chapter 16: chemical senses Flashcards
define anosmia
loss of sense of taste and smell
name the three components of taste and smell
- taste
- olfaction
- flavour (combination of taste and smell)
what is one property that distinguishes the chemical senses from vision, hearing and the cutaneous senses?
neurogenesis because molecules are exposed to environment
- 5-7 weeks for olfactory receptors
- 1-2 weeks for taste receptors
why are the chemical senses seen as “gatekeepers” of the body
- identify things the body needs for survival (smell/taste good)
- detect things that would be bad for the body (taste/smell unpleasant)
name the 5 basic taste sensation
salty, sour, sweet, bitter, umami
why is sweetness often associated with good components and bitter with bad components
sweet: nutritive + caloric value = automatic acceptance response
bitter: harmful substance = automatic rejection response
what happens when a person is deprived of sodium
seeks out food that taste salty to replenish the salt the body needs
name the four types of papillae that can be found on the tongue
- filiform (cones, entire surface)
- fungiform (mushroom, tip/sides)
- foliate (folds, back)
- circumvallate (flat mounds, back)
which papillae does not contain taste buds
filiform
explain how an electrical signal is generated in the taste cells
stimulus in contact with papillae → taste bud → made of taste cells → tips protrude into taste pore → transduction → electrical signal
name the 4 different types of nerves
- chorda tympani nerve (front and side)
- glossopharyngeal nerve (back)
- vagus nerve (mouth and throat)
- superficial petrosal nerve (top of mouth)
where do the fibers from the tongue, mouth and throat make connections
brain stem in the nucleus of the solitary tract
the primary taste cortex is composed of which part of the brain
insula and frontal operculum
what is another name for population coding
across-fiber patterns
explain the experiment that was done to prove population coding
2 substances with similar pattern should taste the same
- ammonium chloride & potassium chloride similar
- inflicted shock for one of them = avoid the other too
- chooses sodium chloride instead bc different pattern
explain Mueller’s experiment that supports specificity coding
- mice no PTC receptor = don’t avoid (normal)
- mice with PTC receptor = avoid, bitter (cloned)
- mice w Cyx receptor = avoids Cyx (normal)
- mice no Cyx receptor = don’t avoid (cloned)
what is the effect of amiloride
- blocks the flow of sodium into taste receptors
- ↓ neuron response in the brainstem
what mechanisms may be responsible for individual differences in taste
- higher density in taste buds = can taste more
- presence of specialized receptors
differentiate between a microsmatic and macrosmatic person
microsmatic: having poor sense of smell that is not crucial to survival
macrosmatic: having well-developed sense of smell
what method is used to find the detection threshold for odors
forced-choice method
- one trial with weak odorant and other no odorant
- Ps indicate which trial has stronger smell
- threshold = correct response on 75% trials
true or false? difficulty to accurately identify odors results from a deficiency in our olfactory system
false, it results from inability to retrieve the odor’s name from our memory
name some genetically determined individual differences in odor perception
- smell of steroid androsterone different for each person
- sensitive to B-ionone = fragrant, floral
- less sensitivity to B-ionone = sour, pungent, acid
decrease in olfaction is a predictor of which disease
Alzheimer’s
what is one explanation for why COVID causes a decrease in olfaction
COVID molecules attach to ACE2 found in intestines, lungs, arteries, heart and nose
what is the function of sustentacular cells
provide metabolic and structural support to the olfactory sensory neurons
explain the progression of symptoms related to AD
decrease in biomarkers before cognition decrease (MCI)
name two reasons that make it difficult to identify odors
- lack of specific language for odor quality
- molecules with similar structures can smell different and molecules with different structures can smell the same
what are odor objects
coffee, bacon, rose, dog, etc
perceiving odor objects involves 2 stages. what are they
- analyzing (olfactory mucosa and olfactory bulb)
- synthesizing (olfactory cortex)
what is the olfactory mucosa
dimed-sized region located on the roof of the nasal cavity below the olfactory bulb
describe the structure of the olfactory system
molecules in contact with mucosa → contains olfactory receptor neurons (ORNs) → contains olfactory receptors → electrical signal → glomeruli in olfactory bulb
approximately, how many types of olfactory receptors are there?
400
explain the method of calcium imaging
to match odorant to specific ORN
- olfactory receptor responds = ↑ calcium ions
- ↑ calcium ions = ↓ fluoresce glow
- measure ↓ glow to measure how strongly ORN is activated
what is the odorant’s recognition profile
pattern of activation for each odorant
true or false? each glomerulus collects info about the firing of a particular type of ORN
true
name the two main olfactory areas
- piriform cortex
- orbitofrontal cortex
what is the difference in activity between the olfactory bulb and the piriform cortex
odorants cause activity in specific locations in the olfactory bulb but cause widespread activity in PC
- because projection from olfactory bulb is scattered
explain the technique called functional ultrasound imagery
measure change in blood flow to determine brain activation
how does the formation of odor objects occur
- chemotopic map activated
- scattered activation in PC
- learning occurs: links created between scattered activation
explain the Proust effect
ability of odors to trigger autobiographical memories
true or false? in the experiment where Ps were asked to describe an event after being presented with either a picture or an odor, Ps who saw the picture rated their memories as more emotional than Ps who smelled the odor
false
why does odor-evoked memories cause higher activity in the amygdala than word-evoked memories
olfactory nerve is 2 synapses away from amygdala (involved in creating emotions emotional memories) and 3 synapses away from hypothalamus (involved in storing and retrieving memories)
what is the path that chemicals take to go from oral cavities to nasal cavities
retronasal route:
- oral cavity
- nasal pharynx
- choana
- olfactory mucosa
define oral capture
sensations we experience from both olfactory and taste receptors are referred to the mouth
the orbitofrontal cortex contains bimodal neurons. what are they?
neurons that respond to more than one sense
- respond to similar qualities (same neuron that responds for smell and taste of sweet fruits)
what region is considered the cortical center for detecting flavor and for perceptual representation of foods
orbitofrontal cortex
what happens when cognition affects flavor
orbitofrontal cortex receives signal from both olfactory receptors and person’s expectations
what is sensory-specific satiety
decline in pleasantness associated with a food that has been eaten to satiety
- occurs in orbitofrontal cortex
- similar effects in amygdala and insula
differentiate the concepts of correspondence and influence
correspondence: property of a chemical sense is associated with property of other senses
influence: stimuli from one sense affect our perception or performance associated with another sense
