smell

Question 1

olfactory mucosa

Answer 1

1) patch of mucosa in the ceiling of the nasal cavity
2) contains three cell types
- olfactory receptor cells
- supporting cells
- basal cells

Question 2

cell types

Answer 2

1) supporting cells
- mucus
2) basal cells
- stem cells
3) olfactory cells
- afferent neurons with receptors in the olfactory mucosa
- receptor portion
- enlarged knob bearing long cilia
- cilia extend to the surface of the mucosa, and bind odorants

Question 3

smells

Answer 3

1) there are 5 million olfactory receptors (1000 types)
2) each receptor only binds a specific component of an odorant
- which may have multiple components to activate multiple receptors
3) to be smelled, a substance must be volatile and water soluble

Question 4

smelling pathway

Answer 4

1( odorant binds receptor
2) activates G proteins
3) active adenylate cyclase
4) cAMP increases
5) activates non specific ion channels
6) ion channels open
7) receptor cell depolarizes
8) action potentials are generated
- frequency depends on concentration of odorants

Question 5

olfactory bulbs

Answer 5

1) lined by small, ball-like neural junctions (glomeruli)
2) within each glomerulus: receptor cells synapse with mitral cells
3) each glomerulus receives signals only from receptors that detect a particular odor component
- separate components of an odor are sorted into different glomeruli

Question 6

odor discrimination

Answer 6

1) dependents on number of receptors
- based on different patterns of glomeruli activation
- ability of odorant to bind to receptor contributes as well
2) cortex can distinguish 10,000 scents
3) we have poor sense of smell compared to other species

Question 7

adaptation to smells

Answer 7

1) sensitivity decreases after short period of exposure
- diminishing sensitivity is process in the CNS
2) adaptation is specific for a particular odor
3) responsiveness to other odors remains unchanged

Question 8

removing odors

Answer 8

1) enzymes clear away the odor molecules so they do not continue to stimulate the olfactory receptors
2) the nasal enzymes may also transform harmful molecules into harmless ones
3) similar to liver enzymes

Question 9

cold exposure impairs extracellular vesicle swarm mediated nasal anti-viral immunity

Answer 9

1) virus never goes away
2) our main immunity is impaired in winter months