Smell

Question 1

What is the olfactory system?

Answer 1

• specialized for identifying specific molecules called odorants

Question 2

What are odorant molecules?

Answer 2

• volatile substances (easily sucked up in air or stay in air a bit)
• have a molecular weight in range of approximately 15 to 300
• most are lipid soluble and of organic origin, however many substances that meet these criteria have no odor

Question 3

What receptor proteins transduce odorants into a change in membrane potential?

Answer 3

• metabotropic g protein-coupled receptors
• humans express ~400 different types of odorant receptors
• each one is sensitive to a specific molecule

Question 4

What is the olfactory epithelium?

Answer 4

• the tissue of the nasal sinus that sits underneath the skull (the cribriform plate)
• contains olfactory receptors cells
• each cell expresses only one type of olfactory receptor protein

Question 5

Where do olfactory receptor cells synapse?

Answer 5

• in glomeruli in the olfactory bulb

Question 6

What is glomerulus?

Answer 6

• processes information from just one type of olfactory receptor cell (expressing a particular type of olfactory receptor protein)
• each glomerulus processes a distinct odor

Question 7

What is the pathway of olfactory information?

Answer 7

• olfactory receptors cells in the olfactory epithelium synapse in glomeruli in the olfactory bulb
• sends axons into brain
• info goes directly to primary olfactory cortex in temporal lobe and the amygdala (does not relay in thalamus)

Question 8

What smells are good and bad?

Answer 8

• odors are largely not hard wired to be innately good or bad
• whether we like or dislike an odor is related to learned associations

Question 9

How many odorants can humans recognize?

Answer 9

• up to ten thousand different odorants