L06: Taste And Smell

Question 1

What are the receptors that detect chemical called

Answer 1

Chemoreceptors

Question 2

What chemical does chemoreceptors detect

Answer 2

Chemical outside the body

Question 3

Why is it important that we can detect chemical

Answer 3

To avoid toxins and poisons

Question 4

What does anosmia mean

Answer 4

Total loss of smell

Question 5

What does aqeusia mean

Answer 5

Total loss of taste

Question 6

What happens to the sensation of smell and taste as we age

Answer 6

Decreases

Question 7

In chemotherapy why is there a loss of taste and smell

Answer 7

The cells that can detect smell and taste die off

Question 8

What side effects do people with chemotherapy have

Answer 8

A metallic tast

Question 9

Why is the olfactory bulb more prone to damage and results in loss of smell

Answer 9

The olfactory bulb sits outside the skull

Question 10

What are the 5 sub modalities of taste

Answer 10

Salt 
Sour 
Sweet 
Bitter 
Umami (meatiness)

Question 11

To detect taste what cells must have chemoreceptors

Answer 11

Tongue
Palate
Pharynx
GIT tract

Question 12

What is the organisation of sub-modalities of taste in the tongue

Answer 12

Relative distribution

Question 13

What does the relative distribution of taste sub-modalities in the tongue mean

Answer 13

There are higher sensitivity to specific sub modalities of taste in the specific regions of the tongue. (Only higher sensitive not the areas that you only taste that type of submodality)

Question 14

What is the surface of the tongue like

Answer 14

Has different types of ridges known as papilla

Question 15

What is the surface of the papilla covered by

Answer 15

Taste buds

Question 16

What are the 3 aspects of taste buds

Answer 16

Taste cells
Basal cells
Sensory afferents

Question 17

Are taste cells sensory neurones

Answer 17

No

Question 18

If taste cells are not sensory neurones what does this mean in terms of AP

Answer 18

They cannot produce AP

Question 19

If taste cells cannot produce AP how do they produce a signal

Answer 19

They are closely associated with sensory afferents (almost ‘synapse’ with them)

Question 20

Where are new taste cells born from

Answer 20

Basal cells

Question 21

How do taste cells detect chemical/taste

Answer 21

Vie receptors on the taste cells that acts as chemoreceptors

Question 22

How does a taste that picks up taste able to convert it to a message in sensory afferents in general

Answer 22

1) chemical binds to receptor on taste cells
2) this leads to transduction (change in membrane potential of taste cells)
3) change in membrane potential results in voltage gate calcium channels to open
4) calcium influx occurs
5) neurotransmitters are released
6) this excited the sensory afferents and AP is produced in the sensory neurones

Question 23

What differs in this general process that allow to detect sub modalities of taste

Answer 23

Transduction process for each sub modality differs

Question 24

How does transduction occur for salt taste

Answer 24

1) taste cells detect saltiness express non-gated sodium channels (channels that are always open)
2) sodium entry causes membrane depolarisation
3) this causes voltage- gated calcium channels to open

Question 25

What ion are sour food high in

Answer 25

Hydrogen ions

Question 26

How does transduction in sour taste occur

Answer 26

1) hydrogen ions inhibit potassium channels on the taste cells 2) inhibition of potassium channels stops potassium from leaving so you get depolarisation of the membrane 3) TRP channel allow hydorgen ions to enter which also cause membrane depolarisation

Question 27

How does transduction for sweet, umami and bitter occur

Answer 27

1) sweet, bitter and umami bind to GCPRS on taste cells | 2) activation of GCPRs result in membrane depolarisation

Question 28

If sweet, bitter and umami have the same transduction methods how do we distinguish between these different tastes

Answer 28

GCPRs are a family of subunits, depending on the subunits depends on what it detects

Question 29

Which subunit family is involved in taste

Answer 29

T1R | T2R

Question 30

Which subunits allow the detection of sweet

Answer 30

T1R2 | T1R3

Question 31

What subunits allow the detection of umami

Answer 31

T1R1 | T1R3

Question 32

Which subunits allow the detection of bitter

Answer 32

T2R | T2R

Question 33

How many submodality taste does one indiviual taste cell detect

Answer 33

Only one

Question 34

What is the structure of neurones in the sensory system of for taste

Answer 34

1st order neurone/ primary neurone Second order neurone Third order neurone - that goes to brain.

