Taste And Olfaction Flashcards
How is olfaction sensed ?
By chemoreceptors
Sensation form air borne odourants/volatiles
How is taste sensed ?
By chemoreceptors
Sensation from hydrophilic substances dissolving in saliva
What behaviours do taste and smell play a role in ?
Feeding Parenting Mating Altering Territorial behaviour
What is the dominant sense in humans ?
Vision
What is hypogeusia and ageusia ?
Hypogeusia= reduced ability to taste Ageusia = inability to taste
What is hyposmia and anosmia ?
Hyposmia= reduced ability to smell or detect odours Anosmia= inability to detect odours
What are the detection threshold holds for salt, sugar, acids and alkaloids ?
Salt - 10mM
Sugar- 20mM
Acids- 0.01mM
Alkaloids - 0.0001mM
What are the 5 basic tastes ?
Sweet Bitter Sour Salty Savoury - umami
Why is spicy or minty not classified as a taste ?
Because they are not detected by taste receptors, they are classed as somatosensory responses
Other than taste what other factors contribute to taste sensation ?
Visual aspect of food, smell of food and also texture of food
What are the 3 different papillae ?
Circumvallate, foliate and fungiform
Describe circumvallate papillae
Largest- many thousands
Located at the posterior of the tongue
Describe foliate papillae
Contain many hundreds of taste buds
Elongated structure along the lateral posterior edge of tongue
Describe fungiform papillae
Smallest contain 1 to 2 taste buds
Widespread across anterior surface of the tongue
What are taste buds like ?
Garlic clove shaped - 30 micrometers
Contain about 50-60 cells
Have microvilli to project into taste pore
Lifespan of about 2 weeks - replenished by basal cells
How do tastants trigger a transduction cascade ?
Direct pass through ion channels - salty and sour because you have cations which can pass through
Bind to and block ion channels
Bind to be open ion channels
Bind to receptors and activate a 2nd messenger system to modulate ion channels
Why are taste buds not true neurons ?
Because they not have an axon
Why is the highest sensitivity on the tongue for bitter tastes ?
Posterior
Where is there higher sensitivity for sweet taste on the tongue ?
Tip of the tongue
Describe the sensory transduction of taste receptor cell
Dissolved molecules bind to sites or ion channel modulation in apical microvilli
Trigger membrane depolarisation and increase AP firing
Accompanied by increas I’m intracellular calcium which cause nt release
Released onto afferent nerves 7,9,10
Where do nerves 7, 9 and 10 receive their innervation from ?
7- anterior 2/3 of tongue
9- posterior 1/3 of tongue
10- epiglottis
What is the transduction cascade for salty tastants ?
Salty food increases sodium concentration which passes down concentration gradient through amiloride sensitive sodium channels
This depolarises the cell causing calcium influx and therefore nt release
What is the transduction cascade for sour tastants ??
Sourness is a reflection of acidity
He increased proton concentration passes through amiloride sensitive sodium channels causing depolarisation and they also block potassium channels helping to contribute to depolarisation
What is the transduction cascade for bitter tastants ?
Bind to specific T2R gpcr
Increases PLC
Increases IP3
IP3 triggers opening of TRPM5 channels allowing calcium inflict and therefore nt release
Also activates sodium channels causing calcium release from intracellular stores
