Physiology of Taste and Smell

Question 1

how do taste and smell influence foot intake

Answer 1

induces a pleasurable or objectionable sensation
checkpoint for quality control
influences flow of digestive juices

Question 2

what are the organs of taste

Answer 2

taste buds (contain sensory receptor cells)

Question 3

what makes up taste buds

Answer 3

sensory receptor cells and support cells

Question 4

what is the lifecycle of taste receptor cells

Answer 4

last about ten days

are replaced from basal cells within the taste buds

Question 5

where are taste buds

Answer 5

tongue, palate, epiglottis and pharynx

majority in the papillae in the tongue

Question 6

what do taste receptor cells synapse with

Answer 6

afferent nerve fibres

Question 7

what are papillae

Answer 7

finger like structures, give rough appearance to the dorsum of the tongue

Question 8

what are the four types of papillae- which ones contain taste buds

Answer 8

filliform (most numerous do not contain taste buds)
fungiform 
vallate 
foliate 
(last three all contain taste buds)

Question 9

describe how taste produces responses in the brain

Answer 9

tastant (taste provking chemicals) bind to receptor cells altering the cells ionic channels- produces depolarising receptor potential

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

signals conveyed by cranial nerves (CNII, IX, X) via brainstem and thalamus to the cortical gustatory areas

Question 10

in taste what is the role of CN VII

Answer 10

chorda tympani branch supplies the anterior 2/3rd of the tongue

Question 11

in taste what is the role of CN IX

Answer 11

supplies the posterior 1/3rd of the tongue

Question 12

in taste what is the role of CN X

Answer 12

supples areas other than the tongue (epiglottis, pharynx)

Question 13

what are the five primary tastes

Answer 13

salty, sour, sweet, bitter, umami (meaty or savory)

Question 14

what stimulates salty tastes

Answer 14

chemical salts -esp sodium chloride

Question 15

what stimulates sour tastes

Answer 15

acids which contain free hydrogen ions

Question 16

what stimulates sweet tastes

Answer 16

configuration of glucose

Question 17

what stimulates bitter tastes

Answer 17

diverse tastants- inc: alkaloids, poisonous substances, toxic plant derivatives

Question 18

what stimulates umami tastes

Answer 18

triggered by amino acids (esp glutamate)

Question 19

what is ageusia

Answer 19

loss of taste function (can be temporary or permanent)

Question 20

what can cause ageusia

Answer 20

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

Question 21

what is hypogeusia

Answer 21

reduced taste function

Question 22

what can cause hypogeusia

Answer 22

chemotherapy, medications

Question 23

what is dysgeusia

Answer 23

distortion of taste function

Question 24

what can cause dysgeusia

Answer 24

many causes inc:

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

Question 25

where is the olfactory mucosa

Answer 25

in the ceiling of the nasal cavity (dorsal roof)

Question 26

what are the three types of cells in the olfactory mucosa

Answer 26

olfactory receptor cells, supporting cells, basal cells (secrete mucous)

Question 27

what are olfactory receptors

Answer 27

specialised endings of renewable afferent neurones each has thick short dendrite and an expanded end called an olfactory rod

Question 28

what do the olfactory rods do

Answer 28

cilia project from these

Question 29

what are odorants

Answer 29

molecules that bond to the cilia on the olfactory rods

Question 30

what is the life cycle of olfactory receptors

Answer 30

lifespan of 2 months | basal cells act as precursors for new olfactory receptor cells

Question 31

describe the formation and path of the olfactory nerve to the brain

Answer 31

axons of the olfactory receptors collectively form the afferent fibres of the olfactory nerve these pierce the cribriform plate of the ethmoid bone and enter the olfactory bulbs in the inferior surface of the brain from the bulbs neurones pass along the olfactory tract to reach the temporal lobes and olfactory areas

Question 32

can you smell during quiet breathing

Answer 32

odorants only reach smell receptors by diffusion (olfactory mucosa is above the normal path of airflow)

Question 33

why does sniffing enhance smelling

Answer 33

draws air currents upwards towards the olfactory mucosa

Question 34

what must a substance be in order to be smelt

Answer 34

``` sufficiently volatile (molecules can enter nose with inspired air) sufficiently water soluble (can dissolve in the mucous coating the olfactory mucosa ```

Question 35

what is anosmia

Answer 35

inability to smell (can be temporary or permanent)

Question 36

what can cause anosmia

Answer 36

viral infections, allergy, nasal polyps, head injury

Question 37

what is hyposmia

Answer 37

reduced ability to smell

Question 38

what can cause hyposmia

Answer 38

similar causes to anosmia | can also be early sign of parkinsons

Question 39

what is dysosmia

Answer 39

altered sense of smell (interpreting some odours and hallucinations of smell)