The Chemical Senses: Taste and Smell

Chemical Senses

The sensory systems of gustation (taste) and olfaction (smell).

Taste vs. Flavor

Taste is specific receptor sensation; flavor is the combination of taste and aroma.

5 Basic Tastes

Saltiness, sourness, sweetness, bitterness, and umami.

Papillae Types

Filiform (cone), fungiform (sides/tip), foliate (folds), and circumvallate (mounds).

Taste Bud Structure

Clusters of about 50 taste receptor cells with microvilli extending into the taste pore.

Saltiness Transduction

Na+ enters selective ion channels; blocked by the drug amiloride.

Sourness Transduction

H+ ions block K+ leak channels, depolarizing the cell to release serotonin.

Bitterness Receptors

T2R family GPCRs that trigger internal calcium release and ATP secretion.

Sweetness Receptors

G-protein-coupled receptors formed by the T1R2 + T1R3 combination.

Umami Receptors

G-protein-coupled receptors formed by the T1R1 + T1R3 combination.

Primary Gustatory Cortex

Located in the insular cortex; responsible for identifying taste sensations.

Ageusia

The complete loss of the sense of taste.

Anosmia

The inability to perceive smell.

Cribriform Plate

A thin sheet of bone through which olfactory axons pass to the olfactory bulb.

Olfactory Nerve

Cranial Nerve I, formed by the axons of olfactory receptor cells.

Glomerulus (Olfactory Bulb)

Spherical structure receiving input from receptor cells expressing a specific olfactory protein.

Pyriform Cortex

The primary olfactory cortex located in the temporal lobe.

Vomeronasal Organ (VNO)

Distinct sensory organ specialized for detecting pheromones.

Flehmen Response

Animal behavior of curling the lip to draw pheromones into the vomeronasal organ.