Question 35

What are the types of primary neurone for taste in the tongue

Answer 35

Cranial nerve 7 Cranial nerve 9 Cranial nerve 10

Question 36

Where does cranial nerve 7 detect the taste

Answer 36

Front of tongue

Question 37

Where does cranial nerve 9 detect taste

Answer 37

Back of Tongue

Question 38

What does cranial nerve 10 detect the taste from

Answer 38

Epiglottis

Question 39

Describe the pathway from the tongue to the brain in the sensory/ascending system

Answer 39

1) primary neurone brings info into the medulla via cranial nerves (7,9,10 depending on the location of taste) 2) primary neurone synapses at gustatory nucleus at the medulla 3) second order neurone takes info to the thalamus and terminates at the ventroposterioir medial nucleus (VPM) 4) third order neurone takes into to the primary gustatory cortex

Question 40

Where is the gustatory cortex located

Answer 40

Deep figure between parietal and temporal lobe

Question 41

What happens at the gustatory cortex

Answer 41

Primary cortical neurones compare all the inputs and determine what is being detected in the tongue

Question 42

Why does the cortex compare the taste

Answer 42

Food has a combination of tastes

Question 43

What structure gives a sensation of fullness

Answer 43

Hypothalamus

Question 44

As humans do we have greater sensitivity to smell or taste

Answer 44

Smell

Question 45

Where are the location of smell receptors

Answer 45

In the nose at the olfactory epithelium

Question 46

In the olfactory epithelium where does the chemicals in the air dissolve at

Answer 46

Mucus layer

Question 47

What cells at the olfactory epithelium detect smell

Answer 47

Cilia of the olfactory cells

Question 48

What structure does cilia of olfactory epithelium pierce through to get into the nose

Answer 48

Cribriform plate

Question 49

What are the cilia of olfactory cells continous with

Answer 49

Olfactory receptor cell

Question 50

Before piercing the cribiform plate what is the structure known as

Answer 50

Olfactory nerve

Question 51

Are cells that detect smell (olfactory cells) neurones ?

Answer 51

Yes as they form the olfactory nerve

Question 52

If olfactory cells are neurones what does this mean in terms of AP

Answer 52

They can generate AP

Question 53

What does the olfactory nerve go to

Answer 53

Olfactory bulb

Question 54

How many types of chemoreceptors does each olfactory cell have

Answer 54

One type of chemoreceptors (similar to taste cells)

Question 55

Can olfactory cells detect smell sub-modalities

Answer 55

No

Question 56

What does each chemoreceptors bind to

Answer 56

A rage of smell

Question 57

How do we work out what we are smelling

Answer 57

Via population coding

Question 58

What is population coding

Answer 58

1) When chemoreceptors bind to multiple odorants they cannot tell what they are smelling 2) each chemoreceptors detects different amount of the odorants 3) info that is sent to the brain allows the brain to compare to what it is depending on the activity of pattern

Question 59

What is adaptation in olfaction

Answer 59

Although a stimulus is present the sensory cells do no pick it up to transmit the info

Question 60

Give an example of adaptation

Answer 60

When you come from outside you can smell your home but if you stay at home for ages you would not be able to smell it anymore

Question 61

How many mechanism for all receptors are there for smell

Answer 61

Only one (unlike taste)

Question 62

How do olfactory cells transduce a signal

Answer 62

1) Odorant binds to GCPRs 2) G protein mediated events 3) intracellular cascade 4) depolarisation 5) receptor potential 5) AP generated if threshold is reached

Question 63

When an AP is generated how is the info sent to the brain

Answer 63

1) 1st order neurones that detect the range of stimulus come together and synapse at the glomerulus 2) glomerulus is in the olfactory bulb 3) at the glomerulus 2nd order neurones sends axon through the olfactory tract 4) olfactory tract goes straight to the cortex 5) from the olfactory cortex info passes via thalamus to the orbito frontal cortex (allows recognition of smell) 5) from olfactory cortex info also passes to lambic areas (allows association the smell to something else)