers does olfactory bulb consist of?
mitral and tufted (M/T) cells
excitatory projection neurons
uses glutamate
periglomerular (PG) and granular cells
inhibitory interneurons
uses GABA
excitatory projection neurons
uses glutamate
periglomerular (PG) and granular cells
inhibitory interneurons
uses GABA
Odor processing in olfactory bulb is mediated how?
mediated by excitatory (glutamate) and inhibitory (GABA) microcircuits between projection neurons, interneurons and ORNs
important for odor discriminiation
important for odor discriminiation
How is odor processed in olfactory glomeruli?
intraglomerular circuits between ORN, M/T and PG neurons
amplify signal through glomerulus
interglomerular circuits via PG and T neurons
inhibit neighboring glomeruli in order to enhance contrast between neighboring glomeruli
amplify signal through glomerulus
interglomerular circuits via PG and T neurons
inhibit neighboring glomeruli in order to enhance contrast between neighboring glomeruli
How are granular cells involved in odor processing?
granular cells enhance contrast between distant glomeruli
act as filter - to allow only signal generated by high affinity odorant
act as filter - to allow only signal generated by high affinity odorant
What are the central afferents of olfactory bulb?
locus coeruleus (noradrenaline)
raphe nuclei (serotonin)
diagonal band of Broca (ACh)
olfactory cortical regions (glutamate)
these systems also modulate odor processing in olfactory bulb
raphe nuclei (serotonin)
diagonal band of Broca (ACh)
olfactory cortical regions (glutamate)
these systems also modulate odor processing in olfactory bulb
There is no thalamus relay in olfaction. T/F?
true
olfactory bulb is connected to brain through olfactory tract
terminates in primary olfactory cortex
olfactory bulb is connected to brain through olfactory tract
terminates in primary olfactory cortex
What is in the primary olfactory cortex?
anterior olfactory nucleus
olfactory tubercle
piriform cortex
anterior cortical amygdaloid nucleus
periamygdaloid cortex
lateral entorhinal cortex
olfactory tubercle
piriform cortex
anterior cortical amygdaloid nucleus
periamygdaloid cortex
lateral entorhinal cortex
Experience of flavor involves both olfactory and taste input. T/F?
true
direct and indirect projections to insular cortices
these areas also receive taste input
direct and indirect projections to insular cortices
these areas also receive taste input
What are the taste experiences?
sweet
salty
sour
bitter
umami
in taste buds
salty
sour
bitter
umami
in taste buds
Each taste bud is innervated by more than one nerve afferent fiber and an individual fiber innervate multiple taste buds. T/F?
true
taste buds receptor cells undergo continuous turnover every 10 to 14 days
taste buds receptor cells undergo continuous turnover every 10 to 14 days
What are the different papillae that taste buds are located in?
fungiform 25%
foliate 25%
circumvillate 50%
filiform papillae do not sense taste
foliate 25%
circumvillate 50%
filiform papillae do not sense taste
sweet at tip
sour at edges
bitter in back
salty in anterior edges
sour at edges
bitter in back
salty in anterior edges
Threshold for bitter substances is substantially lower than for other substances. T/F?
true
thresholds for
citric acid = 2mM
NaCl = 10mM
sucrose = 20mM
strychnine = 0.0001mM
thresholds for
citric acid = 2mM
NaCl = 10mM
sucrose = 20mM
strychnine = 0.0001mM
How can acidic food reduce salt sensation?
H+ of acid can diffuse through Na+ channel
(more slowly than Na+)
salty (and bitter and sour) foods directly interact with ion channels
therefore acidic foods can reduce salt due to competition
(more slowly than Na+)
salty (and bitter and sour) foods directly interact with ion channels
therefore acidic foods can reduce salt due to competition
What are the peripheral taste pathways?
CN VII - chorda tympani and greater petrosal nerve
anterior 2/3rd tongue
soft palate
CN IX - lingual-tonsillar branches
posterior 1/3rd tongue
CN X - internal laryngeal nerve
epiglottis and esophagus - more reflex than taste
anterior 2/3rd tongue
soft palate
CN IX - lingual-tonsillar branches
posterior 1/3rd tongue
CN X - internal laryngeal nerve
epiglottis and esophagus - more reflex than taste
Where are the soma of CN VII, CN IX and CN X (involved in taste) located?
geniculate ganglion (CN VII)
petrosal ganglion (CN IX)
nodose ganglion (CN X)
petrosal ganglion (CN IX)
nodose ganglion (CN X)
How does CN V also contribute to chemoreception?
CN V receptors are nociceptive
activated by irritants - e.g. sulfur dioxide in air pollution, ammonia in smelling salts, acetic acid in vinegar
CN V threshold is 100 times higher than threshold for normal odors or tastes
activated by irritants - e.g. sulfur dioxide in air pollution, ammonia in smelling salts, acetic acid in vinegar
CN V threshold is 100 times higher than threshold for normal odors or tastes
What is the transduction method of irritants such as capsaicin or menthol?
activation of cationic channels - transient receptor potential channels (TRP channels)
What are disturbances of olfaction?
dysosmia = disturbances of olfaction
hyposmia = reduced ability to smell
parosmia = incorrect identification of smell
phantosmia = smell of odor when there is no odor present
cacosmia = repugnant smells
hyposmia = reduced ability to smell
parosmia = incorrect identification of smell
phantosmia = smell of odor when there is no odor present
cacosmia = repugnant smells
What is specific anosmia?
lower sensitivity to odorant due to lack of functional receptor for particular odorant
e.g. 1 in 1000 people is insensitive to skunk (mercaptan)
e.g. 1 in 10 cannot detect hydrogen cyanide or ethyl mercaptan (added to natural gas)
e.g. 1 in 1000 people is insensitive to skunk (mercaptan)
e.g. 1 in 10 cannot detect hydrogen cyanide or ethyl mercaptan (added to natural gas)
What is complete loss of taste?
ageusia
local damage to taste buds
rarely encountered since it would require bilateral lesions of CN VII and IX
local damage to taste buds
rarely encountered since it would require bilateral lesions of CN VII and IX
What drug induced disturbances in small and taste are more common?
dysgeusias and parosmias are most common
About this deck
By: John Yaw-Jong Tsai
Created: 2011-10-09
Size: 32 flashcards
Views: 3
Created: 2011-10-09
Size: 32 flashcards
Views: 3
About StudyBlue
STUDYBLUE makes things that make you better at school.
Things like online flashcards with photos and audio.
Things like personalized quizzes and friendly reminders about when (and what) to study next.
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STUDYBLUE exists to make studying efficient and effective for every student, for free. Join us.
“Simply amazing. The flash cards are smooth, there are many different types of studying tools, and there is a great search engine. I praise you on the awesomeness.”
Dennis
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