Olfactory Epithelium (Mucosa): mucous has olfactory
binding protein, allows molecules to stick easier.
-Olfactory Receptor Neurons (ORN): have cilia on the
end, important in moving the mucous (or else we loose
sensitivity to smell)
-when we smell, molecules get stuck to the cilia.
-only communicate to one or two kinds of
Glomeruli, pattern of activity on Glomeruli tells us what
substance we are smelling
Disorders of Olfaction
A) Anosmia: smell blindness, makes it impossible to smell
1) Temporary: occurs because of damage to the
olfactory receptor neurons
-can happen from getting hit in the face,
cribform plate gets crushed (snipping off the axon, killing
neuron)
-neurons replace themselves every 5-7
weeks, so a new one will grow in.
-can happen from inhaling shit, like Cocaine or
Zinc
2) Permanent: affects all smells, damage to some part
of the olfactory centre in the brain
-some specific types: people cant smell piss,
sweat, skunk.
-this is because some people lack certain
Olfactory Receptor Proteins (350 types!)
-mice have 1000 olfactory receptor proteins
B) Olfactory Hallucination: when you smell something, but
there is nothing there to be smelled
-certain kinds of viruses will produce this effect
-schizophrenia
Factors that affect Olfactory Thresholds
A) t-butylmercapton: rotten egg smell, we are most
sensitive to this
-put this in natural gas (because gas is odourless)
so we can detect
B) Age: younger kids do not have preference for rich
smells (like aged cheese) that develops later in life
-as you get older, your sense of smell is less and
less sensitive (happens to everyone)
-Alzheimer's disease: affects sense of smell first
C) Gender: women (more estrogen) have lower
thresholds so they are more sensitive to smell.
-Testosterone in males reduces sensitivity and
increases threshold for smell