Smell Flashcards
odor
the translation of a chemical stimulus to smell sensation
odorant
the actual molecule(s) that capable of being translated into smell
odorants must be (3 things)
volatile (able to float through air)
small
hydrophobic (repellent to water)
you don’t smell ___ despite it constantly filling your nose qualifying
air
not perceiving particular odorants may be a mix of (3 things)
evolution, genetics, habituation
primary purpose of your nose
to let you breathe while filtering and warming that air
2 paths for air/olfaction
orthonasal
- direct to your nasal passage, what you use to sniff
retronasal
- odorants pass from your throat back up to your nasal passage
olfactory cleft
a narrow space at the back of the nose where air and odorants flows
olfactory epithelium
a mucous membrane in the cleft that detects odorants in the air
transduction happens here
3 cell types in the olfactory epithelium
olfactory sensory neurons (OSNs)
- transductors
supporting cells
- metabolic and physical support
basal cells
- cells that will eventually become OSNs
OSNs have cilia as well, defined as …
extend surface area for chemical receptors that odorants can bind to
you need _____ molecules/odorants binding to a receptor to initiate an action potential
several!
axons from OSNs pass through bony _______ _____ and form olfactory nerves (cranial nerve I)
cribriform plate
after the cribriform plate, the smell pathway continues in the ____ _____
olfactory bulbs
olfactory bulbs
one per side of nose and brain
ipsilateral
anosmia
the loss of smell
OSNs converge on ________ based on shared receptor types in the olfactory bulb
glomeruli
rule of 1-1-1
each OSN has 1 receptor type, which responds to 1 odorant, and all of that type converge on 1 glomerulus
despite the 1-1-1 rule and only 1000 receptor types, we can detect over ________ smells
one trillion
without a particular receptor, or if it becomes faulty, can have _____ ______ for that odorant
specific anosmia
general order in depth (shallow to deep) for later olfactory bulb cells is…
tufted –> mitral –> granule
tufted and mitral cells code for …
more specific odors and send that info on to brain
granule cells act as …
lateral inhibition circuit
the deeper you go in the olfactory bulb, the more _____ you get
specific
smell signals sent to the ____ ____ _____ which includes portions of the limbic system
primary olfactory cortex
main feature of the limbic system
amygdala - emotion
orbitofrontal cortex (what is this part of?)
bottom part of front of your brain
portions if this are secondary olfactory cortex
secondary olfactory cortex
support your conscious perception of smell as well as assigns affective value to it
smell is the only sense that doesn’t use the ______
thalamus!
why do some smells “hurt”?
nociceptors throughout your nose and eyes can respond to odorants too and produce pain sensations
shape-pattern theory
scents have different odorant shapes that can bind to multiple odorant receptors in a particular pattern
different odorants combine with receptors, bind in pattern that can result in different smells
stereoisomers (what is this evidence for?)
molecules that are mirror images of each other
evidence for temporal component!
smell depends on the pattern of _____ and _____ that odorants bind in
shape; order
we almost always smell _______ of odorants
mixtures
olfaction is a _______ sense
synthetic (mixture)
how are hearing and smell similar?
both have an element of timbre!
3 things involved in olfaction
detection
discrimination
recognition
can detection with smell be trained?
yes
how to test olfactory detection thresholds
staircase method
- smell concentrations that have an ascending or descending amount of an odorant
- mark where person detects or stops detecting odor
what is the staircase method similar to?
method of limits!!
how to test olfactory discrimination?
triangle test
- give 3 mixtures, 2 are the same and 1 is the outlier, see how accurate they are in picking out the odd one
triangle test is similar to …
the vision phenomenon where if your culture has a name for different shades of a color, they will pick out the difference easier than cultures who don’t discriminate between those shades
we are good at being able to ______ a smell but not _____ a smell (why?)
identify; name
why: smell is processed on the right side of the brain while language is on the left
smell is not integrated with other _____ in the thalamus
senses
smell adaption
short term
more sensitive to change
can result in cross-adaption, where one smell blocks the detection of another
cognitive habitutation
long term
ex. becoming used to the smell of your pet around the house
_______ enhances smell detection
attention
you cannot _____ ___ ______ in your sleep
attend to smell
memory card game example with smell
when learning a memory game, you are exposed to a certain odor
when sleeping that night, you are either exposed to the same odor, a different odor, or no odor at all
while being asked to retrieve those memories of the game the next day, people exposed to the same odor while sleeping did better than those exposed to a differing odor or no odor while sleeping
shows smells during sleep can enhance associated memories
odor hedonics
the dimension of odor that involves liking and familiarity
interacts with intensity
whats more intense: the same amount of a pleasant smell or an unpleasant smell?
unpleasant smell
like hearing; smell perception is not the direct product of the _____ _______
physical dimensions
4 factors that impact your threshold for smells
age
sex
hormones
experience
smell loss can be an early sign of …
neurodegenerative disorders like Alzheimer’s and Parkinson’s
