olfactory system - university of south dakotaapps.usd.edu/coglab/schieber/pdf/chemicalsenses.pdf ·...

Olfactory System

Gross Anatomy

Olfactory Epithelium

Olfactory Bulb

Olfactory Transduction

Ascending Pathways

Henning’s Smell Prism

One Face of the Henning Smell Prism

MultiDimensional Scaling

Highly Diverse Smell Thresholds

Odor Identification

Flavor without Smell

Taste

Question: How do we taste? Answer: Like pork. (Anonymous cannibal)

4+1 Taste Primaries

Salty Sour Sweet Bitter Umami

Safe (approach) Acidic; poor nutritional value (avoid) Nutritious (approach) Poisonous (avoid) Amino acids; rich protein source (hearty; savory)

Flavor Perception

Olfaction Taste Texture Temperature Consistency Common chemical sense “heat” of red pepper “coolness” of menthol

Anatomy of the Tongue Papillae; Taste buds; Taste receptor cells; Microvilli

Types of Papillae

Taste “Map” Myth Exposed

Transduction

Sweet; Bitter; Umami G-protein receptor site woven through microvillus wall Taste molecule interacts with G-protein: inhibits ionic flow across membrane; cell depolarizes and starts firing (action potential)

Transduction

Salty Na+ ions diffuse across microvillus wall; depolarizing cell; action potentials generated

Sour H+ ions bind to receptor sites; inhibit K+ pumps; cell depolarizes and generates neural “spikes” [H+] corresponds to acidic strength (i.e., pH)

Receptor / “Labelled Lines” Theory

Taste Pathways

Absolute Threshold

Bitter Quinine 0.000008 M Sour HCl 0.0009 M Salty NaCl 0.01 Molar Sweet Sucrose 0.01 M --------------------------------------------------- Umami Glutamate 0.0007 M

Individual Differences in TB Count [Taste Lab]

Super-Taster Normal Taster

Temperature vs. Sensitivity