Physiology and histology of taste

organisation of the papillae and cells

tongue → gustatory papillae → taste bud → taste cell

epithelium of papillae

stratified squamous

where are taste buds

lateral edges of papillae

where do molecules enter the taste bud

taste pore

3 types of mechanical papillae

filiform

conical

marginal

3 types of gustatory papillae

fungiform - mushroom in rostral 2/3

vallate - deep groove and circular between body and base

foliate - between body and base at edges in horse and pig

5 types of taste substance

sweet - carbohydrates or aritificial sweetners

salty - ions present like Na+ and K+

umami - amino acids

sour - H+ ions

bitter - toxins

4 types of taste cell

Type I - supporting cell to mop up excess neurotransmitters like ATP

Type II - receptor cell for sweet, umami and bitter tastes

Type III - presynaptic cell for sour tastes

Type IV - cell renewal

chicken taste preference

no preference

what sort of receptor is the type II

GPCR using phospholipase C - PIP2 to IP3

give the process for the type III presynaptic cells for activation

the salt crosses the cell membrane and converts back to H+ ions which closes K+ ion channels

this depolarises the cell and causes calcium ion channels to open and calcium ions to move into the cell which causes vesicles containing serotonin to be released to the outside of the membrane

what is going on with GABA and glutamate

GABA is released by type III to inhibit type II through paracrine means

nerve endings secrete glutamate which has an excitatory effect on presynaptic cells III

what happens in the medulla oblongata

unconscious like triggering the release of digestive juices and salivary gland

what happens int he gustatory cortex

CONSCIOUS PERCEPTION

how does taste link to smell

swallowing and deglutition leads to retronasal airflow causing the particles to reach the ethmoidal conchae and be perceived from there