Physiology of Smell Flashcards
what are the 4 different neural systems mammals have within the left and right sides of the nose
main olfactory system(CN I), trigeminal somatosensory system(CN V), the accessory olfactory system, the nervus terminalis
describe the roles of CN I and CN V in smelling
CN I = mediates common odours(eg rose, chocolate, vanilla)
CN V = chemical and non-chemical stimulus(eg irritation), also protective if sniff something harmful will help to halt inhalation
where is the olfactory neuroepithelium
within small region of the nasal mucosa, 7cm into nasal cavity from nostril
how much inspired air reaches olfactory epithelium and where else does air come from
only 10-15% inspired air
significant amount of retrograde airflow from nasopharynx occurs during swallowing
describe smell during quiet breathing and when sniffing
odorants only reach smell receptors by diffusion, as olfactory mucosa is above the normal path of airflows
sniffing increases airflow and draws air current up to olfactory mucosa
what properties must a substance have in order to be smelled
sufficiently volatile(some of its particles can enter nose in inspired air) sufficiently water soluble(can dissolve in mucous covering olfactory epithelium)
what is the olfactory cleft made up of
cribriform plate and very small parts of the superior and middle turbinate and septum
where must an odour travel before neural conduction can occur
enter nose during activity (sniffing or passive diffusion)
pass to the olfactory cleft
move from air phase to aqueous phase
why is mucus important in olfactory cleft
moist and protective environment, aids in dispersing odourants to olfactory receptors
describe the endings of olfactory receptors and what there axons form
specialised endings of renewable afferent neurons
receptor axons join to form afferent fibres of olfactory nerve
describe where smell information travels from olfactory nerves travel to
nerves pierce the cribriform plate and enter olfactory bulb
from bulb neurons pass along olfactory tract to reach temporal lobe and olfactory areas
what are anosmia and hyposmia
anosmia = loss of smell hyposmia = reduced smell
what are dysosmia and phantosmia
dysosmia = altered sense of smell phantosmia = smell perceived in absence of stimulus
what are some conductive causes of smell symptoms
nasal polyps, rhinitis, nasal mass
what are some sensironeural causes of smell symptoms
viral, head trauma, neurological conditions, brain tumours, medications
