Olfactory System

What is olfaction?

smell

What type of sense is olfaction?

chemical sense

What are the physical stimulants and where do they go?

odorants, the nose

Where do the molecules reach?

olfactory receptors high up in your nasal cavity

How are odor molecules detected?

by olfactory receptor neurons

Where are olfactory receptor neurons found?

In the nasal cavity

What do the olfactory receptor neurons contain?

dendrites with cilia and axons

where do the olfactory dendrites extend into?

The olfactory epithelium

Where do the axons of olfactory recepotor neurons projects to>

the olfactory bulb

What does each olfactory receptor neuron express?

One type of odorant receptor

Why does each olfactory receptor neuron express one type of odorant receptor?

so each neuron is tuned to detect molecules that fit one receptor

Do most odor molecules activate one or several receptors?

several receptors at once

patch of specialized tissue high in the roof of nasal cavity

olfactory epithelium

The thin layer of mucus in the olfactory epithelium is secreted by

Bowman’s glands

What happens to odor molecules in the Bowman’s glands

dissolve in mucus and bind to receptors

What mechanisms help maintain the integrity of the olfactory epithelium.

mucus traps and neutralizes harmful particles
immunoglobuins are secreted into the mucus
receptors are replace every 6-8 weeks

How often are receptors replaced?

6-8 weeks

What type of receptors are olfactory receptor neurons?

metabotropic

What does odorant binding activate?

a G-protein which initates an intracellular cascade

What is the target of the olfactory nerve?

olfactory bulb

What happens when the olfactory receptor axons leave the olfactory epithelium>

merge to form the olfactory nerve

What does the olfactory nerve organize?

the input in structures called glomeruli

What does the olfactory bulb do with the axons from olfactory sensory neurons

converge and synapse together into glomeruli

How are odors encoded?

by a pattern of which glomeruli are active

Does information in the olfactory system pass through the thalamus?

no

Where do axons from the olfactory bulb travel to?

primary olfactory cortex

where is the primary olfactory cortex

inferior and medial part of temporal lobe

What are the regions of the primary olfactory cortex?

Piriform cortex
Olfactory tubercle
Sub-region of amygdala
Entorhinal cortex

What handles major odor processing?

Piriform Cortex

What handles early odor processing?

Olfactory tubercule

What associates smells to emotional responses?

Sub-region of the amygdala

What interacts with the hippocampus

entorhinal cortex

the inability to identify common odors

Ansomia

Does olfactory sensitivity decline with age?

yes