09 16 2014 Chemosensation Flashcards Preview

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Flashcards in 09 16 2014 Chemosensation Deck (22)
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detection of volatile compounds (odorants) by the olfactory epithelium of the nose.
-can detect man-made chemicals



lost or impaired smell


risk factors for losing smell?

-higher risk for toxic eposes
-negative impact on life : can't enjoy food or pleasant fragrances.
-associated with other diseases/conditions


Olfactory epithelium (composition of cells in this area)

-Olfactory Receptor Neurons (ORN)
-7 transmembrane G-protein coupled receptor
-alpha subunit is specific to ORNs

-olfactory knob and olfactory cilia -- site of signal transduction due to odor

-basal stem cell population -- 30-60 days

-support cells

-Bowman's gland = mucus-- allows detection of odor.

-mitral and tufted cell project fibers along olfactory tract. Mitral --> glomerulus of olfactory


Glomerulus of Olfactory epithelium

a single input goes into glomerulus put many neurons from regions can come to that glomerulus if the input matches up.

Glomerulus sums activity of all ORNs that express that single olfactory receptor


Primary causes of olfactory dysfunction?

1. Nasal/sinus disease
2. Occlusion
3. Head trauma (cranio-facial)
4. Smoking
5. Toxic exposure
6. Genetic -- specific anosmias


Secondary causes of olfactory dysfunction

1. Endocrine: adrenal cortical insufficiency, Kallmann syndrome
2. Neurological: Alzheimer's, Parkinson's, Hunginton' chorea
3. Cancer therapies - chemotherapy and radiation


Conductive loss of smell?

losses secondary to obstruction of the nasal airflow to the olfactory cleft.
-chronic rhinosinusitis, polyps


Sensorineural loss of smell?

losses secondary to damage to or dysfunction of the olfactory nerves anywhere from th olfactory receptors through the olfactory bulb to processing in brain centers.
-head trauma
-Cognitive disorders


Unilateral anosmia is caused by what?

Damage to olfactory epithelium, olfactory nerve, olfactory bulb OR olfactory tract causes what type of anosmia?


kallmann syndrome (KS)

(heterogeneous) congenital and irreversible form of hypogonadotropic hypogonadism (HH) associated with anosmia
-symptoms present at puberty

-both olfactory receptor neurons and GnRH come from olfactory placode


Taste: (general/definition)

direct contact of water-soluble compounds with tongue papillae

* olfaction is much more sensitive than taste


Five primary tate qualities/modalities?

salty (ion channel -- Na+ or K+)
sour (protons- through Na+ or K+ channels)

sweet (G--protein)
bitter (G-protein)
umami (G-protein)


Anatomy of taste (type of taste buds)

Circumvallate papillae (back of tongue - posterior 1/3)

Foliate papilla -- side of tongue

Fungiform papillate - anterior 2/3 of tonuge


Where are taste buds?

open onto the epithelial surface via a taste pore

embedded in papillae of lingual epithelium and in the oral cavity

non-neuronal but they are excitable

-different modalities have different thresholds


Central pathway mediating taste?

1. Anterior 2/3
-CN 7 -- chorda tympani branch
Geniculate ganglion

2. Posterior 1/3
- CN9 --lingual branch
Petrosal (inferior glossopharyngeal ganglion)

3. Epiglottis, posterior pharynx
- CN 10 - sup. laryngeal branch
inferior (nodose) vagal ganglion

All go through gustatory nucleus -- nucleus of solitary tract --> ventral posterior medial nucleus of thalamus to cortex


Gustatory cortex? (where?)

-Frontal operulum and insula


What are the two models for neural encoding of taste?

1. Labeled Line code : taste information is transmitted via specific receptors or cells which are tuned to particular qualitities of stimuli

2. Ensemble coding: pattern of responses to a particular stimulus which varies across receptors/cells.


What receptors (modalities) adapt to ongoing presence of a stimulus?

taste and smell


why is it hard for a patient to have a true gustatory disorder?

because 80% of a meal's flavor is a result of olfactory input.

Patients frequently interpret a loss of smell as a loss of taste.


trigeminal chomoreception system?

-important for?

functions in noxious stimuli detection (nocicieption)

-polymodal nociceptive fivers
-activated by chemical irritants that come into contact with the face or oral cavity.

-trigeminal nerve innervates the lingual nerve (comes off of mandibular nerve)



substances which are secreted to the outside by a second individual of the same species.

1. gender ID
2. reproductive status of potential mates
3. social dominance satis and aggression
4. bonding of mother with young

-urine or glandular secretions