Physiology of Taste and Smell

Question 1

What kind of receptors are for taste and smell

Answer 1

Chemoreceptors

Question 2

What does stimulation of taste and smell receptors induce

Answer 2

A pleasurable or objectionable sensation

Question 3

What does taste and smell provide

Answer 3

A checkpoint for quality control

e.g. off food, poison etc.

Question 4

What does taste and smell also affect when in association with food intake

Answer 4

Flow of digestive juices

Question 5

What is taste perception influenced by

Answer 5

Information from smell receptors

Question 6

Where are the sensory receptor cells of taste located

Answer 6

Packaged in the taste buds

Question 7

What are the taste buds

Answer 7

Organs of taste

Question 8

What do taste buds consist of

Answer 8

sensory receptor cells and support cells arranged like slices of orange

Question 9

What is the life span of a taste receptor cell

Answer 9

10 days

Question 10

What are the taste receptor cells replaced form

Answer 10

Basal cells within the taste buds

Question 11

What do taste receptor cells within taste buds synapse with

Answer 11

Afferent nerve fibres

Question 12

Where are taste buds located

Answer 12

tongue
palate
epiglottis
pharynx

Question 13

Where are the majority of taste buds

Answer 13

In the papillae of the tongue

Question 14

Describe the appearance of papillae

Answer 14

Finger like structures which give rise to the rough appearance of the dorm of the tongue
Seen as little red dots or raised bumps

Question 15

How many types of papillae do we have?

Name these

Answer 15

4
Filiform 
fungiform
vallate
foliate

Question 16

What type of papillae do not contain taste buds

Answer 16

Filiform

Question 17

What alters cell ionic channels to produce depolarising receptor potential

Answer 17

Binding of taste provoking chemical (tastant)

Question 18

The receptor potential initiates what

Answer 18

Aciton potentials in afferent nerve fibres which synapse with receptor cells

Question 19

How do afferent taste fibres reach the brainstem

Answer 19

Via 3 cranial nerves:
VII (chorda tympani branch of facial nerve) - anterior 2/3rds of the tongue
IXth - posterior third of the tongue
X - caranial (vagus) nerve - areas other than the tongue e.g. epiglottis and pharynx

Question 20

What are the 5 primary tastes

Answer 20

salty 
sour
sweet 
bitter
umani (meaty or savory)

Question 21

What stimulates salty taste

Answer 21

Sodium chloride (chemical salts)

Question 22

What stimulates sour taste

Answer 22

Acids which contain free hydrogen ions (H+)

Question 23

What stimulates sweet taste

Answer 23

configuration of glucose

Question 24

What stimulates unami taste

Answer 24

amino acids especially glutamate

Question 25

What is ageusia

Answer 25

loss of taste function

Question 26

What can cause aguesia

Answer 26

Nerve damage, local inflammation e.g. glossitis, radiation, tobacco, some endocrine disorders

Question 27

What is Hypogeusia

Answer 27

Reduced taste function

Question 28

What can cause Hypogeusia

Answer 28

Chemotherapy or medications

Question 29

What is Dysgeusia

Answer 29

Distortion of taste function

Question 30

What can cause Dysgeusia

Answer 30

``` Glossitis Gum infections tooth decay reflux URI medications neoplasms chemo zinc deficiency ```

Question 31

Where is olfactory mucosa found

Answer 31

In the ceiling of the nasal cavity

Question 32

What types of cells are found in olfactory mucosa

Answer 32

Olfactory receptor cells supporting cells basal cells

Question 33

What are olfactory receptors

Answer 33

Specialised endings of renewable afferent neurones

Question 34

Describe the appearance of each neuron

Answer 34

It has a thick short dendrite and an expanded end called an olfactory rod

Question 35

Where are cilia in relation to the olfactory rods

Answer 35

They project to the surface of the olfactory mucosa (10-12 cilia per olfactory receptor neuron)

Question 36

What bind to cilia

Answer 36

Odorants (molecules that can be smelled)

Question 37

What is the life span of olfactory receptors

Answer 37

About 2 months

Question 38

What do basal cells act as

Answer 38

precursors for new olfactory receptor cells

Question 39

What do axons of olfactory receptors collectively form

Answer 39

Afferent fibres of olfactory nerve

Question 40

Where do the olfactory receptors lie?

Answer 40

They pierce the cribriform plate of the ethmoid bone and enter the olfactory bulbs in the inferior surface of the brain

Question 41

What is the function of the olfactory bulbs

Answer 41

They transmit smell information to the brain

Question 42

What happens to odorants during quiet breathing

Answer 42

They only reach smell receptors by diffusion

Question 43

What does the act of sniffing do

Answer 43

enhances smelling by drawing air currents upwards within the nasal cavity

Question 44

In order to be smelled, what 2 things must a substance be

Answer 44

``` Sufficiently volatile (some of its molecules can enter the nose with inspired air) Sufficiently water soluble (can dissolve in the mucus coating of olfactory mucosa) ```

Question 45

How many odours can humans discriminate between and how

Answer 45

Thousands - olfactory receptors have different sensitivity to different substances

Question 46

What is anosmia

Answer 46

Inability to smell

Question 47

What can cause anosmia

Answer 47

Viral infections, allergy, nasal polyps, head injury

Question 48

What is hyposmia

Answer 48

reduced ability to smell

Question 49

What might hyposmia be an earl sign of

Answer 49

Parkinson's disease

Question 50

What is dysosmia

Answer 50

Altered sense of smell

Question 51

What are some examples of dysosmia

Answer 51

Differently interpreting some odours and hallucinations of smell