physiology-smell and taste

Question 1

how are chemoreceptors stimulated?

Answer 1

by binding to certain chemicals

Question 2

what allows taste and smell?

Answer 2

• taste receptors

- chemoreceptors

Question 3

how are the sensory receptors in the taste bus organised?

Answer 3

packaged close together

Question 4

what do taste buds consist of?

Answer 4

sensory receptor cells and support cells arranged like orange slices

Question 5

how long is the life span of a taste receptor cell nd how are they replaced?

Answer 5

about 10 days

-replaced from the basal cells within the taste buds

Question 6

what do taste receptor cells synapse with?

Answer 6

afferent nerve fibres

Question 7

where do taste buds present?

Answer 7

-mainly in tongue, palate, epiglottis and pharynx

Question 8

where on the tongue do most taste buds sit?

Answer 8

on papillae

Question 9

what are papillae?

Answer 9

• finger like structures which give rise to the rough appearance of the dorsum of the tongue
• can be seen on the tongue as little red dots or raised bumps

Question 10

what are the 4 types of papillae seen on the human tongue?

Answer 10

• filliform (most numerous and only one to not contain taste buds)
• fungiform
• vallate
• foliate

Question 11

what is the most numerous type of papillae?

Answer 11

filliform

Question 12

which papillae contain taste buds?

Answer 12

• fungiform
• vallate
• foliate

Question 13

which papillae does not contain taste buds?

Answer 13

filliform

Question 14

how do you taste?

Answer 14

• binding of taste provoking chemical (tastant) to receptor cells produces depolarising receptor potential
• receptor potential intiates action potentials in afferent nerve fibres which synapse with receptor cells
• signals conveyed by cranial nerves via brainstem and thalamus to cortical gustatory areas

Question 15

how do afferent taste fibres reach the brainstem?

Answer 15

via:
CNVII (chorda tympany branch of facial nerve) for anterior 2/3 of tongue
CNIX (glossopharyngeal nerve) for posterior 1/3 of tongue
CNX (vagus) for areas other than tongue e.g. epiglottis and pharynx

Question 16

what stimulates bitter tastes?

Answer 16

diverse group of tastants e.g. alkaloids, poisonous substance and toxic plant derivatives

Question 17

what stimulates sour tastes?

Answer 17

acids which contain free hydrogen ions (h+)

Question 18

what stimulates salty tastes?

Answer 18

chemical salts especially sodium chloride (NaCl)

Question 19

what stimulates sweet tastes?

Answer 19

the configuration of glucose

Question 20

what stimulates unami (meaty or savory) tastes?

Answer 20

amino acids especially glutamate

Question 21

what is ageusia?

Answer 21

loss of taste function

Question 22

what can cause ageusia?

Answer 22

• nerve damage
• local inflammation
• some endocrine disorders

Question 23

what is hypogeusia?

Answer 23

reduced taste function

Question 24

what can cause hypogeusia?

Answer 24

chemotherapy or radiotherapy

Question 25

what is dysgeusia?

Answer 25

distortion of taste function

Question 26

what may cause dysgeusia?

Answer 26

- glossitis - gum infections - tooth decay - reflux - URI - meds - neoplasms - chemo - zinc edficiency

Question 27

what are the 4 neural systems within the left and right sides of the nose?

Answer 27

- main olfactory system (cranial nerve I) - trigeminal somatosensory system (cranial nerve V) - the accessory olfactory system - the nerve terminalis

Question 28

what neural system mediates the common odours (rose, vanilla, chocolate)?

Answer 28

olfactory nerve (CNI)

Question 29

what neural system mediates chemical and non chemical stimulus and why is it important?

Answer 29

CNV (trigeminal nerve) - can detect irritation, burning, cooling ect - can make you cough in response

Question 30

what is important in the production of flavour from swallowed foods adding smell to taste and touch?

Answer 30

olfactory epithelium which exists in a small region of nasal epithelium

Question 31

what is needed for a substance to be smelled?

Answer 31

- sufficiently volatile (enter nose in aerosol form) | - sufficiently water soluble to dissolve in mucus coating of olfactory mucosa

Question 32

what must the odourant do before neural conduction can occur from the olfactory cleft to the brain?

Answer 32

- enter nose during active (sniffing) or passive (diffusion) process - pass to the olfactory cleft - move from the air phase to the aqueous phase

Question 33

why is mucus important in smell?

Answer 33

- moist and protective environment - aids in dispersing odourants to the olfactory receptors - from the mucus odourants either diffuse or are transported by specialised proteins to the receptors

Question 34

describe the olfactory neuroepithelium

Answer 34

pseudostratified columnar epithelium

Question 35

what cells does the olfactory neuroepithelium contain?

Answer 35

- bi polar sensory neurone (CNS in origin) extends odourant receptor containing cilia into the mucus - supporting cells (insulates and protects) - duct cell of bowmans glands secretes mucus - basal cells (stem cells)

Question 36

what is phantosmia?

Answer 36

smell perceived in the absence of stimulus