Chapter 4 Pns - Gustation

Front 1

Taste buds consist of

Back 1

1. taste pore: opening through which fluids in mouth come into contact with surface of receptor cells

2. taste receptor cells: modified epithelial cells with microvilli

Front 2

All tastes are varying combinations of what 5 primary tastes

Back 2

sweet, salty, bitter, sour, umami/savoury

Front 3

Salty tastes are stimulated by

Back 3

chemical salts especially NaCl

Front 4

Sour tastes are caused by

Back 4

acids which contain a free hydrogen ion, H+

Front 5

Sweet tastes are evoked by

Back 5

configuration of glucose

Front 6

Bitter tastes are stimulates by

Back 6

more chemically diverse group of testants (alkoids, toxic plant derivatives, poisonous substances)

Front 7

Process of gustation

Back 7

tongue/oral cavity -> taste buds -> taste receptors -> plasma membrane of taste receptors on microvilli -> binds w/ chemicals -> chem. binding alters ionic channels -> depolarization -> receptor cell synapses w/ afferent nerve fibres -> signals sent via synaptic input -> brainstem & thalamus -> hypothalamus and limbic sys (taste pleasant/unpleasant, behavioural responses) AND cortical gustatory (perception of taste & smell)

Front 8

Process of salty taste

Back 8

stimulated by NaCl -> direct entry of Na+ activates Na+ ion channels on receptors pl. mem. -> causes depol. -> salty taste perception in brain

Front 9

Process of sour taste

Back 9

citric acid in lemon -> yields acid & H+ ion -> H+ ion blocks K+ channels in receptors cell mem. -> results in decreases passive movement of K+ ions out of cell -> reduces internal negativity (more + charge inside) -> depol. (action pot) -> sour taste in brain

Front 10

Perception of sweet taste

Back 10

glucose configuration -> glucose binds with taste cell receptor -> binding activates G-Protein -> turn on cAMP -> results in phosphorylation and blockage of K+ channels -> depol (action pot) -> sweet taste perceived in brain

Front 11

Perception of bitter taste

Back 11

binds to receptor -> alters ion channels on receptors pl. mem. -> depol -> action pot -> different tastes

Front 12

G-protein in taste

Back 12

Gustducin considered as one of the bitter signaling pathways (which sets off a 2nd msngr pathways in the taste cell)

Front 13

Perception of Savoury (umami) taste

Back 13

AA glutamate in meat, glutamate binds to G-Protien -> activates a 2nd msngr pathways -> depol -> action pot -> perception of savoury taste

Front 14

cAMP is

Back 14

a second messenger pathway in taste cell

Front 15

By 4th month baby prefers __________ to __________ and taste begins to by influenced by experience

Back 15

prefers salt water over plain water

Front 16

What happens to taste buds with aging?

Back 16

there is a decline in the number of taste buds

- sweet taste remains by sour, salty and bitter decline