L06: Taste And Smell Flashcards
What are the receptors that detect chemical called
Chemoreceptors
What chemical does chemoreceptors detect
Chemical outside the body
Why is it important that we can detect chemical
To avoid toxins and poisons
What does anosmia mean
Total loss of smell
What does aqeusia mean
Total loss of taste
What happens to the sensation of smell and taste as we age
Decreases
In chemotherapy why is there a loss of taste and smell
The cells that can detect smell and taste die off
What side effects do people with chemotherapy have
A metallic tast
Why is the olfactory bulb more prone to damage and results in loss of smell
The olfactory bulb sits outside the skull
What are the 5 sub modalities of taste
Salt Sour Sweet Bitter Umami (meatiness)
To detect taste what cells must have chemoreceptors
Tongue
Palate
Pharynx
GIT tract
What is the organisation of sub-modalities of taste in the tongue
Relative distribution
What does the relative distribution of taste sub-modalities in the tongue mean
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)
What is the surface of the tongue like
Has different types of ridges known as papilla
What is the surface of the papilla covered by
Taste buds
What are the 3 aspects of taste buds
Taste cells
Basal cells
Sensory afferents
Are taste cells sensory neurones
No
If taste cells are not sensory neurones what does this mean in terms of AP
They cannot produce AP
If taste cells cannot produce AP how do they produce a signal
They are closely associated with sensory afferents (almost ‘synapse’ with them)
Where are new taste cells born from
Basal cells
How do taste cells detect chemical/taste
Vie receptors on the taste cells that acts as chemoreceptors
How does a taste that picks up taste able to convert it to a message in sensory afferents in general
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
What differs in this general process that allow to detect sub modalities of taste
Transduction process for each sub modality differs
How does transduction occur for salt taste
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
What ion are sour food high in
Hydrogen ions
How does transduction in sour taste occur
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
How does transduction for sweet, umami and bitter occur
1) sweet, bitter and umami bind to GCPRS on taste cells
2) activation of GCPRs result in membrane depolarisation
If sweet, bitter and umami have the same transduction methods how do we distinguish between these different tastes
GCPRs are a family of subunits, depending on the subunits depends on what it detects
Which subunit family is involved in taste
T1R
T2R
Which subunits allow the detection of sweet
T1R2
T1R3
What subunits allow the detection of umami
T1R1
T1R3
Which subunits allow the detection of bitter
T2R
T2R
How many submodality taste does one indiviual taste cell detect
Only one
What is the structure of neurones in the sensory system of for taste
1st order neurone/ primary neurone
Second order neurone
Third order neurone - that goes to brain.
What are the types of primary neurone for taste in the tongue
Cranial nerve 7
Cranial nerve 9
Cranial nerve 10
Where does cranial nerve 7 detect the taste
Front of tongue
Where does cranial nerve 9 detect taste
Back of Tongue
What does cranial nerve 10 detect the taste from
Epiglottis
Describe the pathway from the tongue to the brain in the sensory/ascending system
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
Where is the gustatory cortex located
Deep figure between parietal and temporal lobe
What happens at the gustatory cortex
Primary cortical neurones compare all the inputs and determine what is being detected in the tongue
Why does the cortex compare the taste
Food has a combination of tastes
What structure gives a sensation of fullness
Hypothalamus
As humans do we have greater sensitivity to smell or taste
Smell
Where are the location of smell receptors
In the nose at the olfactory epithelium
In the olfactory epithelium where does the chemicals in the air dissolve at
Mucus layer
What cells at the olfactory epithelium detect smell
Cilia of the olfactory cells
What structure does cilia of olfactory epithelium pierce through to get into the nose
Cribriform plate
What are the cilia of olfactory cells continous with
Olfactory receptor cell
Before piercing the cribiform plate what is the structure known as
Olfactory nerve
Are cells that detect smell (olfactory cells) neurones ?
Yes as they form the olfactory nerve
If olfactory cells are neurones what does this mean in terms of AP
They can generate AP
What does the olfactory nerve go to
Olfactory bulb
How many types of chemoreceptors does each olfactory cell have
One type of chemoreceptors (similar to taste cells)
Can olfactory cells detect smell sub-modalities
No
What does each chemoreceptors bind to
A rage of smell
How do we work out what we are smelling
Via population coding
What is population coding
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
What is adaptation in olfaction
Although a stimulus is present the sensory cells do no pick it up to transmit the info
Give an example of adaptation
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
How many mechanism for all receptors are there for smell
Only one (unlike taste)
How do olfactory cells transduce a signal
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
When an AP is generated how is the info sent to the brain
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)
