Physiology of Taste and Smell

Question 1

what type of receptors are taste and smell receptors

Answer 1

chemoreceptors - stimulated by binding to particular chemicals

stimulation induces a pleasurable/objectionable sensation

Question 2

what protectional function does taste and smell have

Answer 2

check for quality control eg poisons taste bitter, off food tastes bad

Question 3

do taste and smell influence eachother ?

Answer 3

yes, taste perception is influenced by information from smell receptors

Question 4

do taste and smell have an influence on the flow of digestive juices?

Answer 4

yes

Question 5

gustation

Answer 5

the action of tasting

Question 6

where are the sensory receptor cells of taste found

Answer 6

mainly taste buds - they are the sense organs of taste

Question 7

what is the life span of taste receptor cells

Answer 7

about ten days, they are replaced from basal cells in the taste buds

Question 8

sensation of taste and taste buds

Answer 8

taste buds consist of sensory receptor cells and support cells

the receptor cells synapse with afferent nerve fibres

Question 9

where are taste buds mainly present

Answer 9

tongue, palate, epiglottis and pharynx

Question 10

what gives the rough apperance to the dorsum of the tongue

Answer 10

papillae - contain taste buds

Question 11

Answer 11

Question 12

which papillae on the tongue are not involved in tasting

Answer 12

filliform - the most numberous, they are involved in general sensory eg touch and temperature

Question 13

tastant

Answer 13

capable of eliciting gustatory excitation e.g. stimulating the sensation of taste

Question 14

describe the stimulation of the sensation of taste

Answer 14

binding of tastant to receptor cell alters cell ionic channels and produces depoalrising receptor potential

RP initiates action potential in afferent nerve fibres which synapse with receptor cells

signals conveyed by CN via brainstem and thalamus to cortical gustatory areas

Question 15

which cranial nerves do afferent taste fibres reach the brainstem via

Answer 15

CNVII

CNIX

CNX - areas other than tongue

Question 16

what are the 5 primary tastes

Answer 16

salt

sour

sweet

bitter

umami (meaty or savoury)

Question 17

salty taste

Answer 17

stimualted by chemical salts, especially NaCl

Question 18

sour taste

Answer 18

stimulated by acids which contain free hydrogen ions

Question 19

sweet taste

Answer 19

stimulated by configuration of glucose

Question 20

bitter taste

Answer 20

stimulated by diverse group of tastants eg alkaloids, poisonous substances and toxic plant derivatives

Question 21

umami taste

Answer 21

triggered by amino acids, especially glutamate

Question 22

ageusia

Answer 22

loss of taste sensation

can be caused by eg nerve damage, local inflammation, endocrine disorders

Question 23

what is ageusia often associated with

Answer 23

anosmia

Question 24

hypogeusia

Answer 24

reduced taste function

can be caused by eg chemo and medications

Question 25

dysguesia

Answer 25

distortion of taste function can be caused by e.g. glossitis; gum infections; tooth decay; reflux; upper respiratory infections; medications; neoplasms; chemotherapy; zinc deficiency

Question 26

where is the olfactory mucosa located

Answer 26

3. ceiling of nasal cavity

Question 27

what is the function of the basal cells in the olfactory mucosa

Answer 27

secrete mucous

Question 28

which 3 types of cells does the olfactory mucosa contain

Answer 28

basal cells supporting cells olfactory receptor cells

Question 29

describe the olfactory receptor cells

Answer 29

specialised endings of renewable afferent neurones each neuron has a thick short dendrite and an expanded end known as an **olfactory rod** **cilia** project from the olfactory rod onto the surface of the olfactory mucosa (mucus layer) **odorants** bind to the cilia

Question 30

what is the lifetime of olfactory receptors

Answer 30

2 months - basal cells act as precursors for new olfactory receptor cells

Question 31

Answer 31

Question 32

how are different odours discriminated between

Answer 32

olfactory receptors have different sensitivity to different substances

Question 33

what is the purpose of sniffing (olfaction)

Answer 33

during quiet breathing odourants only reach smell receptors by diffusion as the olfactory mucosa is above the normal path of airflow sniffing enhances smelling by drawing air upwards within the nasal cavity

Question 34

what 2 things must a substance be to be smelled

Answer 34

sufficiently **volatile** to enter the nose in inspired air sufficiently **water soluble** to dissolve in the mucus coating the oflactory mucosa

Question 35

what may be an early sign fo Parkinsons disease

Answer 35

hyposmia

Question 36

causes of anosmia

Answer 36

viral infections, allergy , nasal polyps, head injurt

Question 37

examples of dysosmia

Answer 37

differently interpreting some odours and hallucinations of smell