Topic 12: Chemical Senses

Question 1

taste

smell/olfaction

Answer 1

• molecules entering mouth and stimulating taste receptors on tongue
• molecules entering nose and stimulating odor receptors on olfactory mucosa

Question 2

flavour

gatekeepers

Answer 2

• result of taste and olfaction being integrated

- taste and smell help us determine what to consume and what not to consume

Question 3

five basic taste qualities

Answer 3

bitter - can signal poisons and toxicity
sour - can signal under-ripe fruit and spoiled foods/meat
-salty - can signal sodium ions necessary for basic cellular processes
sweet - can signal carbs which are major source of energy
-umami - signal proteins that supply amino acids important for health

Question 4

4 types of papillae on tongue

Answer 4

filiform - shaped like cones and cover whole surface
fungiform - shaped like mushrooms and found on sides/tip
-foliate - series of folds on back and side
-circumvilliate - shaped like flat mounds in a trench and located at back

Question 5

taste buds

Answer 5

-located in papillae except for filliform
most on tongue, others on roof, sides back and throat
each bud has cells with tips that extend into taste pore
-transduction occurs when chemicals contact receptor sites on tips

Question 6

taste receptors

Answer 6

molecules bind to receptors changing ion flow across cell membrane
similar action as neurotransmitter
salt ions can break down and enter the cell itself

Question 7

taste pathway

Answer 7

chorda tympani - nerve from front and sides of tongue
glossopharyngeal nerve - from back of tongue
vagus nerve - from mouth and throat
all 3 converge in nucleus of solitary tract in medulla
thalamus –> cortex = insula and frontal operculum

Question 8

role of smell

Answer 8

-compliment to taste (flavour)
warning system
communication system for pheromones
cue for memory -LTM

Question 9

microsmatic

macrosmatic

Answer 9

• less keen sense of smell thats not crucial to survival - humans (10 mil olfactory receptors)
• keen sense of smell thats necessary for survival (rats, bee’s etc), 300x sense of smell of humans

Question 10

Bushdid 2014: odor discrimination

Answer 10

selected 128 odor molecules and put together combos
-forced choice task - presented 3 vials and ID which is different from other 2
at 96.67 % overlap - people were still better than chance

Question 11

Lain 1979 : odor identification

Answer 11

naming what you are smelling
-P’s presented with commonly encountered ‘ecologically valid’ odours - orange, bologna etc
avg. 36/80 correct - 45%
with training and feedback - can improve to 93.6%
can be attributed to lack of practice of using odor alone

Question 12

olfactory quality

Answer 12

hard to describe and organize odors - no clear olfactory space similar to colour space
molecular structures - similar structures can have different smells

Question 13

olfactory mucosa

olfactory receptor neurons (ORNs)

Answer 13

-on the roof of nasal cavity, molecules reach it through nostrils or from oral cavity of mouth via pharynx (retro-nasal path)
-inside olfactory mucosa, transduce odorants into neural signals
each orn contains one type of receptor
10,000 orns and 400 types = 4 mil orns

Question 14

olfactory bulb

recognition profiles

Answer 14

all 10,000 orns for a receptor type project to 1-2 golmeruli (in olfactory bulb)
odorants are coded by patterns of activation of olfactory receptors - any odorant activates multiple olfactory receptors
molcules with similar stucture but different smell have different recognition patterns

Question 15

olfactory pathway

Answer 15

olfactory mucosa - smells transduced to neural signals
olfactory bulb
piriform cortex - primary olfactory cortex
orbitofrontal PFC - secondary olfactory
amygdala

Question 16

oral capture

multimodal integration of taste and smell

Answer 16

smelling foods while eating

-connections between insula and orbtiofrontal and amygdala - interactive networks and helps construct flavour

Question 17

exteroception

interoception

Answer 17

perceiving external position motion and state of body

-perceiving internal state of organs

Question 18

balance and vestibular system

Answer 18

-semicircular canals - 3 orthoganal canals, each contain an ampule with hair cells that detect angular acceleration
otolithic organs - utricle and saccule, contains hair cells that detect linear acceleration

Question 19

circadian clock
striatal clock
hippocampal clock

Answer 19

• keeps track of days, located in suprachiasmatic nucleus of hypothalamus, receives input from intrinsically photosensitive retinal ganglion cells - overall light
• keeps track of short intervals (sec), keeping a beat, involves motor control circuitry of cortico-basal-ganglia-thalamo-cortical loops
• keeps track of minutes and hours -episodic memory system