physiology of taste and smell

Question 1

what are taste and smell recognised by?

Answer 1

chemoreceptors

Question 2

where is taste sensed by?

Answer 2

chemoreceptors packaged into taste buds - sense organs of taste

Question 3

what do taste buds consist of?

Answer 3

sensory receptor cells and support cells arranged like slices of orange

Question 4

how long is the lifespan of taste receptors and what are they replaced by?

Answer 4

10 days
basal cells in taste buds

Question 5

where are taste buds located?

Answer 5

tongue
palate
epiglottis
pharynx

Question 6

where do the majority of tastebuds sit?

Answer 6

papillae of tongue

Question 7

what are the 4 types of papillae?

Answer 7

filliform - most, only one that does NOT contain taste buds
fungiform
vallate
foliate
rest contain taste buts

Question 8

what is the first step in the process of taste?

Answer 8

binding of taste provoking chemical (tasant) to receptor cells produces depolarising receptor potential

Question 9

what is the second step in process of taste?

Answer 9

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

Question 10

what is the third stage in process of taste?

Answer 10

signals conveyed by cranial nerves via brainstem and thalamus to cortical gustatory areas

Question 11

what is the fourth stage in process of taste?

Answer 11

afferent taste fibres reach brainstem via cranial nevres

Question 12

which cranial nerve is responsible for afferent taste fibres reaching anterior 2/3 of tongue?

Answer 12

CN VII chorda tympani branch of facial nerve

Question 13

which cranial nerve is responsible for afferent taste fibres reaching posterior 1/3 of tongue?

Answer 13

CN IX

Question 14

which cranial nerve is responsible for afferent taste fibres reaching areas other than tongue including epiglottis and pharynx?

Answer 14

CN X

Question 15

what are the 5 primary tastes?

Answer 15

bitter
sour
salty
sweet
umami (meat or savoury)

Question 16

what is bitter taste stimulated by?

Answer 16

diverse group of tastants incl. alkaloids, poisonous substances and toxic plant derivatives

Question 17

what is sour taste stimulated by?

Answer 17

acids which contain free H+ ions

Question 18

what is salty taste stimulated by?

Answer 18

chemical salts, esp. sodium chloride (NaCl)

Question 19

what is sweet taste stimulated by?

Answer 19

configuration of glucose

Question 20

what is umami taste triggered by?

Answer 20

amino acids especially glutamate

Question 21

what is aguesia?

Answer 21

loss of taste function

Question 22

what can cause aguesia?

Answer 22

nerve damage
local inflammation
endocrine disorders

Question 23

what is hypogeusia?

Answer 23

reduced taste function

Question 24

what can cause hypogeusia?

Answer 24

chemo
meds

Question 25

what is dysgeusia?

Answer 25

distortion of taste function

Question 26

what can cause dysgeusia?

Answer 26

glossitis gum infections tooth decay reflux chemo neoplasms zinc deficiencyw

Question 27

what cranial nerve mediates common odours?

Answer 27

main olfactory nerve CN I

Question 28

which cranial nerve helps to halt inhalation if you sniff something harmful to protect the lungs?

Answer 28

trigeminal somatosensory system CN V

Question 29

where does the olfactory cleft sit?

Answer 29

about 7cm into nasal cavity from the nostril

Question 30

what is olfactory cleft composed of?

Answer 30

cribiform plate small parts of superior and middle turbinate and septum

Question 31

which cells is the olfactory neuroepithelium composed of?

Answer 31

pseudostratified columnar epithelium

Question 32

what does the duct cell of Bowmans glands secrete?

Answer 32

mucus

Question 33

what do axons of olfactory receptors collectively form?

Answer 33

olfactory nerve

Question 34

what is the first stage in the process of smell?

Answer 34

smell detected by olfactory receptors within the olfactory neuroepithelium

Question 35

what is the second stage in the process of smell?

Answer 35

binding of odour molecules to olfactory receptors initiates a signal transduction cascade that converts olfactory stimuli into neural signals (glutamate and dopamine)

Question 36

what is the third stage in process of smell?

Answer 36

axons of olfactory receptors assemble into bundles of olfactory nerves, which penetrate the small foramina in the cribriform plate of the ethmoid bone and enter the cranial cavity

Question 37

what is the fourth stage in the process of smell?

Answer 37

once in the cranial cavity the fibres enter olfactory bulb that lie in olfactory groove within anterior cranial fossa

Question 38

what is the fifth stage in process of smell?

Answer 38

olfactory bulb transmit smell info to brain

Question 39

what is the sixth stage of process of smell?

Answer 39

from olfactory bulb neurons pass along olfactory tract to reach each temporal lobe and olfactory areas

Question 40

what does a substance need in order to be smelled?

Answer 40

volatile + water soluble

Question 41

what must an odourant do before neural conduction can occur from olfactory cleft to brain?

Answer 41

enter nose during active (sniffing) or passive (diffusion) process pass to olfactory cleft move from air phase to aqueous phase

Question 42

what is the role of mucus?

Answer 42

moist and protect environment aid is dispersing odourants to olfactory receptors from the mucous odourants either diffuse or are transported by specialised proteins to receptors

Question 43

what is anosmia?

Answer 43

inability to smell

Question 44

what is hyposmia?

Answer 44

reduced ability to smell

Question 45

what is dysosmia?

Answer 45

altered sense of smell

Question 46

what is phantosmia?

Answer 46

smell perceived in absence of stimulus

Question 47

what are conductive causes of abnormalities in smell?

Answer 47

nasal polyps rhinitis nasal mass

Question 48

what are sensironeural causes in abnormalities in smell?

Answer 48

viral (cold, COVID) head trauma neuro conditions brain tumours meds