Physiology of Taste and Smell Flashcards
what type of receptors are taste and smell receptors
chemoreceptors - stimulated by binding to particular chemicals
stimulation induces a pleasurable/objectionable sensation
what protectional function does taste and smell have
check for quality control eg poisons taste bitter, off food tastes bad
do taste and smell influence eachother ?
yes, taste perception is influenced by information from smell receptors
do taste and smell have an influence on the flow of digestive juices?
yes
gustation
the action of tasting
where are the sensory receptor cells of taste found
mainly taste buds - they are the sense organs of taste
what is the life span of taste receptor cells
about ten days, they are replaced from basal cells in the taste buds
sensation of taste and taste buds
taste buds consist of sensory receptor cells and support cells
the receptor cells synapse with afferent nerve fibres
where are taste buds mainly present
tongue, palate, epiglottis and pharynx
what gives the rough apperance to the dorsum of the tongue
papillae - contain taste buds
which papillae on the tongue are not involved in tasting
filliform - the most numberous, they are involved in general sensory eg touch and temperature
tastant
capable of eliciting gustatory excitation e.g. stimulating the sensation of taste
describe the stimulation of the sensation of taste
binding of tastant to receptor cell alters cell ionic channels and produces depoalrising receptor potential
RP initiates action potential in afferent nerve fibres which synapse with receptor cells
signals conveyed by CN via brainstem and thalamus to cortical gustatory areas
which cranial nerves do afferent taste fibres reach the brainstem via
CNVII
CNIX
CNX - areas other than tongue
what are the 5 primary tastes
salt
sour
sweet
bitter
umami (meaty or savoury)
salty taste
stimualted by chemical salts, especially NaCl
sour taste
stimulated by acids which contain free hydrogen ions
sweet taste
stimulated by configuration of glucose
bitter taste
stimulated by diverse group of tastants eg alkaloids, poisonous substances and toxic plant derivatives
umami taste
triggered by amino acids, especially glutamate
ageusia
loss of taste sensation
can be caused by eg nerve damage, local inflammation, endocrine disorders
what is ageusia often associated with
anosmia
hypogeusia
reduced taste function
can be caused by eg chemo and medications
dysguesia
distortion of taste function
can be caused by e.g. glossitis; gum infections; tooth decay; reflux; upper respiratory infections; medications; neoplasms; chemotherapy; zinc deficiency
where is the olfactory mucosa located
3.
ceiling of nasal cavity
what is the function of the basal cells in the olfactory mucosa
secrete mucous
which 3 types of cells does the olfactory mucosa contain
basal cells
supporting cells
olfactory receptor cells
describe the olfactory receptor cells
specialised endings of renewable afferent neurones
each neuron has a thick short dendrite and an expanded end known as an olfactory rod
cilia project from the olfactory rod onto the surface of the olfactory mucosa (mucus layer)
odorants bind to the cilia
what is the lifetime of olfactory receptors
2 months
- basal cells act as precursors for new olfactory receptor cells
how are different odours discriminated between
olfactory receptors have different sensitivity to different substances
what is the purpose of sniffing (olfaction)
during quiet breathing odourants only reach smell receptors by diffusion as the olfactory mucosa is above the normal path of airflow
sniffing enhances smelling by drawing air upwards within the nasal cavity
what 2 things must a substance be to be smelled
sufficiently volatile to enter the nose in inspired air
sufficiently water soluble to dissolve in the mucus coating the oflactory mucosa
what may be an early sign fo Parkinsons disease
hyposmia
causes of anosmia
viral infections, allergy , nasal polyps, head injurt
examples of dysosmia
differently interpreting some odours and hallucinations of smell
