Chapter 14 The Chemical Senses Olfaction many kinds

Chapter 14 The Chemical Senses

• Olfaction - many kinds of information • Taste (gustation) - food information • Trigeminal - noxious information

Olfactory System • Anatomy • Olfactory epithelium--> olfactory bulb--> olfatory tract --> pyriform cortex and other forebrain structures, amygdala and hypothalamus.

The map of olfactory processing in the brain • Not really understood

What can we smell? • Airborne odours • Concentration: – e. g. (pizza odour) IBMP, 2 n. M – similar chemical structures are perceived differently, e. g. spearmint and caraway seeds

What can we smell? • Changes with age – E. g. Children smell crayons – Adults, oregano is pleasant

Concentration differences • Floral in low dose is pleasant – Is putrid in high dose

mixtures • Most odours are composed of very many chemicals. – E. g. stawberry odor has about 60 compounds

Old age • Loose ability to correctly identify an odor. • The corresponding region of the brain is not active too.

Physiological and behavioural responses to odours. • Visceral responses: Smell food--> salivation and gastric motility – Noxious smell-->gag

Physiological and behavioural responses to odours. • Reproductive and endocrine functions – Women housed together synchronize menstral cycles – Smelling gauze pads from underarms of women also synchronizes menstral cycles.

Physiological and behavioural responses to odours. • Infants recognize mothers by scent • Mothers can recognize the scent her baby.

Pheromones Species specific odorants. Some pheromones stimulate the vomeronasal organ VNO--> accessory olfactory bulb->hypothalamus. (Found in 8% of human adults), VNO receptors are pseudogenes in humans.

Olfactory receptor (sensory) neuron • In the olfactory epithelium • Have cilia projecting into the nasal cavity mucus • These cells become damaged, and turnover.

Transduction

Two olfactory subsystems • Main • Vomeronasal