Physiology of Taste and Smell Flashcards
what are chemoreceptors
receptors for taste and smell which are simulated by binding with particular chemicals
what does the stimulation of taste and smell receptors produce
a good or bad sensation - functions as a checkpoint for quality control eg. most poisons taste bitter, off foods taste bad/sour
where are the sensory receptors of taste found
packages into taste buds
what is the life span of taste buds
10 days - then replaced with basal cells within the taste but
how to taste buds send signals to the brain
via afferent neurons which synapse at the bottom of the taste bud
where do the majority of taste buds sit
the papillae of the tongue (finger like structures which give rise to the rough appearance of the back of the tongue)
What are the 4 types of papillae found in the human tongue
filiform
fungiform
vallate
foliate
which type of papillae does not contain taste buds
filiform (also most abundant)
how do taste buds work
- taste provoking chemicals cause depolarisation of receptor cells
- receptor cell potential initiates action potential in afferent nerve fibres
- signals are conveyed to the brain stem to the thalamus and cortical gustatory areas
what nerves take afferent nerve fibres from the taste buds to the brain stem
CNVII (chordates tympanic branch of the facia nerve - anterior 2/3 of the tongue)
CNIC (glossopharyngeal nerve for posterior 1/3 of the tongue)
CNX for taste buds around the tongue on the epiglottis and pharynx
what are the 5 primary tastes
salty sour sweet bitter umani (meat/savoury)
what stimulates a salty tase
chemical salts - especially sodium chloride
what stimulates a sweet taste
configuration of glucose
what stimulates a sour taste
acids which contain free hydrogen ions
what stimulates a bitter taste
diverse group including alkaloids, poisonous substances and toxic plant derivatives
what is ageusia
a loss of taste function
causes of ageusia
nerve damage local inflammation (glossitis, radiation, tobacco) some endocrine disorders
what is hypogeusia
reduced taste function
what can cause hypotenusia
medication
chemotherapy
what is dysgeusia
distortion of taste function
what can cause dysgeusia
glossitis gum infections tooth decay reflux upper resp infections medications neoplasms chemo zinc deficiency
what 3 cell types are contained in the olfactory mucosa
olfactory receptor cells
supporting cells
basal cells
what are olfactory receptor cells
specialised endings of renewable afferent neurons - each one has a short thick dendrite called an olfactory rod
what projects out of the olfactory rod
cilia (10-12 cilia per olfactory receptor neurone)
