The Chemical Senses

Question 1

what are 3 functions of the chemical substances?

Answer 1

identifying food sources,
avoiding noxious substances,
finding a mate or marking territories.

Question 2

what are the 5 basic tastes?

Answer 2

salt,
sweet,
sour,
bitter,
umami.

Question 3

explain salty tastes:

Answer 3

salts are vital electrolytes,
ionotropic receptors in receptor cells detect salty tastes,
it is a craved taste.

Question 4

explain sweet tastes:

Answer 4

we have an innate fondness,
they are usually of high energy foods,
detected by metabotropic receptors in taste receptor cells.

Question 5

explain sour tastes:

Answer 5

usually of food with high H+ concentrations / acidic foods,
they are aversive to us,
ionotropic receptors detect these tastes in receptor cells.

Question 6

explain bitter tastes:

Answer 6

instinctively rejected,
often poisons,
we can adapt to like these flavours,
metabotropic receptors in receptor cells detect these tastes.

Question 7

explain umami tastes:

Answer 7

the savoury taste of glutamate,
it is a taste that is craved,
it is detected by metabotropic receptors in the receptor cells.

Question 8

what tastes are detected by metabotropic receptors?

Answer 8

sweet,
bitter,
umami.

Question 9

what tastes are detected by ionotropic receptors?

Answer 9

salt,

sour.

Question 10

what is the lingual papillae?

Answer 10

area on the tongue where we find our taste buds.

Question 11

what about the lingual papillae on the back of the tongue?

Answer 11

these are larger and called circumvallate papillae.

Question 12

what are circumvallate papillae?

Answer 12

are ridges and folds at the back of the tongue containing taste buds.

Question 13

what about lingual papillae at the edges of the tongue?

Answer 13

these aren’t as large, but there are foliate papillae and fungiform papillae.

Question 14

what are foliate papillae?

Answer 14

ridges and folds at the edges of the tongue containing taste buds.

Question 15

what are fungiform papillae?

Answer 15

projections at the edges of the tongue containing taste buds.

Question 16

why is there more taste detection at the back of the tongue? (simple answer)

Answer 16

there are more taste buds there.

Question 17

how is the glossopharyngeal nerve (cranial nerve 9) involved in taste?

Answer 17

it carries information about taste at the back of the tongue to to the brain.

Question 18

how is the chorda tympanic nerve (cranial nerve 7) involved in taste?

Answer 18

it carries info from foliate and fungiform papillae on side and front of the tongue to the brain.

Question 19

how do chemicals enter the taste bud?

Answer 19

through the taste pore.

Question 20

explain what this means: the taste receptor cells are polarised.

Answer 20

the apical portion (top) has microvilli where transduction occurs,
signals move down to the basal portion (bottom) where neurotransmitter is released onto gustatory afferents.

Question 21

what are the membranous receptors that detect salty and sour tastes?

Answer 21

ion channels - ENaC for salty and OTOP1 and proton channels for sour.

Question 22

what are the membranous receptors that detect sweet, bitter, and umami tastes?

Answer 22

G-protein coupled receptors - T1R2 and T1R3 for sweet, T2Rs for bitter, and T1R1 and T1R3 for umami.

Question 23

how many types of stimuli do taste cells respond to?

Answer 23

only 1 - they are specific.

Question 24

how many stimuli do taste buds respond to?

Answer 24

they contain taste cells which respond to various stimuli.

Question 25

gustatory afferents are separate to taste cells meaning what?

Answer 25

it requires neurotransmitter release across synaptic cleft.

Question 26

basically describe how the olfactory system detects scents:

Answer 26

odorant molecules enter the nasal cavity and diffuse into mucus surrounding the olfactory epithelium,
this is connected to the olfactory bulb,
which connects to the olfactory cortex.

Question 27

where are the cilia of the olfactory receptor cells found?

Answer 27

they project into the mucus, and the axonal section projects into the olfactory bulb.

Question 28

explain how the olfactory receptor cells are bipolar chemoreceptive neruons:

Answer 28

odorants dissolve in the mucus layer,
transduction machinery in the cilia on the dendrites convert these molecules into electrical signals,
the primary afferent is the olfactory receptor cell axon.

Question 29

what specifically detects odorants?

Answer 29

odorant receptor proteins ORs.

Question 30

what type of receptors are odorant receptor proteins?

Answer 30

G-protein coupled receptors.

Question 31

what happens if olfactory receptor cells express the same olfactory receptor proteins?

Answer 31

they converge on to the glomerulus in the olfactory bulb.

Question 32

what does convergence in the olfactory enable?

Answer 32

enables low concentration of odorants to be detected.

Question 33

what does convergence in the olfactory enable?

Answer 33

enables low concentration of odorants to be detected.

Question 34

despite the replacement of olfactory receptor cells, each glomerulus…

Answer 34

each glomerulus will continue to be associated with the same odorant.

Question 35

second order neurons carry info from the glomerulus to various parts of the brain:

Answer 35

olfactory cortex - conscious smell,
hippocampus - olfactory cortex,
amygdala - emotional responses,
hypothalamus,
reticular formation - visceral responses.