1. Taste/Gustatory anatomy:
Tongue map: different section of the tongue responsible for different taste. This is
Wrong! Instead, we have receptors for all different tastes located all over our
1) Fungiform Papillae (cluster of taste buds.
Three main types): mainly margins and tip of tongue,
mushroom shaped (2 ), contain only one bud??or six?
2) Foliate Papillae: back sides of the tongue, look
like a series of folds, each contains many different
3) Circumvallate Papillae: flat hills with circular
trench, back of the tongue, each contain many
different buds (3 )
4) Filiform Papillae: No taste function, front of
tongue (1 ), contain only one bud??
Taste Buds 味蕾 : a group of different cells; each bud contains 50 -150 cells; taste
bud cells made up of active taste cells, basal cells, and other cells
1) Basal Cells: young taste cells that haven’t matured
(the small round cells at the bottom)
2) Taste Receptor Cells: modified skin cells; just like skin
cells, they have a limited life span-- individual taste cell will
last just a few days. When they die they got replaced by basil
cells that got matured.
3) Other cells: responsive to other stimuli besides
chemical stimuli, that contribute to our sensation taste, such
as temperature, pressure, and pain.
4) Microvilli: projections from the receptor cell that will
open up into the surface of the tongue and get exposed to
the saliva; they are extensions of the cell membrane. 2. Physiology of the Gustatory System:
How Taste Cells Transduce Taste into Neural Signal:
Transduction: generic cell-- there’s microvilli, nucleus, but it’s not a
neuron, so no action potentials, but will release neurotransmitters to an
afferent nerve, and the release will be provoked by an influx of calcium;
5 pure tastes: defined by the 5 tastes receptors; the input source must be
water soluble or else we won’t taste it
Through Ion Channels (no receptor taken place):
1) Salt: something salty is broke down into Na+ and make it way into the
sodium (Na+) channels at the microvilli of a taste receptor cell, and into
our taste cell depolarization of our taste cell (when efficiently
depolarized) opening of calcium (Ca2+) channelsCa2+ influx
neurotransmitter release increase firing in the afferent nerve who
carry the signal to the brain
2) Sour: sour substance broke down into hydrogen atoms (H+), taking in
through the ion channelH+ goes in, K+(Potassium) goes out
depolarization …(same as above)
True Chemical receptor, lock-and-key mechanism: Receptors either is coupled to an ion channel itself or to G-protein
(second messenger): activating the channel that is coupled to G-protein
will lead metabolic changes in the cell. Those metabolic changes are then
going to affect depolarization.
3) Sweet: sugar molecule comes in binds to some sweet receptorthe
G-protein that’s binding with it got modified (temporally uncouple)the
increase in cAMP production in the cell by-product: negatively charged
ion in the cell to leave depolarize the cell…(same as above)
4) Umami: both types receptors—(1) receptor coupled directly with Na+
or Ca2+ channels, as a key, open the channel, ….(same as above), (2)
Umami molecule comes in and binds to receptor, cause the G-protein
uncoupled temporally decrease in cAMP production through a
series event (unknown) depolarization…(same as above)
5) Bitter: Two types of G-protein couple that leads to a chain of events 1)
same as umami’s 2) don’t need to worry about the IP3 thing.
How to Code Stimulus:
Chorda Tympani: part of
one of three cranial nerves that
are involved in taste.
In 12 different individual
fibers for a rat, we look at how