Physiology of Smell (Olfaction) Flashcards
Where is the olfactory mucosa located?
ceiling (dorsal roof) of the nasal cavity
What are olfactory receptors?
specialised endings of renewable afferent neurons
What is the lifespan of olfactory receptors?
2 months
What are the precursors for new olfactory receptors?
basal cells
What is the structure of the afferent neurone?
thick short dendrite
expanded end - olfactory rod
Where are cilia located?
project from the olfactory wall to the surface of the olfactory mucosa
Where do odorants bind?
to the cilia
What are odorants?
molecules that can be smelled
What is the olfactory neural pathway?
1 - axons of the olfactory receptors collectively form afferent fibres of olfactory nerve
2 - afferent fibres of olfactory nerve pierce the cribiform plate of the ethmoid bone and enter the olfactory bulbs in the inferior surface of the brain
3 - olfactory bulbs transmit smell information to the brain
4 - from the olfactory bulb neurons pass along the olfactory tract to reach the temporal lobe and olfactory areas
How do odorants reach the smell receptors during quite breathing?
diffusion - olfactory mucosal is above the normal path of airflow
How does sniffing enhance smelling?
draws air currents upwards within the nasal cavity
What characteristics does a substance require in order to be smelled?
sufficiently volatile - some of its molecules can enter the nose with inspired air
sufficiently water soluble - can dissolve in the mucus coating of the olfactory mucosa
What is anosmia?
inability to smell
What is hyosmia?
reduced ability to smell
Give examples of things that can cause anosmia and hyosmia?
viral infections
allergy
nasal polyps
head injury
