Sensation and Perception - chemical_senses.ppt © 2001 Dr. Laura Snodgrass, Ph.D.1 The Chemical...

Sensation and Perception - chemical_senses.ppt © 2001 Dr. Laura Snodgrass, Ph.D. 1

The Chemical Senses

• Olfaction and Gustation

• Research difficulties

• Pheromones

• Gustation (taste)– four taste qualities

– flavor

– tongue localization

– survival significance

– sensory coding


The Chemical Senses

• Olfaction (smell)– the basic smells

• Amoore

• Henning’s Odor Prism

– receptor

– coding

– survival significance

– neural pathways


The Chemical Senses

• Olfaction and Gustation– sensory systems for the detection of chemicals

– olfaction (smell) detects chemicals in the air

– gustation detects chemicals dissolved in a solution

• saliva helps to dissolve the chemical

• Research difficulties– hard to control amount of odorant reaching the smell receptors

– very rapid adaptation

– taste buds die off every 4 - 11 days


Pheromones

• Animal studies– chemical communication by both taste and smell

• Human studies– gender identification

• men - musky

• women sweet

– babies can identify own mother’s milk by smell

– family members can identify family t-shirts

– Vomeronasal system

• role of smell is sexual attraction - the perfume industry

– moose musk, and “pheromone” the perfume

• the McClintock effect


Gustation

• Four basic taste qualities– sweet, sour, bitter, salt

• Flavor – not the same as taste

• an apple, onion, and potato all have the same taste, they differ in flavor

– flavor is composed of: taste, smell, touch (texture), temperature, color, and sometimes pain

– learned preferences for flavors


Tongue Localization

The entire surface can detect all tastes.

However, the tip is most sensitive to sweet, the sides to salt and sour, the back of the tongue and the soft palate respond most strongly to bitter.


Survival Significance of Taste

Taste Stimulus Significance

SweetComplex organic

molecules(sugars and carbohydrates)

energy

Salt NACL Nerve conduction

Sour Acids (H+)Spoiled foodor vitamins

BitterOrganic alkaloids

Metallic salts poison


Sensory Coding

• Across fiber pattern coding– the pattern of activity across many

receptors codes for the taste– the same receptors may respond but

with different relative amounts of activity

– the graph shows four sample taste buds and how they might respond to each taste

• Specific tastes are identified in the frontal lobe

0

10

20

30

40

50

60

70

80

90

A B C D

sweet

sour

salt

bitter


Olfaction

• Basic smells– Amoore’s seven basic smells

• camphoraceous

• pungent

• floral

• ethereal

• minty

• musky

• putrid

– all other smells would be a combination of these

– later Amoore had 14 basics, then 21 basics, etc..


Olfaction

Henning’s Odor Prism - a graph of 6 basic smells and their possible combinations


Olfactory Receptor

Olfactory mucosa

(epithelium)


Sensory Coding

• Chromatographic theory (tentative)– spatial pattern

– pattern of activity across many receptors

– different odors cause activity in different locations on the olfactory mucosa

• No one theory has strong evidence to support it


Survival Significance

• Taste acts to detect important nutrients and to warn us about bad food or poison

• How might smell function to:– warn us about danger?

– attract us to things that will help us survive or bring us pleasure?


Neural Pathways

• The olfactory mucosa is directly linked to the olfactory bulb which sends the information to the frontal lobe for identification

• Collaterals (copies of the signals) are send to three other structures– amygdala - where emotions are processed

– hippocampus - where memories are processed

– hypothalamus - processing involved in eating, drinking, and sexual behavior

• Smell is strongly associated with emotions, memory, eating, drinking, and sexual behavior

Sensation and Perception - chemical_senses.ppt © 2001 Dr. Laura Snodgrass, Ph.D.1 The Chemical...

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Transcript of Sensation and Perception - chemical_senses.ppt © 2001 Dr. Laura Snodgrass, Ph.D.1 The Chemical...