Taste and Smell Flashcards
pheromones
is a chemical signal released by 1 member of the species and sensed by another species to trigger an innate response.
A specialized part of olfactory epithelium in animals called the a accessory olfactory epithelium does what?
the accessory olfactory epithelium. It sends projections to the accessory olfactory bulb which then sends signals to the brain.
Within the accessory olfactory epithelium, you have a structure called the vomeronasal system.. what do they do
In vomeronasal system, there are basal cells and apical cells. They have receptors at tips.
Molecule will come in and activate receptor on basal cell/apical cell here. Basal cell send signal down what pathway?
sends axon through accessory olfactory bulb to glomerulus, then mitral or tufted cell which eventually goes to the amygdala (part of the brain)
Amygdala is involved with
Amygdala is involved with emotion, aggression, mating etc. In temporal lobe, also involved in memory/decision making, emotional reactions
Signal transduction is where
Signal transduction is where the signal binds to the receptor, which binds to GPCR. Depolarization. The signal goes to the brain.
In humans have vomeronasal organ, but no accessory olfactory bulb which means
we rely very little on pheromones.
If your smell is knocked out/closed, you can’t
taste things as well.
Smell is also known as
lfaction
Area in nostril called the
olfactory epithelium (olfactory sensory cells)
Separating the
olfactory epithelium from the brain is the
cribriform plate (bone with little holes that allow olfactory sensory to send projections to the brain).
Above the cribriform plate is
an extension from the brain – olfactory bulb
olfactory bulb is a
a bundle of nerves that sends little projections through the cribriform plate into the olfactory epithelium, which branch off
All cells sensitive to benzene will fire to one olfactory bulb – called a
glomerulus – designation point for various sensory olfactory cells that are sensitive to the same molecule. For example, a benzene glomerulus.
At the glomerulus, the receptors
then synapse on another cell known as a mitral/tufted cell that project to the brain. This organization is there because it’s easier for one cell to send a projection to the brain instead of thousands.
How does a molecule bind to a receptor and cause an AP?
The molecule binds to the GPCR receptor on odor molecule -> GPCR on olfactory epithelia->G-protein dissociates and causes a cascade of events inside the cell->G protein binds to ion channel which allows cells outside the cell to come inside->opens and triggers an AP->goes to cribriform plate->glomerulus->activate mitral/tufted cellàsynapse to brain.
100 of different olfactory epithelial each sensitive to one particular molecule. They all send projections to one glomerulus respective to their specialization. Then they synapse onto a mitral/tufted cell which signals to the brain.
Just the main idea no question or term just understand
what doesn’t synapse on to thalamus
Smell (olfaction) and taste (gustation) doesn’t synapse onto the thalamus
Smell (olfaction) and taste (gustation) are ipsilateral or contralateral.
ipsilateral
vision/hearing/touch are ipsilateral or contralateral.
contralateral.
The labeled-line theory of olfaction describes
a scenario where each receptor would respond to specific stimuli and is directly linked to the brain.
The vibrational theory of olfaction
asserts that the vibrational frequency of a molecule
gives that molecule its specific odor profile
Steric theory of olfaction, or shape theory
asserts that odors fit into receptors similar
to a lock-and-key.
anosmia
inability to perceive order
The pathway for olfaction goes from
the olfactory bulb to the amygdala and the piriform
cortex. From there the signal is transmitted to the orbitofrontal cortex.
We have 5 main tastes
bitter, salty, sweet, sour, and umami (ability to taste glutamate).
Taste buds, in turn,
are contained in structures
papillae
anterior taste buds
are mushroom-shaped structures located on the tip and sides of the tongue, which contain taste buds. aka fungiform
side taste buds
aka Foliate papillae are folded structures at the back of the tongue on both sides, which contain taste buds
back taste buds
AKA Circumvallate papillae are flat mound structures that are found at the back of the tongue and contain taste buds.
Filiform papillae do not contain
Filiform papillae do not contain taste buds and exist all over the tongue. The center of the tongue contains only filiform papillae. This is why stimulation of the center of the tongue does not cause a taste sensation, while the back and perimeter produce a broad range of taste sensations.
Tastant
a substance that stimulates the sense of taste
Gustducin
a protein associated with the sensation of taste
Front 2/3rd tongue carries signals via
7th cranial nerve via the chorda tympani
Posterior (Rear 1/3rd ) tongue carries signals
via the 9th and 10th cranial nerves
(glossopharyngeal and vagus)
Labelled lines model
Each taste bud receptor has 5 axons, all which send separate taste information to different parts of the gustatory (taste) cortex. Remain separate to the brain. And they all synapse on diff parts of the gustatory (taste) cortex.
Sweet, umami, and bitter cells rely on
GPCR receptors.
Sour and salty rely on
ion channels.
how do GPCR receptors pathway work for taste
Glucose binds GPCR, conformational change, G-protein dissociates, opens ion channels, cause cell to depolarize and fire an AP
how do ion channels pathway work for taste
o Salty tastants bind to salt receptors which detect the presence of sodium ions and should not be chosen by the researchers.
o Sour tastants bind to sourness receptors that react with hydrogen cations (H+). Once H+ binds to the receptor, it closes the potassium channels.
What happens if we put salty receptor inside a sweet cell?
Receptors in membrane bind to glucose. But let’s insert a salty receptor. Since axon from cell leads to brain, if NaCl comes in, it activates the receptor, + ions go inside, sweet cell depolarizes and fires AP, and brain interprets it as a sweet signal. Put a salty receptor in a sweet cell, can trick your brain into thinking salt is sugar!
