Taste and Smell

Question 1

No. of taste buds?
Where are they?
4 types of lingual papillae?

Answer 1

4000
tongue, cheeks, soft palate, pharynx, epiglottis
lingual papillae = 4 types:
1) filliform - spiked, no taste buds - texture- most abundant
2) foliate - least abundant - gone by 2/3yrs
3) fungiform - 3 apical taste buds - especially at tip and sides of tongue
4) vallate - large(7-12), back of tongue- contain about 1/2 of all taste buds

Question 2

Where different tastes are tasted on tongue?

Answer 2

back of tongue
bitter
sour
salty 
sweet 
tip of tongue

Question 3

Names of different parts of tongue?

Answer 3

back of tongue
vagus
Glossopharyngeal IX
facial VII

(Looks at notes for images)
Also, look at where epiglottis, tonsilar fossa, lingual tonsil, circum vitae papillae, palantine tonsil and tonsilar fossa are

Question 4

A taste bud in the lingual papillae contains what?

Answer 4

epithelium, supporting cells, sensory cells, basal ganglia (10 day turnover) (40-60 cells)

Afferent fibres project from bottom

Question 5

What are each of the tastes from?
salty
sweet
sour
bitter
umami

Answer 5

salt - Na+ and K+ - vital electrolytes
sweet - sugars and carbohydrates - high energy food
sour - acids eg.citrus fruits
bitter - often poison
umami - amino acids, meat, monosodium glutamate

Question 6

High salt recruits aversive taste pathways!

Aversive or attractive taste?
Bitter and sour
sweet and umami
salt

Answer 6

bitter and sour = aversive
sweet and umami usually attractive
salt= unique, can transform an innately appetitive stimulus into an aversive one
receptor involves epithelial Na channel
balance regulates salt intake – high salt activate sour and bitter pathways
silencing pathways removes aversion response but not sensitivity to salt

Question 7

olfactory
sensitivity?
detect odours?
how do we smell?

Answer 7

v sensitive - few parts per trillion
detect 2000-4000 odours
sensory cells - neurons = only exposed nerve cells
molecule binds to receptor- opens Na+ channels, second messenger cAMP
adapt quickly -synaptic inhibition rather than in sensory cells

Question 8

sensory transduction?

Answer 8

odorant binding protein binds to odorant receptor = opens Na+ channels, Ca++ and Na+ pass through = 2nd messenger activated
(also, adenylate cyclase converts ATP to cAMP)
cAMP used in ion channel

Question 9

Structure of the nose

Answer 9

olfactory tract, olfactory bulb, olfactory fascicles, olfactory mucosa (look at images in notes!)

Question 10

What are fascicles?

Answer 10

slow unmyelinated fibres

Question 11

In the nose, we have:

Answer 11

Bowmans Gland (filled with mucus), cribiform plate and ethmoid bone

Fascicles send info above to olfactory bulb

Question 12

Inside olfactory bulb
3 cell types?
afferents?

Answer 12

tufted cells
mitral cells
granule cells
Trigeminal afferents(pain)

Question 13

Olefactory projections to:

Answer 13

olfactory cortex - conscious smell
Hippocampus - olfactory memory
Amygdala - emotional response
Hypothalamus - neuroendocrine and sex
reticular formation - visceral responses