chemical senses (olfaction & gustation)

Question 1

where are primary sensory neurons for olfaction located?

Answer 1

epithelial lining of nasal cavity

Question 2

how do cilia protect nasal cavity?

Answer 2

by forming a mesh

Question 3

how do odorants act on cilia receptors?

Answer 3

odorant binds to gpcr
adenylyl cyclase activated to convert atp to cAMP
cyclic nucleotide gated channel activated
Na+ and Ca2+ influx = depolarisation

Question 4

how do we differentiate smells?
(and what part of the ____)

Answer 4

each different odorant binds to a different receptor = different smell
variable amino acids within binding pocket allows for different binding site for different odorants

Question 5

are olfactory lipo/hydrophilic

Answer 5

typically lipophilic

Question 6

process of adapting to odours in the environment
(2 enzymes & the processes)

Answer 6

O-P450 & UGT: turn lipophilic odour into hydrophilic INACTIVATING the signal
Calcium influx inhibits cAMP production -> channels close -> inhibited
CO: can have inhibiting affects

Question 7

what is concentration of odour coded by?

Answer 7

frequency of action potentials

Question 8

what role does chlorine have in olfaction?

Answer 8

Cl- efflux is activated by Ca2+ influx
This further depolarises the neuron -> SHARPENING the olfaction

Question 9

what are the three cell types for olfaction

Answer 9

granule cells, mitral cells, tufted cells

Question 10

granule cells

Answer 10

inhibitory neurons within olfactory bulb
sharpen sensation to a particular smell
influence firing of mitral cells

Question 11

olfactory bulb layers

Answer 11

glomerular layer
external plexiform layer
mitral cell layer
internal plexiform layer
granule cell layer

Question 12

lateral inhibition (olfaction)

Answer 12

granule cells suppress adjacent mitral cells to sharpen sensory info from the 1 mitral cell

Question 13

where does the olfactory bulb project to?

Answer 13

pyriform cortex , olfactory cortex , amygdala , entorhinal cortex

Question 14

amygdala & olfaction

Answer 14

connects smell to ans
emotional connection to smell

Question 15

entorhinal cortex & olfaction

Answer 15

to hippocampus
memory

Question 16

are gustation chemicals lipo/hydrophilic & why?

Answer 16

hydrophilic
chemicals must be dissolved in saliva to reach taste buds in crevice of papillae

Question 17

taste buds

Answer 17

have receptors for each 5 types of tastes, just in different strengths

Question 18

papillae
(why and what type of receptors?)

Answer 18

bumps on tongue increases SA and friction (grip food)
most dont have taste receptors, sense texture

Question 19

TRC

Answer 19

not neurons , receptor cells!

Question 20

labelled line model (trcs)

Answer 20

primary neuron only attuned to 1 taste

Question 21

across fibre models (trcs)

Answer 21

1. receptor sens to range, depends on a.p.
2. trc’s selective but signal to all neurons

Question 22

what flavours use gcpr channels?

Answer 22

umami sweet and bitter

Question 23

what flavours use tpr?

Answer 23

sour
(salt and acids)

Question 24

what type of receptors are taste receptors

Answer 24

heterodimers
composed of two parts, both need to be there for the taste

Question 25

why does age change taste perception?

Answer 25

salt receptors regulated by aldosterone, this fluctuates with age, therefore changing taste perception with age

Question 26

why does vibration of plane inhibit taste?

Answer 26

gustation pathways pass through auditory canal

Question 27

pathway of gustation to brain

Answer 27

taste buds (via cranial nerves 7,9,10) -> NSC -> hypothalamus, amygdala

Question 28

olfaction & gustation cross where?

Answer 28

priform cortex, insula before going to amygdala