THE NOSE KNOWS:THE NOSE KNOWS: Mammal OlfactionMammal Olfaction

What Is The Olfactory System?What Is The Olfactory System?

The The oolfactory systemlfactory system is a sensory is a sensory system used for system used for olfactionolfaction, or the sense of , or the sense of smell and chemoreception. smell and chemoreception.

ChemoreceptionChemoreception is detection of certain is detection of certain chemical stimuli (chemical stimuli (odorantsodorants ) in the ) in the environment. environment.

Most mammals have two distinct parts to Most mammals have two distinct parts to their olfactory system: their olfactory system: Main Olfactory Main Olfactory BulbBulb and an and an Accessory Olfactory BulbAccessory Olfactory Bulb..

The The Main Olfactory SystemMain Olfactory System ( (bulbbulb) detects volatile, ) detects volatile, airborne substances (airborne substances (chemicalschemicals), while ), while the the Accessory Olfactory BulbAccessory Olfactory Bulb is is receptive to fluid-phase stimuli.receptive to fluid-phase stimuli.

There is a subsystem from the There is a subsystem from the MOSMOS, which is the , which is the VNOVNO or or vermeronasal organvermeronasal organ. AkA . AkA Jacobson’s Jacobson’s OrganOrgan. .

This arose in tetrapods. This arose in tetrapods. Used for pheromone detectionUsed for pheromone detection Separate from the Separate from the MOSMOS but works with in but works with in

conjunction with it to establish necessary conjunction with it to establish necessary behaviorbehavior

There is a tissue layer on the roof of the nasal cavity There is a tissue layer on the roof of the nasal cavity behind the nostrils called the behind the nostrils called the olfactory epitheliumolfactory epithelium. It . It is an epithelial layer of the olfactory system directly is an epithelial layer of the olfactory system directly responsible for detecting odors. responsible for detecting odors.

Jacobson’s OrganJacobson’s Organ

Or the Or the VNOVNO, , vermeronasalvermeronasal organorgan is a chemosensory is a chemosensory organ in the nasal septum of roof of the mouth in organ in the nasal septum of roof of the mouth in vertebrates used for pheromone detectionvertebrates used for pheromone detection

A cat will open its mouth like it’s smiling to allow air into A cat will open its mouth like it’s smiling to allow air into the mouth for maximum chemoreception. This activity the mouth for maximum chemoreception. This activity is called Flehmen Response.is called Flehmen Response.

The information received through this organ goes The information received through this organ goes directly to the thalamus which controls homeostasis, directly to the thalamus which controls homeostasis, apetite and sexual desireapetite and sexual desire

Many mammals do thisMany mammals do this

How well can you smell?How well can you smell?

AnosmiaAnosmia: no sense of smell: no sense of smell HyposmiaHyposmia: decreased sense of smell: decreased sense of smell HyperosmiaHyperosmia: increased sense of smell: increased sense of smell DysosmiaDysosmia: confused sense of smell: confused sense of smell

FUNCTIONFUNCTION

The mechanism of the olfactory system The mechanism of the olfactory system can be divided into a can be divided into a peripheralperipheral one, one, sensing an external sensing an external stimulusstimulus and and encoding it as an electric signal in encoding it as an electric signal in neuronsneurons, and a , and a centralcentral one, where all one, where all signals are integrated and processed in signals are integrated and processed in the the central nervous systemcentral nervous system, causing the , causing the brain to send appropriate signals to the brain to send appropriate signals to the rest of the body to respond accordingly rest of the body to respond accordingly to the stimulus it just received. to the stimulus it just received.

To accomplish all of these functions, To accomplish all of these functions, the olfactory system uses many the olfactory system uses many areas of the brain. Representations of areas of the brain. Representations of the odor may be encoded by the odor may be encoded by spacespace (a pattern of activated (a pattern of activated neuronsneurons across a given olfactory region across a given olfactory region corresponds to the odor), corresponds to the odor), timetime (a (a pattern of pattern of action potentialsaction potentials by by multiple neurons corresponds to the multiple neurons corresponds to the odor) or a combination of the two. odor) or a combination of the two. NeuronsNeurons (also called nerve cells) are (also called nerve cells) are the primary cells of the nervous the primary cells of the nervous systemsystem

The olfactory system does several things:The olfactory system does several things: Create a representation of the odor Create a representation of the odor Determine the concentration of the odor Determine the concentration of the odor Distinguish a new odor from the Distinguish a new odor from the

background environmental odors background environmental odors Identify the odor across different Identify the odor across different

concentrations concentrations Pair the odor with a memory of what the Pair the odor with a memory of what the

odor represents odor represents

Can Fish Smell?Can Fish Smell?

They do have an olfactory system and They do have an olfactory system and the ability of the ability of chemoreceptionchemoreception

They also share with mammals, a They also share with mammals, a sensory epitheliumsensory epithelium and and olfactory bulbolfactory bulb. .

Water enters the olfactory system through an opening in the face called a nare.

WHY SMELL?WHY SMELL?

Most mammals experience their world Most mammals experience their world through their noses. Their life depends through their noses. Their life depends on it. on it.

A Few Reasons To SmellA Few Reasons To Smell

Olfactory messagesOlfactory messages

Species recognitionSpecies recognition Individual recognitionIndividual recognition Group recognitionGroup recognition Mother/Infant recognition Mother/Infant recognition Marking territoryMarking territory Signal Social DominanceSignal Social Dominance Influence the Physiology of othersInfluence the Physiology of others Sexual SignalsSexual Signals

Sources of Olfactory SignalsSources of Olfactory Signals

UrineUrine FecesFeces Gland secretionsGland secretions

Individual RecognitionIndividual Recognition

The Indian Mongoose has analglands that produce 6 differentAcids.

Species RecognitionSpecies Recognition

Group RecognitionGroup Recognition

The Gliding Opossum marks all group members with his male dominant scent

Mother/Infant RecognitionMother/Infant Recognition

A blind newborn kitten will smell the way to its mother and latch on toa teat. At this point smell ensures the kitten’s survival.The safe environment will also allow for normal, healthy development

Lemur marks his territory

Man marks his territoryMan marks his territory

Signaling Social DominanceSignaling Social Dominance

Physiological InfluencePhysiological Influence

Odor in the urine of male mice stimulates female mice to come into estrus

Sexual SignalsSexual Signals

Elephants have temporal lobe secretions (musth)

A Variety of NosesA Variety of Noses

More NosesMore Noses

This is my noseThis is my nose

It’s All About The SnoutIt’s All About The Snout