4. Chemical senses

Question 1

What are the two primary chemical senses?

Answer 1

Smell (olfaction) and taste (gustation)

These senses help us respond to our external environment.

Question 2

What important behaviors are enabled by chemical senses?

Answer 2

• Food seeking
• Predator avoidance
• Assessing food quality
• Detecting toxins

These behaviors are crucial for survival.

Question 3

What is the anatomical location of olfactory receptor neurons (ORNs)?

Answer 3

In the olfactory epithelium, located in the roof of the nasal cavity

ORNs are essential for the sense of smell.

Question 4

What is the lifespan of olfactory receptor neurons (ORNs)?

Answer 4

6-8 weeks

ORNs are replaced by stem cells in the epithelium.

Question 5

What type of receptors do odorants bind to in the olfactory system?

Answer 5

G-protein coupled receptors (GPCRs)

These receptors are located in the cilia of ORNs.

Question 6

What molecule does adenylyl cyclase convert ATP into during olfactory transduction?

Answer 6

Cyclic AMP (cAMP)

This conversion is a key step in the transduction mechanism.

Question 7

What ions are allowed to influx when cAMP opens cyclic nucleotide-gated ion channels?

Answer 7

• Calcium
• Sodium

This influx creates a graded potential in ORNs.

Question 8

What coding mechanism does olfaction use to encode odor information?

Answer 8

Cross-fiber pattern coding

Different odorants activate various patterns across ORN populations.

Question 9

How many olfactory receptor neurons (ORNs) typically send axons to a single glomerulus?

Answer 9

~25,000 ORNs

This collective input is essential for odor processing.

Question 10

What is the primary olfactory cortex called?

Answer 10

Piriform cortex

It is one of the key brain regions for processing olfactory signals.

Question 11

Which brain region is involved in emotional processing related to olfaction?

Answer 11

Amygdala

This area connects emotions with smells.

Question 12

Which brain region connects to the hippocampus for memory in relation to olfactory signals?

Answer 12

Entorhinal cortex

This connection is important for memory formation related to odors.

Question 13

True or False: Olfactory information first goes through the thalamus like other sensory systems.

Answer 13

False

Olfactory information bypasses the thalamus.

Question 14

What is unique about the organization of information in the piriform cortex compared to other sensory systems?

Answer 14

It doesn’t appear to have clear topographic mapping

This contrasts with the organization seen in other sensory modalities.