Physiology of Taste and Smell

Question 1

What kind of sensations are induced by smell recpetors?

Answer 1

Pleasurable or objectionable

Question 2

What is the purpose of taste and smell receptors?

Answer 2

1. Checkpoint for quality control (most poisons taste bitter, off foods smell bad, sour taste acidic)
2. Influences flow of digestive juice
3. Taste influenced by information from smell

Question 3

What are taste buds?

Answer 3

Package of sensory receptor cells of taste

Question 4

Taste buds consist of sensory receptor cells and support cells arranged like _____

Answer 4

slices of orange 🍊

Question 5

What is the average life span of taste receptor cells?

Answer 5

10 days

Question 6

Where are taste receptor cells replaced from?

Answer 6

Basal cells within taste buds

Question 7

Where are taste buds present?

Answer 7

Tongue, palate, epiglottis and pharynx

Question 8

Majority of taste buds sit in ___ in the tongue

Answer 8

Papillae

Question 9

What are papillae?

Answer 9

Papillae are finger-like structures which give rise to the rough appearance of the dorsum of the tongue

Question 10

What are the types of papillae present in tongue?

Answer 10

FIliform, fungiform, foliate, vallate

Question 11

Which papillae does not contain taste buds?

Answer 11

FIlliform

Question 12

Binding of tastant to receptor cells produces ____

Answer 12

Depolarising receptor potential

Question 13

Taste signals conveyed by cranial nerves via brainstem and thalamus go to___?

Answer 13

Cortical gustatory areas

Question 14

Afferent taste fibres reach the brainstem via which nerves?

Answer 14

1. CN VII (ant. 2/3rds of the tongue)
2. CN IX (pos. 1/3rd of the tongue)
3. CN X (epiglottis, pharynx)

Question 15

What are the 5 primary tastes?

Answer 15

Bitter
Sweet
Salty
Umami

Question 16

What stimulates bitter sensation of taste?

Answer 16

alkaloids, poisonous substances, toxic plant derivatives

Question 17

What stimulates sour sensation of taste?

Answer 17

acids which contain free H+ ions

Question 18

What stimulates sweet sensation of taste?

Answer 18

configuration of glucose

Question 19

What stimulates salty sensation of taste?

Answer 19

chemical salts (especially NaCl)

Question 20

What stimulates umami sensation of taste?

Answer 20

amino acids (especially glutamate)

Question 21

What are some abnormalities of taste?

Answer 21

Aguesia (loss of taste)
Hypoguesia (reduced taste)
Dysgeusia (distortion of taste)

Question 22

What causes Ageusia

Answer 22

nerve damage,
local inflammation(glossitis, radiation, tobacco)
some endocrine disorders

Question 23

What causes Hypogeusia

Answer 23

chemotherapy, medications

Question 24

What causes Dysgeusia

Answer 24

glossitis, gum infections, tooth decay, reflux, URT, medications, neoplasms, chemotherapy, Zn deficiency

Question 25

What are the 4 neural systems within the nose?

Answer 25

Main olfactory system (CN I)
Trigeminal somatosensory system( CN V)
Accessory olfactory system (the vomernasal)
The nervus terminalis

Question 26

What type of olfactory function is CN I involved in?

Answer 26

common odours (rose, chocolate, vanilla)

Question 27

What type of olfactory function is CN V involved in?

Answer 27

chemical and non-chemical stimulus (irritation, burning, cooling, tickling)
protective effect (halting inhalation after sniffing something harmful)

Question 28

What is olfactory cleft?

Answer 28

Small region of nasal mucosa where olfactory neuroepithelium exists

Question 29

What are the structures making up the olfactory cleft?

Answer 29

Cribriform plate
Very small parts of superior an d middle turbinate and septum

Question 30

How is smell added to taste while swallowing foods?

Answer 30

When there is retrograde airflow from the nasopharynx during swallowing of food

Question 31

How is quiet breathing different from sniffing?

Answer 31

Quiet breathing -> odorants reach smell receptors by diffusion (as olfactory mucosa is above the normal path of airflow)

Sniffing -> enhanced smelling by drawing air currents upwards within nasal cavity

Question 32

What features must a substance have for it to be smelled?

Answer 32

(1) sufficiently volatile i.e. some of its molecules can enter the nose with inspired air
(2) sufficiently water-soluble i.e. can dissolve in the mucus coating of olfactory mucosa

Question 33

Why is mucus important in olfaction?

Answer 33

1)Moist and protective environment.
2)Aids in dispersing odourants to the olfactory receptors.
3)From the mucus odourants either diffuse or are transported by specialised proteins to the receptors

Question 34

What type of epithelium composes olfactory neuroepithelium?

Answer 34

pseudostratified columnar epithelium

Question 35

What are the cells present in olfactory neuroepithelium?

Answer 35

1) Bi-polar sensory (afferent) neurones
2) Basal cells (stem cells)
3) Supporting cells
4) Duct cells of Bowman’s gland

Question 36

Which cells produce mucus within the olfactory neuroepithelium?

Answer 36

Duct cells of Bowman’s gland

Question 37

What are olfactory receptors?

Answer 37

Specialised ENDINGS of RENEWABLE afferent neurons

Question 38

Axons of olfactory receptors collectively form what?

Answer 38

afferent fibres of olfactory nerve

Question 39

From the olfactory bulb, neurons pass along the olfactory tract to reach ____ and ____

Answer 39

Temporal lobe and olfactory areas

Question 40

What are the abnormalities in smell?

Answer 40

Anosmia
Hyposmia
Dyosmia
Phantosmia

Question 41

What are the causes of abnormalities in smell?

Answer 41

1.Conductive (nasal polyps, rhinitis, nasal masses)
2. Sensorineural (viral, head trauma, neurological conditions, brain tumours, medication)