Chemo senses

Taste and Smell

detect airborne chemicals

detect chemicals dissolved in saliva

Chemosenses provide survival value for animals

Some molecules can have same structures, but different “smells”

Others can have different structures and be id’d as same smell

350 types of olfactory receptors, each sensitive to a particular group of odors.

Each olfactory receptor neuron contains only 1 type of olfactory receptor.

Fatty, soapy

Fatty, cheese,dairy

Orange, rose, waxy

Fatty, cheesy, waxy

Almond

The functional grpasocc. w/ a compound (COOH for acids; OH for alcohols) determines the general area of the olfactory bulb that is activated, and the compounds length determines the position of the area.

Rats can distinguish betwn the 2 forms of Carvone, but not Limoene.

Others are more complex due to downstream processing.

Now add other odors, w/ their 100’s of molecules. We will not experience a jumble…here we’ll smell coffee, bacon eggs!!!

Onion smell labeled pizza perceived more positively than one labeled body odor

Activity pattern in olfactory receptors the same. The label changed perception & this was reflected in different activity of secondary ctx.

– All over, no taste buds

– Tip & sides

– Folds along back & sides

fungiform

folaite

• Site of transduction

• Each receptor cell responds to a ltd # of molecule types.

• Receptors synapse w/ 3 cranial nerves

– These also carry non-taste info such as pain &tmp

• Rat studies indicate some taste perception is based on distributed coding.

• Chemicals that produced similar firing patterns were perceived as the same (red & green lines)

• Involves taste & olfaction

• Orbitofrontalctx combines taste, olfaction, primary somatosensory &what pathway

• Has neurons that respond to both taste & smell; others taste & vision

• Often respond to similar qualities (smell of sweet & taste of sweet)

• A.L. Fox (worked for DuPont) prepped some PTC., co-worker c/o bitter taste from dust….Fox tasted nothing.

• A.F Blaheslee ( a geneticist) dispensed PTC to 2500 Ss at a conference.– 28%: “tasteless”– 66% “bitter”

Why?

– Different # of receptors

– Some have specialized neurons