Physiology of smell (pie)

Question 1

What is the primary location for sensing smell ?

Answer 1

Olfactory mucosa – patch of mucosa in the ceiling (dorsal roof) of the nasal cavity

Question 2

What are olfactory receptors and there function/location ?

Answer 2

• Specialised endings of renewable afferent neurons
• Found in the olfactory mucosa of olfactory mucosa, function is to sense smell

Question 3

Describe the structure of the olfactory receptors

Answer 3

• Each neuron has a thick short dendrite and an expanded end called an olfactory rod
• From the olfactory rods, cilia project to the surface of the olfactory mucosa (about 10-12 cilia per olfactory receptor neuron)
• Odorants (molecules that can be smelled) bind to the cilia

Question 4

What do the axons of the olfactory cells collectively form ?

Answer 4

Form afferent fibres (going away back to the brain) of olfactory nerve

Question 5

Describe the route of how impulses from olfactory receptors reach the brain

Answer 5

1. Afferent nerve fibres of the olfactory nerve pierce the cribriform plate
2. Enter the olfactory bulb
3. Olfactory bulb neurons passes along the olfactory tract to reach temporal lobe and olfactory areas

Question 6

By what mode of movement do odorants usually reach the olfactory cells (think about how things move across a plasma membrane)

Answer 6

By diffusion

Question 7

Define what asomnia is and give some examples

Answer 7

Inability to smell - e.g. viral infections; allergy, nasal polyps, head injury etc

Question 8

Define what hyposmia is and give some examples

Answer 8

Reduced ability to smell - e.g. viral infections; allergy, nasal polyps, head injury etc

Question 9

Define what dysosmia is and give some examples

Answer 9

Altered sense of smell - e.g. differently interpreting some odours; and hallucinations of smell