Physiology of taste and smell

Question 1

What is the organ of taste?

Answer 1

Taste buds

Question 2

What makes up a taste bud?

Answer 2

Sensory receptor cells and support cells

Question 3

What is the life span of a taste receptor cell?

Answer 3

10 days

Question 4

Where can taste buds be found?

Answer 4

Tongue, palate, epiglottis and pharynx

Question 5

What are the 4 types of papillae?

Answer 5

Filiform
Fungiform
Vallate
Foliate

Question 6

What papillae does not contain taste buds?

Answer 6

Filiform

Question 7

How is taste generated?

Answer 7

Binding of tastant (chemical) to receptor cells alters cell ionic channels and produces depolarisation receptor potential
Signal conveyed by cranial nerves via brainstem and thalamus to the cortical gustatory areas

Question 8

What cranial nerves are involved in taste?

Answer 8

Chorda tympani - branch of facial nerve supplies anterior 2/3rd of tongue
Glossopharyngeal supplies posterior 1/3rd of tongue
Vagus nerve supplies epiglottis and pharynx

Question 9

What are the 5 primary tastes?

Answer 9

Salty
Sour
Sweet
Bitter
Umami

Question 10

What stimulates salty gustation?

Answer 10

NaCl

Question 11

What stimulates sour gustation?

Answer 11

Acids that contain H+

Question 12

What stimulates sweet gustation?

Answer 12

Glucose

Question 13

What stimulates bitter gustation?

Answer 13

Diverse group of tastants including alkaloids, poisonous substances and toxic plant derivatives

Question 14

What stimulates umami gustation?

Answer 14

Amino acids, especially glutamate

Question 15

What is anguesia and what can call it?

Answer 15

Loss of taste
Nerve damage, local inflammation (glossitis, radiation, tobacco)
Endocrine disorders

Question 16

What is hypogeusia and what can cause it?

Answer 16

Reduced taste function
Chemo
Mediations

Question 17

What is dysgeusia and what can cause it?

Answer 17

Distortion of taste

Glossitis, gum infections, tooth decay, reflux, URTI, medications, neoplasms, chemo, zinc deficiency

Question 18

What are the 3 types of olfactory cells?

Answer 18

Olfactory receptor cells
Supporting cells
Basal cells (secrete mucosa)

Question 19

Where can olfactory receptor cells be found?

Answer 19

Patch of mucosa in the ceiling (dorsal roof) of the nasal cavity

Question 20

What is special about olfactory receptors?

Answer 20

Specialised endings or RENEWABLE afferent neurones

Question 21

How is smell transmitted?

Answer 21

Olfactory neurones has a thick short dendrite and an olfactory rod
The cilia of olfactory rod will project into olfactory mucosa (10-12 per neurone)
Odorants bind to the cilia
Axons form afferent fibres of olfactory nerve which pierce the cribriform plate of the ethmoid bone to enter the olfactory bulb in the interior surface of the brain
Olfactory bulb passes AP along olfactory tract to the temporal lobe and olfactory areas

Question 22

What is the life span of an olfactory receptor?

Answer 22

2 months

Question 23

How are new olfactory receptors produced?

Answer 23

Basal cells

Question 24

How do odorants reach the olfactory mucosa in quiet breathing?

Answer 24

Diffusion as the olfactory mucosa is above the normal path of airflow
Sniffing will enhance smell

Question 25

What properties must a substance have to be smelled?

Answer 25

Sufficiently volatile - enter the nose with inspired air

Sufficiently water soluble - dissolve in the mucous coating of olfactory mucosa

Question 26

What is anosmia and what can cause it?

Answer 26

Inability to smell

Viral infections, allergy, nasal polyps, head injury

Question 27

What is hyposmia and what can cause it?

Answer 27

Reduced ability to smell

Early sign of parkinson’s disease

Question 28

What is dysosmia and what can cause it?

Answer 28

Altered sense of smell
Differently interpreting some odors
Hallucinations of smell