Physiology of Taste (Gustation) Flashcards
What do taste buds consist of?
sensory receptor cells
support cells
arranged like orange segments
How long is the lifespan of a taste receptor cell?
10 days
Where are taste receptor cells replaced from?
basal cells within the taste buds
What do taste receptor cells synapse with?
taste afferent nerve fibres
Where are taste buds present?
tongue
palate
epiglottis
pharynx
Where are the majority of taste buds located?
papillae
What are papillae?
finger-like structures which give rise to the rough appearance of the dorsum of the tongue
What papillae is the most numerous?
filiform
What papillae contains no taste buds?
filiform
Which papillae contain taste buds?
fungiform
vallate
foliate
What is the mechanism of taste?
1 - binding of tastant to receptor cells causes depolarising receptor potential
2 - receptor potential initiates AP in afferent nerve fibres which synapse with receptor cells
3 - signals conveyed by cranial nerves via brainstem and thalamus to cortical gustatory areas
What CN supplies the anterior 2/3rds of the tongue?
CN VII - chordae tympani branch of the facial nerve
What CN supplies the posterior 1/3rd of the tongue?
CN IX - glossopharyngeal
What CN supplies areas other than the tongue?
CN X - vagus
What are the five primary tastes?
salty sour sweet bitter umani (meaty or savoury)
What stimulates a salty taste?
chemical salts
especially sodium chloride
What stimulates a sour taste?
acids which contain free hydrogen ions
What stimulates a sweet taste?
glucose
What stimulates a bitter taste?
diverse group of tastants - e.g. alkaloids, poisonous substances, toxic plant derivatives
What is a tastant?
taste provoking chemical
What stimulates an umami taste?
amino acids
especially glutamate
What is ageusia?
loss of taste
Give examples of things that can cause ageusia
nerve damage
local inflammation - glossitis, radiation, tobacco etc
some endocrine disorders
What is hypogeusia?
reduced taste
Give examples of things that can cause hypogeusia
chemotherapy
medication
What is dysgeusia?
distortion of taste
Give examples of things that can cause dysgeusia
glossitis gum infections tooth decay reflux upper respiratory tract infections medications neoplasms chemotherapy zinc deficiency
