Comprehensive Guide to Taste and Smell: Receptors, Pathways, and Coding

What are the two chemical senses?

Taste (gustation) and smell (olfaction).

Where are taste buds located?

On the tongue (anterior 2/3 and posterior 1/3), roof of the mouth, and pharynx.

How many taste buds are present in the human body?

Over 10,000 taste buds.

What types of cells are found in taste buds?

Taste receptor cells (modified epithelial cells) and support cells.

What are tastants?

Chemicals that activate taste receptor cells.

What are the five primary tastes?

Sour, salty, sweet, bitter, and umami.

What ion is responsible for the sour taste?

Hydrogen ions (H+).

What ion is responsible for the salty taste?

Sodium ions (Na+).

What compounds are associated with the sweet taste?

Small carbohydrates.

What compounds are associated with the bitter taste?

Nitrogen-containing compounds.

What substances are associated with the umami taste?

Glutamate and other amino acids.

What is the coding mechanism for taste perception?

Pattern theory, which involves activation of multiple receptors and neurons.

What cranial nerves are involved in taste sensation?

Cranial nerves VII (Facial), IX (Glossopharyngeal), and X (Vagus).

Where do taste receptor cells synapse?

With afferent neurons that form cranial nerves.

What is the role of the olfactory epithelium?

It contains chemoreceptors that bind airborne chemicals (odorants).

What types of cells are found in the olfactory epithelium?

Receptor cells (bipolar neurons), basal cells, and sustentacular cells.

How do odorants bind to olfactory receptors?

Odorants must be dissolved in mucus to bind to specific olfactory receptor cells.

What is the first step in olfactory signal transduction?

The chemical (odorant) binds to the receptor.

What G protein is activated in olfactory signal transduction?

Golf.

What is the pathway for olfactory signals to the brain?

Olfactory receptor cells → cranial nerve I → olfactory bulb → olfactory cortex and limbic system.

Is there a relay in the thalamus for the primary olfactory pathway?

No, there is no relay in the thalamus.