chemical senses (olfaction & gustation) Flashcards
where are primary sensory neurons for olfaction located?
epithelial lining of nasal cavity
how do cilia protect nasal cavity?
by forming a mesh
how do odorants act on cilia receptors?
odorant binds to gpcr
adenylyl cyclase activated to convert atp to cAMP
cyclic nucleotide gated channel activated
Na+ and Ca2+ influx = depolarisation
how do we differentiate smells?
(and what part of the ____)
each different odorant binds to a different receptor = different smell
variable amino acids within binding pocket allows for different binding site for different odorants
are olfactory lipo/hydrophilic
typically lipophilic
process of adapting to odours in the environment
(2 enzymes & the processes)
O-P450 & UGT: turn lipophilic odour into hydrophilic INACTIVATING the signal
Calcium influx inhibits cAMP production -> channels close -> inhibited
CO: can have inhibiting affects
what is concentration of odour coded by?
frequency of action potentials
what role does chlorine have in olfaction?
Cl- efflux is activated by Ca2+ influx
This further depolarises the neuron -> SHARPENING the olfaction
what are the three cell types for olfaction
granule cells, mitral cells, tufted cells
granule cells
inhibitory neurons within olfactory bulb
sharpen sensation to a particular smell
influence firing of mitral cells
olfactory bulb layers
glomerular layer
external plexiform layer
mitral cell layer
internal plexiform layer
granule cell layer
lateral inhibition (olfaction)
granule cells suppress adjacent mitral cells to sharpen sensory info from the 1 mitral cell
where does the olfactory bulb project to?
pyriform cortex , olfactory cortex , amygdala , entorhinal cortex
amygdala & olfaction
connects smell to ans
emotional connection to smell
entorhinal cortex & olfaction
to hippocampus
memory
are gustation chemicals lipo/hydrophilic & why?
hydrophilic
chemicals must be dissolved in saliva to reach taste buds in crevice of papillae
taste buds
have receptors for each 5 types of tastes, just in different strengths
papillae
(why and what type of receptors?)
bumps on tongue increases SA and friction (grip food)
most dont have taste receptors, sense texture
TRC
not neurons , receptor cells!
labelled line model (trcs)
primary neuron only attuned to 1 taste
across fibre models (trcs)
- receptor sens to range, depends on a.p.
- trc’s selective but signal to all neurons
what flavours use gcpr channels?
umami sweet and bitter
what flavours use tpr?
sour
(salt and acids)
what type of receptors are taste receptors
heterodimers
composed of two parts, both need to be there for the taste
why does age change taste perception?
salt receptors regulated by aldosterone, this fluctuates with age, therefore changing taste perception with age
why does vibration of plane inhibit taste?
gustation pathways pass through auditory canal
pathway of gustation to brain
taste buds (via cranial nerves 7,9,10) -> NSC -> hypothalamus, amygdala
olfaction & gustation cross where?
priform cortex, insula before going to amygdala
