Peterson - olfaction & taste

Question 1

innervation for anterior 2/3 of tongue

Answer 1

general sensory - trigeminal nerve

taste - facial nerve

Question 2

innervation for posterior 1/3 of tongue

Answer 2

general sensory - glossopharyngeal nerve

taste - glossopharyngeal nerve

Question 3

epiglottis and soft palate

Answer 3

do not detect taste

• detect good vs. bad food and for swallowing
• epiglottis (vagus for taste and sensory)
• soft palate (facial for taste, trigeminal for sensory)

Question 4

filiform papillae

Answer 4

most abundant, move food, not for taste

Question 5

fungiform papillae

Answer 5

anterior 2/3 of tongue –> facial nerve

-most abundant

Question 6

foliate papillae

Answer 6

• posterior –> glossopharyngeal nerve
• anterior –> facial nerve
• sides of tongue

Question 7

circumvallate papillae

Answer 7

glossopharyngeal nerve

• over 1/2 of taste buds
• on posterior of tongue

Question 8

cells of the taste buds

Answer 8

1. taste cells - detect tastant with microvilli
2. supporting (glial) cells
3. basal cells - replace dying taste cells

taste pore where tastant travels to activate microvilli

Question 9

taste receptor communication - 2 ways

Answer 9

1. tastant interacts with microvilli –> receptor depolarization –> + Na+ and influx –> release ATP from cell to bind to free nerve ending
2. same mechanism except use Ca++ channels and influx to trigger ATP release

Question 10

salty taste communication

Answer 10

Na+ signaling

-Na+ influx –> depolarization –> ATP release

Question 11

sour taste communication

Answer 11

acid signaling

• weak acids –> diffuse, dissociate, increase acidity, and activate channels releasing ATP
• strong acids –> activate pH sensitive channel (higher pH induces depolarization)

Question 12

sweet, umami, and bitter communication

Answer 12

different GPCRs –> dissociate –> 2nd messenger system to release intracellular Ca++ –> ATP release

Question 13

gustatory pathway

Answer 13

neurons activated by taste –> ganglion –> synapse on nucleus solitary tract

• 1st route: reflexive activity - neurons synapse in dorsal motor nerve of vagus
• 2nd route: travel to cerebral cortex - thalamus –> VPN –> gustatory cortex –> orbital cortex and amygdala

Question 14

label line vs. cross fiber coding

Answer 14

label line = each axon responds to one tastant better than others
cross fiber = all axons together determine taste

Question 15

olfactory neurons

Answer 15

bipolar neurons - dendrites detect odorants with cilia

-group of olfactory neurons –> olfactory fila that pass through cribriform plate to olfactory bulb

Question 16

olfactory receptors

Answer 16

each GPCR has specific protein receptors for odorants

• odorant binds to GPCR –> dissociate G protein –> + adenylyl cyclase and cAMP –> Na+, Ca++ influx, K+ efflux –> Cl- efflux –> AP firing
• Cl- efflux DEPOLARIZES the cell

Question 17

role of mitral cells

Answer 17

interact with olfactory epith. receptors to convey info. to olfactory tract

• dendrites enter flat end, axons leave pointed end
• different odorants activate different glomeruli

Question 18

signal pathways of olfactory tract

Answer 18

1. trigger anterior olfactory nucleus (AON) - crossing over

2. synapse at olfactory tubercle - attaches to brain

Question 19

conductive olfactory deficit

Answer 19

prevent odorants from reaching neurons

• nasal polyp
• septal deviation
• inflammation

Question 20

sensorineural olfactory deficit

Answer 20

injury to CNS or neurons

• head injury
• parkinson’s, Alzheimers

Question 21

excess activity

Answer 21

tumor causing perceptions of taste or smell