special senses-the chemical senses pt.2

what is olfaction?

the sense of smell, response to airbrone chemicals called odorants

what are airborne chemicals that stimulate the sense of smell?

odorants

where are olfactory receptor cells located?

Olfactory mucosa, which is a patch of epithelium in the roof of the nasal cavity

how many different types of olfactory receptors do humans have?

about 400 types

can each olfactory receptor cell detect multiple odorants?

no, each olfactory receptor cell is specialized to detect only one specific chemical odorant

how many odors can humans distinguish?

between 2,000 to 4,000 odors but some can detect up to 10,000

How does a humans sense of smell compare to that of a dog?

dogs can smell with much greater intensity but humans can smell more complex smells

what is the first step in smelling?

the odorant molecule binds to a receptor on the olfactory hairs of the olfactory cells

what is the key feature of how smell works that involves a second messenger system?

the odorant binds to G-protein coupled receptor, activating the cAMP second messenger system

what happens after the second messenger system is activated in the olfactory cell?

ion channels open for sodium and calcium, causing depolarization and triggering an action potential

what is the role of mitral and tufted cells in olfaction?

they consolidate information from the olfactory receptor cells and send it to the brain

where do the mitral and tufted cell axons carry their output?

to the olfactory tracts, which end in the primary olfactory cortex of the brain

what is the first-order neuron in olfaction?

from the olfactory receptor to the glomerulus in the olfactory bulb

what is the second order neuron in olfaction?

from the olfactory bulb’s glomerulus to the primary olfactory cortex

what part of the brain creates conscious perception of smell?

primary olfactory cortex in the temporal lobe

what makes the olfaction pathway unique among special senses?

It skips the thalamus and goes straight to the cortex

what do the olfactory tracts do?

they relay signals caudally from the olfactory bulb to the primary olfactory cortex