Anthony J Greene 2

Circumvilliate

Folliate

Filliform

Fungiform

Papillae Circumvilliate Folliate Filliform Fungiform

Anatomy of Taste

GUSTATORY SENSATION• It is a chemical sense and gives taste of food or not-food materials•Substance to be tasted should either be in a solution or diluted with saliva•Taste must be distinguished from flavor which includes olfactory, thermal and tactile attributes of food in addition to taste•Taste stimuli are detected by taste receptors-

1.Tongue 2.Mouth3.Pharynx

TASTE BUD•Sense organ for gustation is taste bud•Present on dorsum of tongue [ except filiform papillae ] , palate, epiglottis, and in pharynx and larynx to a extent•Flask shaped with receptor cells and supporting cells•Each receptor cells live for 10 days after which it is replaced by new cell from basal cells•Receptor cells have 6 to 18 hair like projections called microvilli which has the receptors on its membrane •The base of the receptor cells are in contact with afferent nerve endings•Anterior 2/3rd is supplied by facial nerve and the posterior 1/3rd by the glossopharyngeal nerve, the vagus nerve supplies the taste buds present in larynx

Anthony J Greene5

Taste Anatomy

PATHWAY•The primary sensory neurons are situated in the geniculate ganglion [ 7th nerve ] petrous ganglion [ 9th nerve] nodose ganglion [10th nerve]•The axons from these neurons enter into the medulla and end in the nucleus of tractus solitarius and second order neurons start here•Fibers from the NTS join the medial lemniscus and proceed upwards to ventral posteromedial nucleus of thalamus, where 3rd order neuron arise •The fibers go to cortical area for taste sensation in the somatosensory cortex

PATHWAY

STIMULI•Substances must dissolve in saliva before they can stimulate taste receptors•Four basic types of taste sensation

1. Sweet sensation Organics [ sugar, glycols, aldehyde] Tip of tongue

2. Bitter sensation Alkaloids [ quinine, caffeine ] harmful Back of tongue

3. Salty sensation Anions of ionizable salts [ NaCl, NaBr etc ] Front half of each side of tongue

4. Sour sensation Acids [ acetic acid, tartaric acid etc] Posterior half of each side of tongue

SOME FEATURE OF TASTE SENSATION

•Threshold concentration for taste sensation for different substances are different eg; for NaCl it is 2000mmol/L whereas for strychnine 1.6mmol/L•Taste sensation shows contrast, a sweet substance taste more sweet if taken after a bitter substance, this is called successive contrast. If salt is placed on one border of the tongue then sensitivity for sweet substance increases in the other border and is named as simultaneous contrast•Adaptation is another important feature, if sweets are taken before tea with the usual amount of sugar, then the tea tastes less sweet due to adaptation•After taste is an interesting phenomenon , if miraculin a plant protein is taken first and then any sour substance taken tastes sweet•Some abnormalities are

1. Ageusia = absence of taste sensation2. Hypogeusia = decreased taste sensation3. Dysgeusia = disturbed taste sensation

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