chapter 16 Flashcards
what are the five basic taste qualities
salty
sour
sweet
bitter
umami
what three components are involved in the chemical senses
taste:
- occurs when molecules enter the mouth in solid or liquid form and stimulate receptors on the tongue
olfaction:
- occurs when air borne molecules enter the nose and stimulate receptor neurons in the olfactory mucosa located on the roof of the nasal cavity
flavor:
- the impression we experience from the combination of taste and olfaction and several other factors
neurogenesis
constant renewal of the receptors unique to taste and smell
- because they get exposed to harmful materials
olfactory receptors: cycle of birth, development, and death = 5-7 weeks
taste receptors = 1-2 weeks
how do chemical senses act as gatekeepers?
- identify things that the body needs for survival and that should therefore be consumes
- detect things that would be bad for the body and that should therefore be rejected
emotional components of the chemical senses
things that are bad for us often taste or smell unpleasant
things that are good for us generally taste or smell good
smelling an odor associated with a past place or event can trigger memories, which in turn may create emotional reactions
taste quality and substance effect
sodium chloride (salty)
hydrochloric acid (sour)
sucrose (sweet)
quinine (bitter)
potassium chloride (both salty and bitter components)
sodium nitrate (salty, sour, and bitter)
taste quality and associations
sweetness: associated with substances that have nutritive value
bitter: associated with substances that are potentially harmful
salty: presence of sodium
connection isnt perfect
types of papillae on the tongue
filiform: shaped like cones and located over entire surface
fungiform: series of folds on back and sides
foliate: series of folds along the back of the tongue on the sides
circumvilliate: shaped like flat mounds in a trench located at back
where are taste buds located
in papillae (except for filiform)
how many taste buds does the tongue contain?
10,000 taste buds
taste cells in taste buds
each bud has 50-100 taste cells with tips that extend into the taste pore
when does transduction in taste cells occur
when chemicals contact the receptor sites on the tips
what are the four pathways for signals from taste cells
chorda tympani nerve from front and sides of tongue
glossopharymngeal nerve from back of tongue
vague nerve from mouth and throat
superficial petronasal nerve from soft palate
where do taste pathways connect
in the solitary tract in the spinal cord
from there, they go to the thalamus and then to areas in the frontal lobe:
- insula
- frontal opervulum cortex
- orbital frontal cortex
arguments for population coding in taste
Erickson: found that nerve fibers responded in population coding style for different taste stimuli in rats
- also found that similar tastes had similar patterns of firing, as population coding would predict
specificity coding
- we have receptors that respond specifically to a particular taste - ex. adding bitter taste receptors in mice makes them avoid bitter tasting things
- also have neurons that respond selectively to specific stimuli/a number of specific stimuli
- amiloride (a substance that blocks the flow of sodium into taste receptors) - applying it to the tongue of a rate decreases responding to neurons that react to salt, but not others
anosmia
loss of the ability to smell due to injury or infection
papillae
the structures that give the tongue its rough appearance - there are four kinds, each with a different shape
taste buds
contained on the papillae (except filiform) - about 10,000 taste buds
contains 50 to 100 taste cells
taste cells
cells that make up a taste bud - each bud contains a number of cells, and the tip of each one sticks out into a taste pore
one or more nerve fibers are associated with each cell
receptor sites
sites located on the tips of the taste cells
there are different types of sites for different chemicals - chemicals contacting the sites cause transduction by affecting ion flow across the membrane of the taste cell
why does stimulation on the central part of the tongue cause no taste sensations
because it only contains filiform papillae, which have no taste buds
taste pore
an opening in the taste bud through which the tips of taste cells protrude. when chemicals enter a taste pore, they stimulate the taste cells and result in transduction
nucleus of the solitary tract
the nucleus in the brain stem that receives signals from the tongue, the mouth, and the larynx transmitted by the chorda tympani, glossopharyngeal, and vagus nerves
insula
area in the frontal lobe of the cortex that receives signals from the taste system and is also involved in the affective component of the perception of pain
frontal operculum
an area in the frontal lobe of the cortex that receives signals from the taste system
