The chemical senses

Chapter 9

The Taste Bud

Taste Transduction

• Salty – Na+ goes through sodium channels

• Sour – H+ ions block potassium channels

• Sweet – much more complicated (second messenger system)

• Bitter – again complicated, some evidence for interesting genetic differences (PTC and supertasters)

Distribution of taste receptors

Central taste pathways

Olfactory anatomy

Olfactory receptors

Olfactory transduction

Central olfactory pathways

The vomeronasal system – a pathway for pheromones?

McClintock and menstrual synchrony

Women who live together tend to menstruate at the same time

Study 1: diary study of menstrual cycles in 135 Wellesley College dormitory residents

Study 2: direct manipulation by using exposure to odorless axillary secretions influenced length of menstrual cycles

Claus Wedekind and the odour of love

1. The MHC complex is a set of genes that code for proteins that are involved in the immune system

2. It is better to reproduce with individuals whose MHC complex is different to your own

3. The MHC genes also affect the smell of mouse urine4. Female mice prefer the smell of male urine that comes from

critters with a different kind of MHC

Wedekind’s dirty T-shirts

1. Wedekind had men wear T-shirts for 2 days without wearing anything perfumed

2. He then placed them in boxes and asked women to rate the attractiveness of the odour

3. Women preferred the T-shirts of men who had dissimilar MHC complex

“It smells like my boyfriend”4. Not so keen on T-shirts from men

who had similar MHC complex“It smells like my dad”

The progesterone connection

1. In mice, MHC odour preference switches during pregnancy

2. In women using birth control pills, MHC preference also switches