Chemical Senses Flashcards
What are the chemical senses?
taste
smell
What are the 5 basic tastes?
salt, sweet, sour, bitter, umami
What is the distribution of taste cells?
bits of tongue are more sensitive to some tastes but no real distribution
what are taste buds?
groups of taste cells
Where are taste buds found?
tongue, palate, pharynx
what are taste cells not?
sensory neurones (they look like a synpase but they aren’t a synapse because they have no neurone)
What happens when a chemical binds to a taste cell?
- chemical binds
- transduction occurs causing a receptor potential
- depolarisation
- voltage gated calcium channels open
- calcium entry
- neurotransmitter released
- excites sensory neurone
- action potential
How is salt detected?
- sodium entry causes depolarisation through leak channels
2. if there is a high conc of Na+ it causes an action potential
How is sour detected?
- H+ ions can either enter through TRP
- or H+ block K+ channels causing depolarisation
How are sweet, umami and bitter detected?
- G protein coupled receptors
- subunits are T1R and T2R family
- unique combination of each subunit for each taste
What is the sweet combination?
T1R2 T1R3
Umami combination?
T1R1 and T1R3
Bitter combination?
T2R T2R
What is the central taste pathway?
gustatory sensory axons
cranial nerves
brainstem
thalamus
primary gustatoty cortex
What are the secondary pathways for taste and what are they used for?
-medulla
responsible for salivation and swallowing
-hypothalamus
for satiety (fullness) palatability (how nice it is)
Where are the smells receptors?
small receptors in the olfactory epithelium
Are olfactory cells neurones?
yes
How many types of receptor does each olfactory cell have?
one
Can receptor molecules bind to more than one odourant?
yes
What is population coding?
any one neurone will detect its own unique bunch of smells
Why do you get used to cells?
because the olfactory neurone can adapt quickly to the presence of a smell
How is it transduced?
single mechanism for all receptors:
odourant binds to receptor
G protein mediated events
Intracellular cascade
Na+/Ca+ channels open
depolarisation
receptor potential
Where is the olfactory bulb?
glomerulus
What is the central olfactory pathway?
olfactory neurones
olfactory bulb
olfactory cortex
can go to either:
limbic areas (associates information e.g smell of place)
MD thalamus to orbitofrontal cortex (recognition and combining smell and taste)
