09 16 2014 Chemosensation

Question 1

Olfaction

Answer 1

detection of volatile compounds (odorants) by the olfactory epithelium of the nose.
-can detect man-made chemicals

Question 2

anosmia

Answer 2

lost or impaired smell

Question 3

risk factors for losing smell?

Answer 3

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

Question 4

Olfactory epithelium (composition of cells in this area)

Answer 4

• 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

Question 5

Glomerulus of Olfactory epithelium

Answer 5

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

Question 6

Primary causes of olfactory dysfunction?

Answer 6

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

Question 7

Secondary causes of olfactory dysfunction

Answer 7

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

Question 8

Conductive loss of smell?

Answer 8

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

Question 9

Sensorineural loss of smell?

Answer 9

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
-Alzheimer's
MS
-Cognitive disorders

Question 10

Unilateral anosmia is caused by what?

Answer 10

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

Question 11

kallmann syndrome (KS)

Answer 11

(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

Question 12

Taste: (general/definition)

Answer 12

direct contact of water-soluble compounds with tongue papillae

• olfaction is much more sensitive than taste

Question 13

Five primary tate qualities/modalities?

Answer 13

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

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

Question 14

Anatomy of taste (type of taste buds)

Answer 14

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

Foliate papilla – side of tongue

Fungiform papillate - anterior 2/3 of tonuge

Question 15

Where are taste buds?

Answer 15

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

Question 16

Central pathway mediating taste?

Answer 16

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

Question 17

Gustatory cortex? (where?)

Answer 17

-Frontal operulum and insula

Question 18

What are the two models for neural encoding of taste?

Answer 18

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.

Question 19

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

Answer 19

taste and smell

Question 20

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

Answer 20

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.

Question 21

trigeminal chomoreception system?

-important for?

Answer 21

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)

Question 22

pheromones

Answer 22

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