Chemical Senses Flashcards
What is flavour?
A combination of smell and taste
Can include texture and other sensory aspects
What is difficult to identify without olfaction?
Foods
How did our gustation adapt?
To test whether food was edible, spoiled, or poisonous
What do salty foods maintain?
Electrolyte balance
What do sour foods do?
Detect vitamins and acids that cold burn tissue
What does sweet food ensure?
Energy reserves and fuel for neurons
What is the purpose of bitter tastes?
To avoid toxins/poisons
What are the qualities of salty stimuli?
in-/organic salts
Cation is the most important
What are the qualities of sour stimuli?
in/organic acids that release H+ ion in solution
What are the qualities of sweet stimuli?
Complex organic molecules: sugar, aspartame
What are the qualities of bitter stimuli?
Varied
Alkaloids
Some nitrogen-containing molecules
What are the qualities of umami stimuli?
Savory
Salts of glutamic acid
Where are salts of glutamic acid found?
Protein-rich foods
Was isolated from seaweed
What is MSG?
Glutamic acid + Na+
There are G protein-coupled receptors for MSG
What are the bumps on the tongue called?
Papillae
Where are taste buds found?
The fungiform = on tip and sides
Foliate = folds along sides of tongue
Circumvallate = flat mounds surrounded by a trench on the back of the tongue
Soft palate
What projects out of the taste pore?
Microvilli.
How does the transduction of taste work?
Sodium penetrates membrane of the receptor = depolarization
Sour substances contain H+ which blocks ion channels
Other substances form bonds with molecules in the membrane causing chemical changes within the cell
What is label-line sensory coding?
Different taste stimuli activate specific fibers
The firing rate represents the intensity
Activity in a few fibre types is all that is needed to code stimuli
What is the problem with label-line sensory coding?
Many substances elicit more than one taste
What is cross-fibre patterning?
There are no specialized receptors for each taste
Taste quality signaled by the pattern of activity in many fibers
Each fiber responds to a variety of substances, but is tuned to respond best to one type of taste
What nerve is made up from nerve fibers from the front and sides of the tongue?
The chorda tympani nerve
What nerve is made up from fibers from the back of the tongue?
The glossopharyngeal nerve
What nerve is made up from fibers from the mouth and throat?
The vagus nerve
What nerve is made up of fibers from the soft palate?
The superficial petrosal nerve
Where do all of the nerves connect to?
The nucleus of the solitary tract in the medulla
What are the pathways in the medulla?
Thalamus => gustatory cortexes in the frontal lobe
Frontal operculum cortex and anterial insula (conscious taste perception) -> orbitofrontal cortex (emotion and reward)