The Chemical Senses

Question 1

What is a potential function of taste?

Answer 1

Gatekeeper to body to identify what is okay to be ingested

Question 2

!!Evolutionary aspects of the 5 tastes

Answer 2

Sugar - high calorific value/energy
Bitter - could be poisonous
Salty-
Sour

Question 3

How is taste information encoded in taste cells?

Answer 3

Embedded in our papillae - our taste buds. There are receptors that correspond to the tastant

Question 4

Labelled line Model of Taste

Answer 4

Each cell is specialized for one of the tastants. The signals picked up by each cell will be sent separately/through seperate neurons to the brain

Question 5

Across fibre model of taste

Answer 5

A taste cell is not specilized for one of the 5 specific tastes, it responds to all the different taste qualities. The code for a particualr quality is determined by the pattern of activity across all of the afferent nerve fibres rather than by the actiivty in any single nerve fibre

Question 6

Transduction in taste reception

Answer 6

Lock and key model- a tastant fits a certain receptor which open ion channels, depolarozes the cell and chemical transduction happens, sending signal to gustatory nerves

Question 7

Name the typical tastants for each taste

Answer 7

Sugar - glucose, fructose
Sour - acid –> citric, or acetic
Bitter - quanine (tonic water) or caffeine
Salty - sodium chloride
Umami - monosodium glutamate (MSG)

Question 8

What is the taste pathway

Answer 8

Signals from the taste cells travels along the nerve and make conneciton with the Nucleus of Solitary Tract (in brain stem). From there goes to hypothalamus, amygdala, and OrbitoFrontal Cortex (where smell and taste meet)

Question 9

What is Anosmia?

Answer 9

Like blindness - loss of sight or deafness - loss of hearing
Anosmia - loss of smell

Question 10

What thresholds can be used to measure smell?

Answer 10

Detection Threshold -for different concentrations
Recognition Threshold - recognizing rather than detecting a smell

Question 11

What is the interaction between labelling a smell and identifying a smell?

Answer 11

if you can give the smell a name its often also easier to detect

Question 12

What is an Olfacometer and what can it be used for?

Answer 12

it is an instrument used to detect and measure odor dilution
The olfactometer helps to control airflow and humidity

Question 13

Name the key constituents of the olfactory system?

Answer 13

Nasal cavity/passage
Olfactory Receptor Neurons (ORNs)
Olfactory bulb
Glomerulli

Question 14

!!What is ORN in olfaction?

Answer 14

Olfacotry Receptor neuron responsible for
There are about 350 different ones in humans and 10000 of each class, so can be 4 million each, though varies depending on source. Output of an ORN will only go to one or two glomeruli in olfactory bulb. Violates the principle of graceful degradation - if you lose a nerve cuz of accident youre losing sense of smell

Question 15

Describe the olfactory pathway

Answer 15

Signal form the olfactory bulb travels to the primary olfaxctory cortex (PC) and amygdala. Then passes the OrbitoFrontal Cortex aka secondary olfactory cortex, which is where smell and taste meet

Question 16

Explain olfactory encoding, comparing it to the cones in the visual system

Answer 16

Different odorants cause different neural activity across a range of olfactory classes, like how the L,S, and M cones are activated different based on wavelengths. Except in this case there are 350 differents types of ORNs rather than just three. Though there are way more in the olfactory system, in practice, many of these arent actually active

Question 17

What is the difference between flavor and taste?

Answer 17

Taste concerns the 5 tastes (sweet, sour….) whereas flavour refers to the combinaton of taste and smell - its a multisensory percept. Flavor perception is impacted when nose is blocked, because a lot of flavor comes from the retronasal route, and without airflow the chemicals/gasses dont reach it

Question 18

Explain the physiology of Flavor

Answer 18

The Orbitofrontal Cortex (OFC) is the first place where smell and taste combines.

Question 19

Name the different aspects of flavor, other than smell

Answer 19

Taste :
-Aftertaste
-Intensity
-Quality (sweet, sour, bitter…)
-Hedonics (is a pleasant kind of sour, is it strong…)

Vision : does it look appealing

Hunger/Thirst

“Mouth feel” : texture, coolness,..)