Physiology of Taste and Smell Flashcards

1
Q

how do taste and smell influence foot intake

A

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

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2
Q

what are the organs of taste

A

taste buds (contain sensory receptor cells)

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3
Q

what makes up taste buds

A

sensory receptor cells and support cells

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4
Q

what is the lifecycle of taste receptor cells

A

last about ten days

are replaced from basal cells within the taste buds

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5
Q

where are taste buds

A

tongue, palate, epiglottis and pharynx

majority in the papillae in the tongue

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6
Q

what do taste receptor cells synapse with

A

afferent nerve fibres

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7
Q

what are papillae

A

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

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8
Q

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

A
filliform (most numerous do not contain taste buds)
fungiform 
vallate 
foliate 
(last three all contain taste buds)
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9
Q

describe how taste produces responses in the brain

A

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

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10
Q

in taste what is the role of CN VII

A

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

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11
Q

in taste what is the role of CN IX

A

supplies the posterior 1/3rd of the tongue

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12
Q

in taste what is the role of CN X

A

supples areas other than the tongue (epiglottis, pharynx)

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13
Q

what are the five primary tastes

A

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

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14
Q

what stimulates salty tastes

A

chemical salts -esp sodium chloride

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15
Q

what stimulates sour tastes

A

acids which contain free hydrogen ions

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16
Q

what stimulates sweet tastes

A

configuration of glucose

17
Q

what stimulates bitter tastes

A

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

18
Q

what stimulates umami tastes

A

triggered by amino acids (esp glutamate)

19
Q

what is ageusia

A

loss of taste function (can be temporary or permanent)

20
Q

what can cause ageusia

A

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

21
Q

what is hypogeusia

A

reduced taste function

22
Q

what can cause hypogeusia

A

chemotherapy, medications

23
Q

what is dysgeusia

A

distortion of taste function

24
Q

what can cause dysgeusia

A

many causes inc:

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

25
Q

where is the olfactory mucosa

A

in the ceiling of the nasal cavity (dorsal roof)

26
Q

what are the three types of cells in the olfactory mucosa

A

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

27
Q

what are olfactory receptors

A

specialised endings of renewable afferent neurones

each has thick short dendrite and an expanded end called an olfactory rod

28
Q

what do the olfactory rods do

A

cilia project from these

29
Q

what are odorants

A

molecules that bond to the cilia on the olfactory rods

30
Q

what is the life cycle of olfactory receptors

A

lifespan of 2 months

basal cells act as precursors for new olfactory receptor cells

31
Q

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

A

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

32
Q

can you smell during quiet breathing

A

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

33
Q

why does sniffing enhance smelling

A

draws air currents upwards towards the olfactory mucosa

34
Q

what must a substance be in order to be smelt

A
sufficiently volatile (molecules can enter nose with inspired air) 
sufficiently water soluble (can dissolve in the mucous coating the olfactory mucosa
35
Q

what is anosmia

A

inability to smell (can be temporary or permanent)

36
Q

what can cause anosmia

A

viral infections, allergy, nasal polyps, head injury

37
Q

what is hyposmia

A

reduced ability to smell

38
Q

what can cause hyposmia

A

similar causes to anosmia

can also be early sign of parkinsons

39
Q

what is dysosmia

A

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