Physiology of Taste and Smell

Question 1

What type of receptors are responsible for taste and smell?

Answer 1

chemoreceptors

Question 2

Taste perception can be influenced by smell receptors. TRUE/FALSE?

Answer 2

TRUE

Question 3

What are the two main types of cell found in the taste buds?

Answer 3

sensory receptor cells

and support cells

Question 4

What cells regenerate the receptor cells, and after how long?

Answer 4

replaced from basal cells

after about 10 days (lifespan)

Question 5

What type of nerve fibres are present behind the taste buds to rely information to the brain?

Answer 5

afferent nerve fibres

Question 6

Where are taste buds mainly present?

Answer 6

tongue
palate
epiglottis
pharynx

Question 7

Where are taste buds found in the tongue?

Answer 7

In papillae

Question 8

What are the four types of papillae found on the tongue?

Answer 8

Filliform
Fungiform
Vallate
Foliate

Question 9

What type of papillae do NOT contain taste buds?

Answer 9

Filliform

mostly found at tip of tongue - are sensitive to touch and temp

Question 10

How do APs arise in the afferent nerve fibres behind the taste buds?

Answer 10

Tastants bind to receptor cells
Depolarise membrane
Fire AP

Question 11

Where are taste signals processed in the brain?

Answer 11

cortical gustatory areas

Question 12

What cranial nerves are involved in afferent signals of taste reaching the brainstem?

Answer 12

CN VII - chorda tympani = anterior 2/3 of the tongue

CN IX = posterior 1/3 of the tongue

CN X = areas other than tongue, e.g. epiglottis and pharynx

Question 13

What are the 5 primary tastes?

Answer 13

Salty
Sour
Sweet
Bitter
Umami (meaty or savory)

Question 14

What chemical compound provokes a salty taste?

Answer 14

NaCl

Question 15

What chemical provokes a sweet taste?

Answer 15

Glucose or a configuration of glucose

Question 16

What ion is responsible for sour tasting food?

Answer 16

H+

Question 17

What substances cause a bitter taste in the mouth?

Answer 17

diverse group of tastants:

• alkaloids
• poisonous substances
• toxic plant derivatives

Question 18

Umami taste is provoked by what chemical compound?

Answer 18

amino acids especially glutamate

Question 19

What is the difference between Ageusia, Hypogeusia and Dysgeusia?

Answer 19

Ageusia (loss of taste function)
Hypogeusia (reduced taste function)
Dysgeusia (distortion of taste function

Question 20

What can cause ageusia?

Answer 20

• nerve damage
• local inflammation (e.g. glossitis, radiation, tobacco)
• some endocrine disorders

Question 21

What can cause hypogeusia?

Answer 21

chemotherapy

medications

Question 22

What can cause dysgeusia?

Answer 22

glossitis
gum infections/tooth decay
reflux
URTI
medications/chemotherapy
neoplasms
zinc deficiency

Question 23

What are the 3 cell types found in the olfactory mucosa?

Answer 23

olfactory receptor cells
supporting cells
basal cells

Question 24

What are olfactory receptors?

Answer 24

specialised endings of renewable afferent neurons

Question 25

How do the neurons of olfactory receptors appear?

Answer 25

thick short dendrite and an expanded end called an olfactory rod

Question 26

What part of the olfactory nerve pierces the cribriform plate of the ethmoid bone to enter the olfactory bulbs in the brain?

Answer 26

Axons of olfactory receptors collectively form afferent fibres of olfactory nerve which pierce the ethmoid bone

Question 27

After reaching the olfactory bulb, where are signals transmitted to perceive a smell?

Answer 27

neurons passes along the olfactory tract to reach temporal lobe and olfactory areas

Question 28

Why is quiet breathing less efficient for perceiving smells?

Answer 28

olfactory mucosa is above the normal path of airflow => During quiet breathing odorants only reach smell receptors by diffusion

Question 29

What are the 2 factors which enhance the ability to smell a substance?

Answer 29

Substance is sufficiently volatile It is sufficiently water soluble => i.e. can dissolve in the mucus coating of olfactory mucosa

Question 30

WHat is the difference between anosmia, hyposmia and dysosmia?

Answer 30

Anosmia (inability to smell): Hyposmia (reduced ability to smell): Dysosmia (altered sense of smell)

Question 31

WHat causes anosmia and hyposmia?

Answer 31

viral infections allergy nasal polyps head injury **Hyposmia may be early sign of Parkinson's disease**

Question 32

What is caused in dysosmia?

Answer 32

differently interpreting some odours | hallucinations of smell